New upstream version 2.2.4.4

1 files changed, 2164 insertions, 0 deletions

diff --git a/opusfile/opusfile.h b/opusfile/opusfile.h
new file mode 100644
index 0000000..1e753fa
--- /dev/null
+++ b/opusfile/opusfile.h
@@ -0,0 +1,2164 @@
+/********************************************************************
+ *                                                                  *
+ * THIS FILE IS PART OF THE libopusfile SOFTWARE CODEC SOURCE CODE. *
+ * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
+ * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
+ * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
+ *                                                                  *
+ * THE libopusfile SOURCE CODE IS (C) COPYRIGHT 1994-2012           *
+ * by the Xiph.Org Foundation and contributors http://www.xiph.org/ *
+ *                                                                  *
+ ********************************************************************
+
+ function: stdio-based convenience library for opening/seeking/decoding
+ last mod: $Id: vorbisfile.h 17182 2010-04-29 03:48:32Z xiphmont $
+
+ ********************************************************************/
+#if !defined(_opusfile_h)
+# define _opusfile_h (1)
+
+/**\mainpage
+   \section Introduction
+
+   This is the documentation for the <tt>libopusfile</tt> C API.
+
+   The <tt>libopusfile</tt> package provides a convenient high-level API for
+    decoding and basic manipulation of all Ogg Opus audio streams.
+   <tt>libopusfile</tt> is implemented as a layer on top of Xiph.Org's
+    reference
+    <tt><a href="https://www.xiph.org/ogg/doc/libogg/reference.html">libogg</a></tt>
+    and
+    <tt><a href="https://mf4.xiph.org/jenkins/view/opus/job/opus/ws/doc/html/index.html">libopus</a></tt>
+    libraries.
+
+   <tt>libopusfile</tt> provides several sets of built-in routines for
+    file/stream access, and may also use custom stream I/O routines provided by
+    the embedded environment.
+   There are built-in I/O routines provided for ANSI-compliant
+    <code>stdio</code> (<code>FILE *</code>), memory buffers, and URLs
+    (including <file:> URLs, plus optionally <http:> and <https:> URLs).
+
+   \section Organization
+
+   The main API is divided into several sections:
+   - \ref stream_open_close
+   - \ref stream_info
+   - \ref stream_decoding
+   - \ref stream_seeking
+
+   Several additional sections are not tied to the main API.
+   - \ref stream_callbacks
+   - \ref header_info
+   - \ref error_codes
+
+   \section Overview
+
+   The <tt>libopusfile</tt> API always decodes files to 48&nbsp;kHz.
+   The original sample rate is not preserved by the lossy compression, though
+    it is stored in the header to allow you to resample to it after decoding
+    (the <tt>libopusfile</tt> API does not currently provide a resampler,
+    but the
+    <a href="http://www.speex.org/docs/manual/speex-manual/node7.html#SECTION00760000000000000000">the
+    Speex resampler</a> is a good choice if you need one).
+   In general, if you are playing back the audio, you should leave it at
+    48&nbsp;kHz, provided your audio hardware supports it.
+   When decoding to a file, it may be worth resampling back to the original
+    sample rate, so as not to surprise users who might not expect the sample
+    rate to change after encoding to Opus and decoding.
+
+   Opus files can contain anywhere from 1 to 255 channels of audio.
+   The channel mappings for up to 8 channels are the same as the
+    <a href="http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-800004.3.9">Vorbis
+    mappings</a>.
+   A special stereo API can convert everything to 2 channels, making it simple
+    to support multichannel files in an application which only has stereo
+    output.
+   Although the <tt>libopusfile</tt> ABI provides support for the theoretical
+    maximum number of channels, the current implementation does not support
+    files with more than 8 channels, as they do not have well-defined channel
+    mappings.
+
+   Like all Ogg files, Opus files may be "chained".
+   That is, multiple Opus files may be combined into a single, longer file just
+    by concatenating the original files.
+   This is commonly done in internet radio streaming, as it allows the title
+    and artist to be updated each time the song changes, since each link in the
+    chain includes its own set of metadata.
+
+   <tt>libopusfile</tt> fully supports chained files.
+   It will decode the first Opus stream found in each link of a chained file
+    (ignoring any other streams that might be concurrently multiplexed with it,
+    such as a video stream).
+
+   The channel count can also change between links.
+   If your application is not prepared to deal with this, it can use the stereo
+    API to ensure the audio from all links will always get decoded into a
+    common format.
+   Since <tt>libopusfile</tt> always decodes to 48&nbsp;kHz, you do not have to
+    worry about the sample rate changing between links (as was possible with
+    Vorbis).
+   This makes application support for chained files with <tt>libopusfile</tt>
+    very easy.*/
+
+# if defined(__cplusplus)
+extern "C" {
+# endif
+
+# include <stdarg.h>
+# include <stdio.h>
+# include "../libogg/ogg.h"
+# include <opus/opus_multistream.h>
+
+/**@cond PRIVATE*/
+
+/*Enable special features for gcc and gcc-compatible compilers.*/
+# if !defined(OP_GNUC_PREREQ)
+#  if defined(__GNUC__)&&defined(__GNUC_MINOR__)
+#   define OP_GNUC_PREREQ(_maj,_min) \
+ ((__GNUC__<<16)+__GNUC_MINOR__>=((_maj)<<16)+(_min))
+#  else
+#   define OP_GNUC_PREREQ(_maj,_min) 0
+#  endif
+# endif
+
+# if OP_GNUC_PREREQ(4,0)
+#  pragma GCC visibility push(default)
+# endif
+
+typedef struct OpusHead          OpusHead;
+typedef struct OpusTags          OpusTags;
+typedef struct OpusPictureTag    OpusPictureTag;
+typedef struct OpusServerInfo    OpusServerInfo;
+typedef struct OpusFileCallbacks OpusFileCallbacks;
+typedef struct OggOpusFile       OggOpusFile;
+
+/*Warning attributes for libopusfile functions.*/
+# if OP_GNUC_PREREQ(3,4)
+#  define OP_WARN_UNUSED_RESULT __attribute__((__warn_unused_result__))
+# else
+#  define OP_WARN_UNUSED_RESULT
+# endif
+# if OP_GNUC_PREREQ(3,4)
+#  define OP_ARG_NONNULL(_x) __attribute__((__nonnull__(_x)))
+# else
+#  define OP_ARG_NONNULL(_x)
+# endif
+
+/**@endcond*/
+
+/**\defgroup error_codes Error Codes*/
+/*@{*/
+/**\name List of possible error codes
+   Many of the functions in this library return a negative error code when a
+    function fails.
+   This list provides a brief explanation of the common errors.
+   See each individual function for more details on what a specific error code
+    means in that context.*/
+/*@{*/
+
+/**A request did not succeed.*/
+#define OP_FALSE         (-1)
+/*Currently not used externally.*/
+#define OP_EOF           (-2)
+/**There was a hole in the page sequence numbers (e.g., a page was corrupt or
+    missing).*/
+#define OP_HOLE          (-3)
+/**An underlying read, seek, or tell operation failed when it should have
+    succeeded.*/
+#define OP_EREAD         (-128)
+/**A <code>NULL</code> pointer was passed where one was unexpected, or an
+    internal memory allocation failed, or an internal library error was
+    encountered.*/
+#define OP_EFAULT        (-129)
+/**The stream used a feature that is not implemented, such as an unsupported
+    channel family.*/
+#define OP_EIMPL         (-130)
+/**One or more parameters to a function were invalid.*/
+#define OP_EINVAL        (-131)
+/**A purported Ogg Opus stream did not begin with an Ogg page, a purported
+    header packet did not start with one of the required strings, "OpusHead" or
+    "OpusTags", or a link in a chained file was encountered that did not
+    contain any logical Opus streams.*/
+#define OP_ENOTFORMAT    (-132)
+/**A required header packet was not properly formatted, contained illegal
+    values, or was missing altogether.*/
+#define OP_EBADHEADER    (-133)
+/**The ID header contained an unrecognized version number.*/
+#define OP_EVERSION      (-134)
+/*Currently not used at all.*/
+#define OP_ENOTAUDIO     (-135)
+/**An audio packet failed to decode properly.
+   This is usually caused by a multistream Ogg packet where the durations of
+    the individual Opus packets contained in it are not all the same.*/
+#define OP_EBADPACKET    (-136)
+/**We failed to find data we had seen before, or the bitstream structure was
+    sufficiently malformed that seeking to the target destination was
+    impossible.*/
+#define OP_EBADLINK      (-137)
+/**An operation that requires seeking was requested on an unseekable stream.*/
+#define OP_ENOSEEK       (-138)
+/**The first or last granule position of a link failed basic validity checks.*/
+#define OP_EBADTIMESTAMP (-139)
+
+/*@}*/
+/*@}*/
+
+/**\defgroup header_info Header Information*/
+/*@{*/
+
+/**The maximum number of channels in an Ogg Opus stream.*/
+#define OPUS_CHANNEL_COUNT_MAX (255)
+
+/**Ogg Opus bitstream information.
+   This contains the basic playback parameters for a stream, and corresponds to
+    the initial ID header packet of an Ogg Opus stream.*/
+struct OpusHead{
+  /**The Ogg Opus format version, in the range 0...255.
+     The top 4 bits represent a "major" version, and the bottom four bits
+      represent backwards-compatible "minor" revisions.
+     The current specification describes version 1.
+     This library will recognize versions up through 15 as backwards compatible
+      with the current specification.
+     An earlier draft of the specification described a version 0, but the only
+      difference between version 1 and version 0 is that version 0 did
+      not specify the semantics for handling the version field.*/
+  int           version;
+  /**The number of channels, in the range 1...255.*/
+  int           channel_count;
+  /**The number of samples that should be discarded from the beginning of the
+      stream.*/
+  unsigned      pre_skip;
+  /**The sampling rate of the original input.
+     All Opus audio is coded at 48 kHz, and should also be decoded at 48 kHz
+      for playback (unless the target hardware does not support this sampling
+      rate).
+     However, this field may be used to resample the audio back to the original
+      sampling rate, for example, when saving the output to a file.*/
+  opus_uint32   input_sample_rate;
+  /**The gain to apply to the decoded output, in dB, as a Q8 value in the range
+      -32768...32767.
+     The <tt>libopusfile</tt> API will automatically apply this gain to the
+      decoded output before returning it, scaling it by
+      <code>pow(10,output_gain/(20.0*256))</code>.
+     You can adjust this behavior with op_set_gain_offset().*/
+  int           output_gain;
+  /**The channel mapping family, in the range 0...255.
+     Channel mapping family 0 covers mono or stereo in a single stream.
+     Channel mapping family 1 covers 1 to 8 channels in one or more streams,
+      using the Vorbis speaker assignments.
+     Channel mapping family 255 covers 1 to 255 channels in one or more
+      streams, but without any defined speaker assignment.*/
+  int           mapping_family;
+  /**The number of Opus streams in each Ogg packet, in the range 1...255.*/
+  int           stream_count;
+  /**The number of coupled Opus streams in each Ogg packet, in the range
+      0...127.
+     This must satisfy <code>0 <= coupled_count <= stream_count</code> and
+      <code>coupled_count + stream_count <= 255</code>.
+     The coupled streams appear first, before all uncoupled streams, in an Ogg
+      Opus packet.*/
+  int           coupled_count;
+  /**The mapping from coded stream channels to output channels.
+     Let <code>index=mapping[k]</code> be the value for channel <code>k</code>.
+     If <code>index<2*coupled_count</code>, then it refers to the left channel
+      from stream <code>(index/2)</code> if even, and the right channel from
+      stream <code>(index/2)</code> if odd.
+     Otherwise, it refers to the output of the uncoupled stream
+      <code>(index-coupled_count)</code>.*/
+  unsigned char mapping[OPUS_CHANNEL_COUNT_MAX];
+};
+
+/**The metadata from an Ogg Opus stream.
+
+   This structure holds the in-stream metadata corresponding to the 'comment'
+    header packet of an Ogg Opus stream.
+   The comment header is meant to be used much like someone jotting a quick
+    note on the label of a CD.
+   It should be a short, to the point text note that can be more than a couple
+    words, but not more than a short paragraph.
+
+   The metadata is stored as a series of (tag, value) pairs, in length-encoded
+    string vectors, using the same format as Vorbis (without the final "framing
+    bit"), Theora, and Speex, except for the packet header.
+   The first occurrence of the '=' character delimits the tag and value.
+   A particular tag may occur more than once, and order is significant.
+   The character set encoding for the strings is always UTF-8, but the tag
+    names are limited to ASCII, and treated as case-insensitive.
+   See <a href="http://www.xiph.org/vorbis/doc/v-comment.html">the Vorbis
+    comment header specification</a> for details.
+
+   In filling in this structure, <tt>libopusfile</tt> will null-terminate the
+    #user_comments strings for safety.
+   However, the bitstream format itself treats them as 8-bit clean vectors,
+    possibly containing NUL characters, so the #comment_lengths array should be
+    treated as their authoritative length.
+
+   This structure is binary and source-compatible with a
+    <code>vorbis_comment</code>, and pointers to it may be freely cast to
+    <code>vorbis_comment</code> pointers, and vice versa.
+   It is provided as a separate type to avoid introducing a compile-time
+    dependency on the libvorbis headers.*/
+struct OpusTags{
+  /**The array of comment string vectors.*/
+  char **user_comments;
+  /**An array of the corresponding length of each vector, in bytes.*/
+  int   *comment_lengths;
+  /**The total number of comment streams.*/
+  int    comments;
+  /**The null-terminated vendor string.
+     This identifies the software used to encode the stream.*/
+  char  *vendor;
+};
+
+/**\name Picture tag image formats*/
+/*@{*/
+
+/**The MIME type was not recognized, or the image data did not match the
+    declared MIME type.*/
+#define OP_PIC_FORMAT_UNKNOWN (-1)
+/**The MIME type indicates the image data is really a URL.*/
+#define OP_PIC_FORMAT_URL     (0)
+/**The image is a JPEG.*/
+#define OP_PIC_FORMAT_JPEG    (1)
+/**The image is a PNG.*/
+#define OP_PIC_FORMAT_PNG     (2)
+/**The image is a GIF.*/
+#define OP_PIC_FORMAT_GIF     (3)
+
+/*@}*/
+
+/**The contents of a METADATA_BLOCK_PICTURE tag.*/
+struct OpusPictureTag{
+  /**The picture type according to the ID3v2 APIC frame:
+     <ol start="0">
+     <li>Other</li>
+     <li>32x32 pixels 'file icon' (PNG only)</li>
+     <li>Other file icon</li>
+     <li>Cover (front)</li>
+     <li>Cover (back)</li>
+     <li>Leaflet page</li>
+     <li>Media (e.g. label side of CD)</li>
+     <li>Lead artist/lead performer/soloist</li>
+     <li>Artist/performer</li>
+     <li>Conductor</li>
+     <li>Band/Orchestra</li>
+     <li>Composer</li>
+     <li>Lyricist/text writer</li>
+     <li>Recording Location</li>
+     <li>During recording</li>
+     <li>During performance</li>
+     <li>Movie/video screen capture</li>
+     <li>A bright colored fish</li>
+     <li>Illustration</li>
+     <li>Band/artist logotype</li>
+     <li>Publisher/Studio logotype</li>
+     </ol>
+     Others are reserved and should not be used.
+     There may only be one each of picture type 1 and 2 in a file.*/
+  opus_int32     type;
+  /**The MIME type of the picture, in printable ASCII characters 0x20-0x7E.
+     The MIME type may also be <code>"-->"</code> to signify that the data part
+      is a URL pointing to the picture instead of the picture data itself.
+     In this case, a terminating NUL is appended to the URL string in #data,
+      but #data_length is set to the length of the string excluding that
+      terminating NUL.*/
+  char          *mime_type;
+  /**The description of the picture, in UTF-8.*/
+  char          *description;
+  /**The width of the picture in pixels.*/
+  opus_uint32    width;
+  /**The height of the picture in pixels.*/
+  opus_uint32    height;
+  /**The color depth of the picture in bits-per-pixel (<em>not</em>
+      bits-per-channel).*/
+  opus_uint32    depth;
+  /**For indexed-color pictures (e.g., GIF), the number of colors used, or 0
+      for non-indexed pictures.*/
+  opus_uint32    colors;
+  /**The length of the picture data in bytes.*/
+  opus_uint32    data_length;
+  /**The binary picture data.*/
+  unsigned char *data;
+  /**The format of the picture data, if known.
+     One of
+     <ul>
+     <li>#OP_PIC_FORMAT_UNKNOWN,</li>
+     <li>#OP_PIC_FORMAT_URL,</li>
+     <li>#OP_PIC_FORMAT_JPEG,</li>
+     <li>#OP_PIC_FORMAT_PNG, or</li>
+     <li>#OP_PIC_FORMAT_GIF.</li>
+     </ul>*/
+  int            format;
+};
+
+/**\name Functions for manipulating header data
+
+   These functions manipulate the #OpusHead and #OpusTags structures,
+    which describe the audio parameters and tag-value metadata, respectively.
+   These can be used to query the headers returned by <tt>libopusfile</tt>, or
+    to parse Opus headers from sources other than an Ogg Opus stream, provided
+    they use the same format.*/
+/*@{*/
+
+/**Parses the contents of the ID header packet of an Ogg Opus stream.
+   \param[out] _head Returns the contents of the parsed packet.
+                     The contents of this structure are untouched on error.
+                     This may be <code>NULL</code> to merely test the header
+                      for validity.
+   \param[in]  _data The contents of the ID header packet.
+   \param      _len  The number of bytes of data in the ID header packet.
+   \return 0 on success or a negative value on error.
+   \retval #OP_ENOTFORMAT If the data does not start with the "OpusHead"
+                           string.
+   \retval #OP_EVERSION   If the version field signaled a version this library
+                           does not know how to parse.
+   \retval #OP_EIMPL      If the channel mapping family was 255, which general
+                           purpose players should not attempt to play.
+   \retval #OP_EBADHEADER If the contents of the packet otherwise violate the
+                           Ogg Opus specification:
+                          <ul>
+                           <li>Insufficient data,</li>
+                           <li>Too much data for the known minor versions,</li>
+                           <li>An unrecognized channel mapping family,</li>
+                           <li>Zero channels or too many channels,</li>
+                           <li>Zero coded streams,</li>
+                           <li>Too many coupled streams, or</li>
+                           <li>An invalid channel mapping index.</li>
+                          </ul>*/
+OP_WARN_UNUSED_RESULT int opus_head_parse(OpusHead *_head,
+ const unsigned char *_data,size_t _len) OP_ARG_NONNULL(2);
+
+/**Converts a granule position to a sample offset for a given Ogg Opus stream.
+   The sample offset is simply <code>_gp-_head->pre_skip</code>.
+   Granule position values smaller than OpusHead#pre_skip correspond to audio
+    that should never be played, and thus have no associated sample offset.
+   This function returns -1 for such values.
+   This function also correctly handles extremely large granule positions,
+    which may have wrapped around to a negative number when stored in a signed
+    ogg_int64_t value.
+   \param _head The #OpusHead information from the ID header of the stream.
+   \param _gp   The granule position to convert.
+   \return The sample offset associated with the given granule position
+            (counting at a 48 kHz sampling rate), or the special value -1 on
+            error (i.e., the granule position was smaller than the pre-skip
+            amount).*/
+ogg_int64_t opus_granule_sample(const OpusHead *_head,ogg_int64_t _gp)
+ OP_ARG_NONNULL(1);
+
+/**Parses the contents of the 'comment' header packet of an Ogg Opus stream.
+   \param[out] _tags An uninitialized #OpusTags structure.
+                     This returns the contents of the parsed packet.
+                     The contents of this structure are untouched on error.
+                     This may be <code>NULL</code> to merely test the header
+                      for validity.
+   \param[in]  _data The contents of the 'comment' header packet.
+   \param      _len  The number of bytes of data in the 'info' header packet.
+   \retval 0              Success.
+   \retval #OP_ENOTFORMAT If the data does not start with the "OpusTags"
+                           string.
+   \retval #OP_EBADHEADER If the contents of the packet otherwise violate the
+                           Ogg Opus specification.
+   \retval #OP_EFAULT     If there wasn't enough memory to store the tags.*/
+OP_WARN_UNUSED_RESULT int opus_tags_parse(OpusTags *_tags,
+ const unsigned char *_data,size_t _len) OP_ARG_NONNULL(2);
+
+/**Performs a deep copy of an #OpusTags structure.
+   \param _dst The #OpusTags structure to copy into.
+               If this function fails, the contents of this structure remain
+                untouched.
+   \param _src The #OpusTags structure to copy from.
+   \retval 0          Success.
+   \retval #OP_EFAULT If there wasn't enough memory to copy the tags.*/
+int opus_tags_copy(OpusTags *_dst,const OpusTags *_src) OP_ARG_NONNULL(1);
+
+/**Initializes an #OpusTags structure.
+   This should be called on a freshly allocated #OpusTags structure before
+    attempting to use it.
+   \param _tags The #OpusTags structure to initialize.*/
+void opus_tags_init(OpusTags *_tags) OP_ARG_NONNULL(1);
+
+/**Add a (tag, value) pair to an initialized #OpusTags structure.
+   \note Neither opus_tags_add() nor opus_tags_add_comment() support values
+    containing embedded NULs, although the bitstream format does support them.
+   To add such tags, you will need to manipulate the #OpusTags structure
+    directly.
+   \param _tags  The #OpusTags structure to add the (tag, value) pair to.
+   \param _tag   A NUL-terminated, case-insensitive, ASCII string containing
+                  the tag to add (without an '=' character).
+   \param _value A NUL-terminated UTF-8 containing the corresponding value.
+   \return 0 on success, or a negative value on failure.
+   \retval #OP_EFAULT An internal memory allocation failed.*/
+int opus_tags_add(OpusTags *_tags,const char *_tag,const char *_value)
+ OP_ARG_NONNULL(1) OP_ARG_NONNULL(2) OP_ARG_NONNULL(3);
+
+/**Add a comment to an initialized #OpusTags structure.
+   \note Neither opus_tags_add_comment() nor opus_tags_add() support comments
+    containing embedded NULs, although the bitstream format does support them.
+   To add such tags, you will need to manipulate the #OpusTags structure
+    directly.
+   \param _tags    The #OpusTags structure to add the comment to.
+   \param _comment A NUL-terminated UTF-8 string containing the comment in
+                    "TAG=value" form.
+   \return 0 on success, or a negative value on failure.
+   \retval #OP_EFAULT An internal memory allocation failed.*/
+int opus_tags_add_comment(OpusTags *_tags,const char *_comment)
+ OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+
+/**Replace the binary suffix data at the end of the packet (if any).
+   \param _tags An initialized #OpusTags structure.
+   \param _data A buffer of binary data to append after the encoded user
+                 comments.
+                The least significant bit of the first byte of this data must
+                 be set (to ensure the data is preserved by other editors).
+   \param _len  The number of bytes of binary data to append.
+                This may be zero to remove any existing binary suffix data.
+   \return 0 on success, or a negative value on error.
+   \retval #OP_EINVAL \a _len was negative, or \a _len was positive but
+                       \a _data was <code>NULL</code> or the least significant
+                       bit of the first byte was not set.
+   \retval #OP_EFAULT An internal memory allocation failed.*/
+int opus_tags_set_binary_suffix(OpusTags *_tags,
+ const unsigned char *_data,int _len) OP_ARG_NONNULL(1);
+
+/**Look up a comment value by its tag.
+   \param _tags  An initialized #OpusTags structure.
+   \param _tag   The tag to look up.
+   \param _count The instance of the tag.
+                 The same tag can appear multiple times, each with a distinct
+                  value, so an index is required to retrieve them all.
+                 The order in which these values appear is significant and
+                  should be preserved.
+                 Use opus_tags_query_count() to get the legal range for the
+                  \a _count parameter.
+   \return A pointer to the queried tag's value.
+           This points directly to data in the #OpusTags structure.
+           It should not be modified or freed by the application, and
+            modifications to the structure may invalidate the pointer.
+   \retval NULL If no matching tag is found.*/
+const char *opus_tags_query(const OpusTags *_tags,const char *_tag,int _count)
+ OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+
+/**Look up the number of instances of a tag.
+   Call this first when querying for a specific tag and then iterate over the
+    number of instances with separate calls to opus_tags_query() to retrieve
+    all the values for that tag in order.
+   \param _tags An initialized #OpusTags structure.
+   \param _tag  The tag to look up.
+   \return The number of instances of this particular tag.*/
+int opus_tags_query_count(const OpusTags *_tags,const char *_tag)
+ OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+
+/**Retrieve the binary suffix data at the end of the packet (if any).
+   \param      _tags An initialized #OpusTags structure.
+   \param[out] _len  Returns the number of bytes of binary suffix data returned.
+   \return A pointer to the binary suffix data, or <code>NULL</code> if none
+            was present.*/
+const unsigned char *opus_tags_get_binary_suffix(const OpusTags *_tags,
+ int *_len) OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+
+/**Get the album gain from an R128_ALBUM_GAIN tag, if one was specified.
+   This searches for the first R128_ALBUM_GAIN tag with a valid signed,
+    16-bit decimal integer value and returns the value.
+   This routine is exposed merely for convenience for applications which wish
+    to do something special with the album gain (i.e., display it).
+   If you simply wish to apply the album gain instead of the header gain, you
+    can use op_set_gain_offset() with an #OP_ALBUM_GAIN type and no offset.
+   \param      _tags    An initialized #OpusTags structure.
+   \param[out] _gain_q8 The album gain, in 1/256ths of a dB.
+                        This will lie in the range [-32768,32767], and should
+                         be applied in <em>addition</em> to the header gain.
+                        On error, no value is returned, and the previous
+                         contents remain unchanged.
+   \return 0 on success, or a negative value on error.
+   \retval #OP_FALSE There was no album gain available in the given tags.*/
+int opus_tags_get_album_gain(const OpusTags *_tags,int *_gain_q8)
+ OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+
+/**Get the track gain from an R128_TRACK_GAIN tag, if one was specified.
+   This searches for the first R128_TRACK_GAIN tag with a valid signed,
+    16-bit decimal integer value and returns the value.
+   This routine is exposed merely for convenience for applications which wish
+    to do something special with the track gain (i.e., display it).
+   If you simply wish to apply the track gain instead of the header gain, you
+    can use op_set_gain_offset() with an #OP_TRACK_GAIN type and no offset.
+   \param      _tags    An initialized #OpusTags structure.
+   \param[out] _gain_q8 The track gain, in 1/256ths of a dB.
+                        This will lie in the range [-32768,32767], and should
+                         be applied in <em>addition</em> to the header gain.
+                        On error, no value is returned, and the previous
+                         contents remain unchanged.
+   \return 0 on success, or a negative value on error.
+   \retval #OP_FALSE There was no track gain available in the given tags.*/
+int opus_tags_get_track_gain(const OpusTags *_tags,int *_gain_q8)
+ OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+
+/**Clears the #OpusTags structure.
+   This should be called on an #OpusTags structure after it is no longer
+    needed.
+   It will free all memory used by the structure members.
+   \param _tags The #OpusTags structure to clear.*/
+void opus_tags_clear(OpusTags *_tags) OP_ARG_NONNULL(1);
+
+/**Check if \a _comment is an instance of a \a _tag_name tag.
+   \see opus_tagncompare
+   \param _tag_name A NUL-terminated, case-insensitive, ASCII string containing
+                     the name of the tag to check for (without the terminating
+                     '=' character).
+   \param _comment  The comment string to check.
+   \return An integer less than, equal to, or greater than zero if \a _comment
+            is found respectively, to be less than, to match, or be greater
+            than a "tag=value" string whose tag matches \a _tag_name.*/
+int opus_tagcompare(const char *_tag_name,const char *_comment);
+
+/**Check if \a _comment is an instance of a \a _tag_name tag.
+   This version is slightly more efficient than opus_tagcompare() if the length
+    of the tag name is already known (e.g., because it is a constant).
+   \see opus_tagcompare
+   \param _tag_name A case-insensitive ASCII string containing the name of the
+                     tag to check for (without the terminating '=' character).
+   \param _tag_len  The number of characters in the tag name.
+                    This must be non-negative.
+   \param _comment  The comment string to check.
+   \return An integer less than, equal to, or greater than zero if \a _comment
+            is found respectively, to be less than, to match, or be greater
+            than a "tag=value" string whose tag matches the first \a _tag_len
+            characters of \a _tag_name.*/
+int opus_tagncompare(const char *_tag_name,int _tag_len,const char *_comment);
+
+/**Parse a single METADATA_BLOCK_PICTURE tag.
+   This decodes the BASE64-encoded content of the tag and returns a structure
+    with the MIME type, description, image parameters (if known), and the
+    compressed image data.
+   If the MIME type indicates the presence of an image format we recognize
+    (JPEG, PNG, or GIF) and the actual image data contains the magic signature
+    associated with that format, then the OpusPictureTag::format field will be
+    set to the corresponding format.
+   This is provided as a convenience to avoid requiring applications to parse
+    the MIME type and/or do their own format detection for the commonly used
+    formats.
+   In this case, we also attempt to extract the image parameters directly from
+    the image data (overriding any that were present in the tag, which the
+    specification says applications are not meant to rely on).
+   The application must still provide its own support for actually decoding the
+    image data and, if applicable, retrieving that data from URLs.
+   \param[out] _pic Returns the parsed picture data.
+                    No sanitation is done on the type, MIME type, or
+                     description fields, so these might return invalid values.
+                    The contents of this structure are left unmodified on
+                     failure.
+   \param      _tag The METADATA_BLOCK_PICTURE tag contents.
+                    The leading "METADATA_BLOCK_PICTURE=" portion is optional,
+                     to allow the function to be used on either directly on the
+                     values in OpusTags::user_comments or on the return value
+                     of opus_tags_query().
+   \return 0 on success or a negative value on error.
+   \retval #OP_ENOTFORMAT The METADATA_BLOCK_PICTURE contents were not valid.
+   \retval #OP_EFAULT     There was not enough memory to store the picture tag
+                           contents.*/
+OP_WARN_UNUSED_RESULT int opus_picture_tag_parse(OpusPictureTag *_pic,
+ const char *_tag) OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+
+/**Initializes an #OpusPictureTag structure.
+   This should be called on a freshly allocated #OpusPictureTag structure
+    before attempting to use it.
+   \param _pic The #OpusPictureTag structure to initialize.*/
+void opus_picture_tag_init(OpusPictureTag *_pic) OP_ARG_NONNULL(1);
+
+/**Clears the #OpusPictureTag structure.
+   This should be called on an #OpusPictureTag structure after it is no longer
+    needed.
+   It will free all memory used by the structure members.
+   \param _pic The #OpusPictureTag structure to clear.*/
+void opus_picture_tag_clear(OpusPictureTag *_pic) OP_ARG_NONNULL(1);
+
+/*@}*/
+
+/*@}*/
+
+/**\defgroup url_options URL Reading Options*/
+/*@{*/
+/**\name URL reading options
+   Options for op_url_stream_create() and associated functions.
+   These allow you to provide proxy configuration parameters, skip SSL
+    certificate checks, etc.
+   Options are processed in order, and if the same option is passed multiple
+    times, only the value specified by the last occurrence has an effect
+    (unless otherwise specified).
+   They may be expanded in the future.*/
+/*@{*/
+
+/**@cond PRIVATE*/
+
+/*These are the raw numbers used to define the request codes.
+  They should not be used directly.*/
+#define OP_SSL_SKIP_CERTIFICATE_CHECK_REQUEST (6464)
+#define OP_HTTP_PROXY_HOST_REQUEST            (6528)
+#define OP_HTTP_PROXY_PORT_REQUEST            (6592)
+#define OP_HTTP_PROXY_USER_REQUEST            (6656)
+#define OP_HTTP_PROXY_PASS_REQUEST            (6720)
+#define OP_GET_SERVER_INFO_REQUEST            (6784)
+
+#define OP_URL_OPT(_request) ((_request)+(char *)0)
+
+/*These macros trigger compilation errors or warnings if the wrong types are
+   provided to one of the URL options.*/
+#define OP_CHECK_INT(_x) ((void)((_x)==(opus_int32)0),(opus_int32)(_x))
+#define OP_CHECK_CONST_CHAR_PTR(_x) ((_x)+((_x)-(const char *)(_x)))
+#define OP_CHECK_SERVER_INFO_PTR(_x) ((_x)+((_x)-(OpusServerInfo *)(_x)))
+
+/**@endcond*/
+
+/**HTTP/Shoutcast/Icecast server information associated with a URL.*/
+struct OpusServerInfo{
+  /**The name of the server (icy-name/ice-name).
+     This is <code>NULL</code> if there was no <code>icy-name</code> or
+      <code>ice-name</code> header.*/
+  char        *name;
+  /**A short description of the server (icy-description/ice-description).
+     This is <code>NULL</code> if there was no <code>icy-description</code> or
+      <code>ice-description</code> header.*/
+  char        *description;
+  /**The genre the server falls under (icy-genre/ice-genre).
+     This is <code>NULL</code> if there was no <code>icy-genre</code> or
+      <code>ice-genre</code> header.*/
+  char        *genre;
+  /**The homepage for the server (icy-url/ice-url).
+     This is <code>NULL</code> if there was no <code>icy-url</code> or
+      <code>ice-url</code> header.*/
+  char        *url;
+  /**The software used by the origin server (Server).
+     This is <code>NULL</code> if there was no <code>Server</code> header.*/
+  char        *server;
+  /**The media type of the entity sent to the recepient (Content-Type).
+     This is <code>NULL</code> if there was no <code>Content-Type</code>
+      header.*/
+  char        *content_type;
+  /**The nominal stream bitrate in kbps (icy-br/ice-bitrate).
+     This is <code>-1</code> if there was no <code>icy-br</code> or
+      <code>ice-bitrate</code> header.*/
+  opus_int32   bitrate_kbps;
+  /**Flag indicating whether the server is public (<code>1</code>) or not
+      (<code>0</code>) (icy-pub/ice-public).
+     This is <code>-1</code> if there was no <code>icy-pub</code> or
+      <code>ice-public</code> header.*/
+  int          is_public;
+  /**Flag indicating whether the server is using HTTPS instead of HTTP.
+     This is <code>0</code> unless HTTPS is being used.
+     This may not match the protocol used in the original URL if there were
+      redirections.*/
+  int          is_ssl;
+};
+
+/**Initializes an #OpusServerInfo structure.
+   All fields are set as if the corresponding header was not available.
+   \param _info The #OpusServerInfo structure to initialize.
+   \note If you use this function, you must link against <tt>libopusurl</tt>.*/
+void opus_server_info_init(OpusServerInfo *_info) OP_ARG_NONNULL(1);
+
+/**Clears the #OpusServerInfo structure.
+   This should be called on an #OpusServerInfo structure after it is no longer
+    needed.
+   It will free all memory used by the structure members.
+   \param _info The #OpusServerInfo structure to clear.
+   \note If you use this function, you must link against <tt>libopusurl</tt>.*/
+void opus_server_info_clear(OpusServerInfo *_info) OP_ARG_NONNULL(1);
+
+/**Skip the certificate check when connecting via TLS/SSL (https).
+   \param _b <code>opus_int32</code>: Whether or not to skip the certificate
+              check.
+             The check will be skipped if \a _b is non-zero, and will not be
+              skipped if \a _b is zero.
+   \hideinitializer*/
+#define OP_SSL_SKIP_CERTIFICATE_CHECK(_b) \
+ OP_URL_OPT(OP_SSL_SKIP_CERTIFICATE_CHECK_REQUEST),OP_CHECK_INT(_b)
+
+/**Proxy connections through the given host.
+   If no port is specified via #OP_HTTP_PROXY_PORT, the port number defaults
+    to 8080 (http-alt).
+   All proxy parameters are ignored for non-http and non-https URLs.
+   \param _host <code>const char *</code>: The proxy server hostname.
+                This may be <code>NULL</code> to disable the use of a proxy
+                 server.
+   \hideinitializer*/
+#define OP_HTTP_PROXY_HOST(_host) \
+ OP_URL_OPT(OP_HTTP_PROXY_HOST_REQUEST),OP_CHECK_CONST_CHAR_PTR(_host)
+
+/**Use the given port when proxying connections.
+   This option only has an effect if #OP_HTTP_PROXY_HOST is specified with a
+    non-<code>NULL</code> \a _host.
+   If this option is not provided, the proxy port number defaults to 8080
+    (http-alt).
+   All proxy parameters are ignored for non-http and non-https URLs.
+   \param _port <code>opus_int32</code>: The proxy server port.
+                This must be in the range 0...65535 (inclusive), or the
+                 URL function this is passed to will fail.
+   \hideinitializer*/
+#define OP_HTTP_PROXY_PORT(_port) \
+ OP_URL_OPT(OP_HTTP_PROXY_PORT_REQUEST),OP_CHECK_INT(_port)
+
+/**Use the given user name for authentication when proxying connections.
+   All proxy parameters are ignored for non-http and non-https URLs.
+   \param _user const char *: The proxy server user name.
+                              This may be <code>NULL</code> to disable proxy
+                               authentication.
+                              A non-<code>NULL</code> value only has an effect
+                               if #OP_HTTP_PROXY_HOST and #OP_HTTP_PROXY_PASS
+                               are also specified with non-<code>NULL</code>
+                               arguments.
+   \hideinitializer*/
+#define OP_HTTP_PROXY_USER(_user) \
+ OP_URL_OPT(OP_HTTP_PROXY_USER_REQUEST),OP_CHECK_CONST_CHAR_PTR(_user)
+
+/**Use the given password for authentication when proxying connections.
+   All proxy parameters are ignored for non-http and non-https URLs.
+   \param _pass const char *: The proxy server password.
+                              This may be <code>NULL</code> to disable proxy
+                               authentication.
+                              A non-<code>NULL</code> value only has an effect
+                               if #OP_HTTP_PROXY_HOST and #OP_HTTP_PROXY_USER
+                               are also specified with non-<code>NULL</code>
+                               arguments.
+   \hideinitializer*/
+#define OP_HTTP_PROXY_PASS(_pass) \
+ OP_URL_OPT(OP_HTTP_PROXY_PASS_REQUEST),OP_CHECK_CONST_CHAR_PTR(_pass)
+
+/**Parse information about the streaming server (if any) and return it.
+   Very little validation is done.
+   In particular, OpusServerInfo::url may not be a valid URL,
+    OpusServerInfo::bitrate_kbps may not really be in kbps, and
+    OpusServerInfo::content_type may not be a valid MIME type.
+   The character set of the string fields is not specified anywhere, and should
+    not be assumed to be valid UTF-8.
+   \param _info OpusServerInfo *: Returns information about the server.
+                                  If there is any error opening the stream, the
+                                   contents of this structure remain
+                                   unmodified.
+                                  On success, fills in the structure with the
+                                   server information that was available, if
+                                   any.
+                                  After a successful return, the contents of
+                                   this structure should be freed by calling
+                                   opus_server_info_clear().
+   \hideinitializer*/
+#define OP_GET_SERVER_INFO(_info) \
+ OP_URL_OPT(OP_GET_SERVER_INFO_REQUEST),OP_CHECK_SERVER_INFO_PTR(_info)
+
+/*@}*/
+/*@}*/
+
+/**\defgroup stream_callbacks Abstract Stream Reading Interface*/
+/*@{*/
+/**\name Functions for reading from streams
+   These functions define the interface used to read from and seek in a stream
+    of data.
+   A stream does not need to implement seeking, but the decoder will not be
+    able to seek if it does not do so.
+   These functions also include some convenience routines for working with
+    standard <code>FILE</code> pointers, complete streams stored in a single
+    block of memory, or URLs.*/
+/*@{*/
+
+/**Reads up to \a _nbytes bytes of data from \a _stream.
+   \param      _stream The stream to read from.
+   \param[out] _ptr    The buffer to store the data in.
+   \param      _nbytes The maximum number of bytes to read.
+                       This function may return fewer, though it will not
+                        return zero unless it reaches end-of-file.
+   \return The number of bytes successfully read, or a negative value on
+            error.*/
+typedef int (*op_read_func)(void *_stream,unsigned char *_ptr,int _nbytes);
+
+/**Sets the position indicator for \a _stream.
+   The new position, measured in bytes, is obtained by adding \a _offset
+    bytes to the position specified by \a _whence.
+   If \a _whence is set to <code>SEEK_SET</code>, <code>SEEK_CUR</code>, or
+    <code>SEEK_END</code>, the offset is relative to the start of the stream,
+    the current position indicator, or end-of-file, respectively.
+   \retval 0  Success.
+   \retval -1 Seeking is not supported or an error occurred.
+              <code>errno</code> need not be set.*/
+typedef int (*op_seek_func)(void *_stream,opus_int64 _offset,int _whence);
+
+/**Obtains the current value of the position indicator for \a _stream.
+   \return The current position indicator.*/
+typedef opus_int64 (*op_tell_func)(void *_stream);
+
+/**Closes the underlying stream.
+   \retval 0   Success.
+   \retval EOF An error occurred.
+               <code>errno</code> need not be set.*/
+typedef int (*op_close_func)(void *_stream);
+
+/**The callbacks used to access non-<code>FILE</code> stream resources.
+   The function prototypes are basically the same as for the stdio functions
+    <code>fread()</code>, <code>fseek()</code>, <code>ftell()</code>, and
+    <code>fclose()</code>.
+   The differences are that the <code>FILE *</code> arguments have been
+    replaced with a <code>void *</code>, which is to be used as a pointer to
+    whatever internal data these functions might need, that #seek and #tell
+    take and return 64-bit offsets, and that #seek <em>must</em> return -1 if
+    the stream is unseekable.*/
+struct OpusFileCallbacks{
+  /**Used to read data from the stream.
+     This must not be <code>NULL</code>.*/
+  op_read_func  read;
+  /**Used to seek in the stream.
+     This may be <code>NULL</code> if seeking is not implemented.*/
+  op_seek_func  seek;
+  /**Used to return the current read position in the stream.
+     This may be <code>NULL</code> if seeking is not implemented.*/
+  op_tell_func  tell;
+  /**Used to close the stream when the decoder is freed.
+     This may be <code>NULL</code> to leave the stream open.*/
+  op_close_func close;
+};
+
+/**Opens a stream with <code>fopen()</code> and fills in a set of callbacks
+    that can be used to access it.
+   This is useful to avoid writing your own portable 64-bit seeking wrappers,
+    and also avoids cross-module linking issues on Windows, where a
+    <code>FILE *</code> must be accessed by routines defined in the same module
+    that opened it.
+   \param[out] _cb   The callbacks to use for this file.
+                     If there is an error opening the file, nothing will be
+                      filled in here.
+   \param      _path The path to the file to open.
+                     On Windows, this string must be UTF-8 (to allow access to
+                      files whose names cannot be represented in the current
+                      MBCS code page).
+                     All other systems use the native character encoding.
+   \param      _mode The mode to open the file in.
+   \return A stream handle to use with the callbacks, or <code>NULL</code> on
+            error.*/
+OP_WARN_UNUSED_RESULT void *op_fopen(OpusFileCallbacks *_cb,
+ const char *_path,const char *_mode) OP_ARG_NONNULL(1) OP_ARG_NONNULL(2)
+ OP_ARG_NONNULL(3);
+
+/**Opens a stream with <code>fdopen()</code> and fills in a set of callbacks
+    that can be used to access it.
+   This is useful to avoid writing your own portable 64-bit seeking wrappers,
+    and also avoids cross-module linking issues on Windows, where a
+    <code>FILE *</code> must be accessed by routines defined in the same module
+    that opened it.
+   \param[out] _cb   The callbacks to use for this file.
+                     If there is an error opening the file, nothing will be
+                      filled in here.
+   \param      _fd   The file descriptor to open.
+   \param      _mode The mode to open the file in.
+   \return A stream handle to use with the callbacks, or <code>NULL</code> on
+            error.*/
+OP_WARN_UNUSED_RESULT void *op_fdopen(OpusFileCallbacks *_cb,
+ int _fd,const char *_mode) OP_ARG_NONNULL(1) OP_ARG_NONNULL(3);
+
+/**Opens a stream with <code>freopen()</code> and fills in a set of callbacks
+    that can be used to access it.
+   This is useful to avoid writing your own portable 64-bit seeking wrappers,
+    and also avoids cross-module linking issues on Windows, where a
+    <code>FILE *</code> must be accessed by routines defined in the same module
+    that opened it.
+   \param[out] _cb     The callbacks to use for this file.
+                       If there is an error opening the file, nothing will be
+                        filled in here.
+   \param      _path   The path to the file to open.
+                       On Windows, this string must be UTF-8 (to allow access
+                        to files whose names cannot be represented in the
+                        current MBCS code page).
+                       All other systems use the native character encoding.
+   \param      _mode   The mode to open the file in.
+   \param      _stream A stream previously returned by op_fopen(), op_fdopen(),
+                        or op_freopen().
+   \return A stream handle to use with the callbacks, or <code>NULL</code> on
+            error.*/
+OP_WARN_UNUSED_RESULT void *op_freopen(OpusFileCallbacks *_cb,
+ const char *_path,const char *_mode,void *_stream) OP_ARG_NONNULL(1)
+ OP_ARG_NONNULL(2) OP_ARG_NONNULL(3) OP_ARG_NONNULL(4);
+
+/**Creates a stream that reads from the given block of memory.
+   This block of memory must contain the complete stream to decode.
+   This is useful for caching small streams (e.g., sound effects) in RAM.
+   \param[out] _cb   The callbacks to use for this stream.
+                     If there is an error creating the stream, nothing will be
+                      filled in here.
+   \param      _data The block of memory to read from.
+   \param      _size The size of the block of memory.
+   \return A stream handle to use with the callbacks, or <code>NULL</code> on
+            error.*/
+OP_WARN_UNUSED_RESULT void *op_mem_stream_create(OpusFileCallbacks *_cb,
+ const unsigned char *_data,size_t _size) OP_ARG_NONNULL(1);
+
+/**Creates a stream that reads from the given URL.
+   This function behaves identically to op_url_stream_create(), except that it
+    takes a va_list instead of a variable number of arguments.
+   It does not call the <code>va_end</code> macro, and because it invokes the
+    <code>va_arg</code> macro, the value of \a _ap is undefined after the call.
+   \note If you use this function, you must link against <tt>libopusurl</tt>.
+   \param[out]    _cb  The callbacks to use for this stream.
+                       If there is an error creating the stream, nothing will
+                        be filled in here.
+   \param         _url The URL to read from.
+                       Currently only the <file:>, <http:>, and <https:>
+                        schemes are supported.
+                       Both <http:> and <https:> may be disabled at compile
+                        time, in which case opening such URLs will always fail.
+                       Currently this only supports URIs.
+                       IRIs should be converted to UTF-8 and URL-escaped, with
+                        internationalized domain names encoded in punycode,
+                        before passing them to this function.
+   \param[in,out] _ap  A list of the \ref url_options "optional flags" to use.
+                       This is a variable-length list of options terminated
+                        with <code>NULL</code>.
+   \return A stream handle to use with the callbacks, or <code>NULL</code> on
+            error.*/
+OP_WARN_UNUSED_RESULT void *op_url_stream_vcreate(OpusFileCallbacks *_cb,
+ const char *_url,va_list _ap) OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+
+/**Creates a stream that reads from the given URL.
+   \note If you use this function, you must link against <tt>libopusurl</tt>.
+   \param[out] _cb  The callbacks to use for this stream.
+                    If there is an error creating the stream, nothing will be
+                     filled in here.
+   \param      _url The URL to read from.
+                    Currently only the <file:>, <http:>, and <https:> schemes
+                     are supported.
+                    Both <http:> and <https:> may be disabled at compile time,
+                     in which case opening such URLs will always fail.
+                    Currently this only supports URIs.
+                    IRIs should be converted to UTF-8 and URL-escaped, with
+                     internationalized domain names encoded in punycode, before
+                     passing them to this function.
+   \param      ...  The \ref url_options "optional flags" to use.
+                    This is a variable-length list of options terminated with
+                     <code>NULL</code>.
+   \return A stream handle to use with the callbacks, or <code>NULL</code> on
+            error.*/
+OP_WARN_UNUSED_RESULT void *op_url_stream_create(OpusFileCallbacks *_cb,
+ const char *_url,...) OP_ARG_NONNULL(1) OP_ARG_NONNULL(2);
+
+/*@}*/
+/*@}*/
+
+/**\defgroup stream_open_close Opening and Closing*/
+/*@{*/
+/**\name Functions for opening and closing streams
+
+   These functions allow you to test a stream to see if it is Opus, open it,
+    and close it.
+   Several flavors are provided for each of the built-in stream types, plus a
+    more general version which takes a set of application-provided callbacks.*/
+/*@{*/
+
+/**Test to see if this is an Opus stream.
+   For good results, you will need at least 57 bytes (for a pure Opus-only
+    stream).
+   Something like 512 bytes will give more reliable results for multiplexed
+    streams.
+   This function is meant to be a quick-rejection filter.
+   Its purpose is not to guarantee that a stream is a valid Opus stream, but to
+    ensure that it looks enough like Opus that it isn't going to be recognized
+    as some other format (except possibly an Opus stream that is also
+    multiplexed with other codecs, such as video).
+   \param[out] _head     The parsed ID header contents.
+                         You may pass <code>NULL</code> if you do not need
+                          this information.
+                         If the function fails, the contents of this structure
+                          remain untouched.
+   \param _initial_data  An initial buffer of data from the start of the
+                          stream.
+   \param _initial_bytes The number of bytes in \a _initial_data.
+   \return 0 if the data appears to be Opus, or a negative value on error.
+   \retval #OP_FALSE      There was not enough data to tell if this was an Opus
+                           stream or not.
+   \retval #OP_EFAULT     An internal memory allocation failed.
+   \retval #OP_EIMPL      The stream used a feature that is not implemented,
+                           such as an unsupported channel family.
+   \retval #OP_ENOTFORMAT If the data did not contain a recognizable ID
+                           header for an Opus stream.
+   \retval #OP_EVERSION   If the version field signaled a version this library
+                           does not know how to parse.
+   \retval #OP_EBADHEADER The ID header was not properly formatted or contained
+                           illegal values.*/
+int op_test(OpusHead *_head,
+ const unsigned char *_initial_data,size_t _initial_bytes);
+
+/**Open a stream from the given file path.
+   \param      _path  The path to the file to open.
+   \param[out] _error Returns 0 on success, or a failure code on error.
+                      You may pass in <code>NULL</code> if you don't want the
+                       failure code.
+                      The failure code will be #OP_EFAULT if the file could not
+                       be opened, or one of the other failure codes from
+                       op_open_callbacks() otherwise.
+   \return A freshly opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_open_file(const char *_path,int *_error)
+ OP_ARG_NONNULL(1);
+
+/**Open a stream from a memory buffer.
+   \param      _data  The memory buffer to open.
+   \param      _size  The number of bytes in the buffer.
+   \param[out] _error Returns 0 on success, or a failure code on error.
+                      You may pass in <code>NULL</code> if you don't want the
+                       failure code.
+                      See op_open_callbacks() for a full list of failure codes.
+   \return A freshly opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_open_memory(const unsigned char *_data,
+ size_t _size,int *_error);
+
+/**Open a stream from a URL.
+   This function behaves identically to op_open_url(), except that it
+    takes a va_list instead of a variable number of arguments.
+   It does not call the <code>va_end</code> macro, and because it invokes the
+    <code>va_arg</code> macro, the value of \a _ap is undefined after the call.
+   \note If you use this function, you must link against <tt>libopusurl</tt>.
+   \param         _url   The URL to open.
+                         Currently only the <file:>, <http:>, and <https:>
+                          schemes are supported.
+                         Both <http:> and <https:> may be disabled at compile
+                          time, in which case opening such URLs will always
+                          fail.
+                         Currently this only supports URIs.
+                         IRIs should be converted to UTF-8 and URL-escaped,
+                          with internationalized domain names encoded in
+                          punycode, before passing them to this function.
+   \param[out]    _error Returns 0 on success, or a failure code on error.
+                         You may pass in <code>NULL</code> if you don't want
+                          the failure code.
+                         See op_open_callbacks() for a full list of failure
+                          codes.
+   \param[in,out] _ap    A list of the \ref url_options "optional flags" to
+                          use.
+                         This is a variable-length list of options terminated
+                          with <code>NULL</code>.
+   \return A freshly opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_vopen_url(const char *_url,
+ int *_error,va_list _ap) OP_ARG_NONNULL(1);
+
+/**Open a stream from a URL.
+   \note If you use this function, you must link against <tt>libopusurl</tt>.
+   \param      _url   The URL to open.
+                      Currently only the <file:>, <http:>, and <https:> schemes
+                       are supported.
+                      Both <http:> and <https:> may be disabled at compile
+                       time, in which case opening such URLs will always fail.
+                      Currently this only supports URIs.
+                      IRIs should be converted to UTF-8 and URL-escaped, with
+                       internationalized domain names encoded in punycode,
+                       before passing them to this function.
+   \param[out] _error Returns 0 on success, or a failure code on error.
+                      You may pass in <code>NULL</code> if you don't want the
+                       failure code.
+                      See op_open_callbacks() for a full list of failure codes.
+   \param      ...    The \ref url_options "optional flags" to use.
+                      This is a variable-length list of options terminated with
+                       <code>NULL</code>.
+   \return A freshly opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_open_url(const char *_url,
+ int *_error,...) OP_ARG_NONNULL(1);
+
+/**Open a stream using the given set of callbacks to access it.
+   \param _stream        The stream to read from (e.g., a <code>FILE *</code>).
+                         This value will be passed verbatim as the first
+                          argument to all of the callbacks.
+   \param _cb            The callbacks with which to access the stream.
+                         <code><a href="#op_read_func">read()</a></code> must
+                          be implemented.
+                         <code><a href="#op_seek_func">seek()</a></code> and
+                          <code><a href="#op_tell_func">tell()</a></code> may
+                          be <code>NULL</code>, or may always return -1 to
+                          indicate a stream is unseekable, but if
+                          <code><a href="#op_seek_func">seek()</a></code> is
+                          implemented and succeeds on a particular stream, then
+                          <code><a href="#op_tell_func">tell()</a></code> must
+                          also.
+                         <code><a href="#op_close_func">close()</a></code> may
+                          be <code>NULL</code>, but if it is not, it will be
+                          called when the \c OggOpusFile is destroyed by
+                          op_free().
+                         It will not be called if op_open_callbacks() fails
+                          with an error.
+   \param _initial_data  An initial buffer of data from the start of the
+                          stream.
+                         Applications can read some number of bytes from the
+                          start of the stream to help identify this as an Opus
+                          stream, and then provide them here to allow the
+                          stream to be opened, even if it is unseekable.
+   \param _initial_bytes The number of bytes in \a _initial_data.
+                         If the stream is seekable, its current position (as
+                          reported by
+                          <code><a href="#opus_tell_func">tell()</a></code>
+                          at the start of this function) must be equal to
+                          \a _initial_bytes.
+                         Otherwise, seeking to absolute positions will
+                          generate inconsistent results.
+   \param[out] _error    Returns 0 on success, or a failure code on error.
+                         You may pass in <code>NULL</code> if you don't want
+                          the failure code.
+                         The failure code will be one of
+                         <dl>
+                           <dt>#OP_EREAD</dt>
+                           <dd>An underlying read, seek, or tell operation
+                            failed when it should have succeeded, or we failed
+                            to find data in the stream we had seen before.</dd>
+                           <dt>#OP_EFAULT</dt>
+                           <dd>There was a memory allocation failure, or an
+                            internal library error.</dd>
+                           <dt>#OP_EIMPL</dt>
+                           <dd>The stream used a feature that is not
+                            implemented, such as an unsupported channel
+                            family.</dd>
+                           <dt>#OP_EINVAL</dt>
+                           <dd><code><a href="#op_seek_func">seek()</a></code>
+                            was implemented and succeeded on this source, but
+                            <code><a href="#op_tell_func">tell()</a></code>
+                            did not, or the starting position indicator was
+                            not equal to \a _initial_bytes.</dd>
+                           <dt>#OP_ENOTFORMAT</dt>
+                           <dd>The stream contained a link that did not have
+                            any logical Opus streams in it.</dd>
+                           <dt>#OP_EBADHEADER</dt>
+                           <dd>A required header packet was not properly
+                            formatted, contained illegal values, or was missing
+                            altogether.</dd>
+                           <dt>#OP_EVERSION</dt>
+                           <dd>An ID header contained an unrecognized version
+                            number.</dd>
+                           <dt>#OP_EBADLINK</dt>
+                           <dd>We failed to find data we had seen before after
+                            seeking.</dd>
+                           <dt>#OP_EBADTIMESTAMP</dt>
+                           <dd>The first or last timestamp in a link failed
+                            basic validity checks.</dd>
+                         </dl>
+   \return A freshly opened \c OggOpusFile, or <code>NULL</code> on error.
+           <tt>libopusfile</tt> does <em>not</em> take ownership of the stream
+            if the call fails.
+           The calling application is responsible for closing the stream if
+            this call returns an error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_open_callbacks(void *_stream,
+ const OpusFileCallbacks *_cb,const unsigned char *_initial_data,
+ size_t _initial_bytes,int *_error) OP_ARG_NONNULL(2);
+
+/**Partially open a stream from the given file path.
+   \see op_test_callbacks
+   \param      _path  The path to the file to open.
+   \param[out] _error Returns 0 on success, or a failure code on error.
+                      You may pass in <code>NULL</code> if you don't want the
+                       failure code.
+                      The failure code will be #OP_EFAULT if the file could not
+                       be opened, or one of the other failure codes from
+                       op_open_callbacks() otherwise.
+   \return A partially opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_test_file(const char *_path,int *_error)
+ OP_ARG_NONNULL(1);
+
+/**Partially open a stream from a memory buffer.
+   \see op_test_callbacks
+   \param      _data  The memory buffer to open.
+   \param      _size  The number of bytes in the buffer.
+   \param[out] _error Returns 0 on success, or a failure code on error.
+                      You may pass in <code>NULL</code> if you don't want the
+                       failure code.
+                      See op_open_callbacks() for a full list of failure codes.
+   \return A partially opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_test_memory(const unsigned char *_data,
+ size_t _size,int *_error);
+
+/**Partially open a stream from a URL.
+   This function behaves identically to op_test_url(), except that it
+    takes a va_list instead of a variable number of arguments.
+   It does not call the <code>va_end</code> macro, and because it invokes the
+    <code>va_arg</code> macro, the value of \a _ap is undefined after the call.
+   \note If you use this function, you must link against <tt>libopusurl</tt>.
+   \see op_test_url
+   \see op_test_callbacks
+   \param         _url    The URL to open.
+                          Currently only the <file:>, <http:>, and <https:>
+                           schemes are supported.
+                          Both <http:> and <https:> may be disabled at compile
+                           time, in which case opening such URLs will always
+                           fail.
+                          Currently this only supports URIs.
+                          IRIs should be converted to UTF-8 and URL-escaped,
+                           with internationalized domain names encoded in
+                           punycode, before passing them to this function.
+   \param[out]    _error  Returns 0 on success, or a failure code on error.
+                          You may pass in <code>NULL</code> if you don't want
+                           the failure code.
+                          See op_open_callbacks() for a full list of failure
+                           codes.
+   \param[in,out] _ap     A list of the \ref url_options "optional flags" to
+                           use.
+                          This is a variable-length list of options terminated
+                           with <code>NULL</code>.
+   \return A partially opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_vtest_url(const char *_url,
+ int *_error,va_list _ap) OP_ARG_NONNULL(1);
+
+/**Partially open a stream from a URL.
+   \note If you use this function, you must link against <tt>libopusurl</tt>.
+   \see op_test_callbacks
+   \param      _url    The URL to open.
+                       Currently only the <file:>, <http:>, and <https:>
+                        schemes are supported.
+                       Both <http:> and <https:> may be disabled at compile
+                        time, in which case opening such URLs will always fail.
+                       Currently this only supports URIs.
+                       IRIs should be converted to UTF-8 and URL-escaped, with
+                        internationalized domain names encoded in punycode,
+                        before passing them to this function.
+   \param[out] _error  Returns 0 on success, or a failure code on error.
+                       You may pass in <code>NULL</code> if you don't want the
+                        failure code.
+                       See op_open_callbacks() for a full list of failure
+                        codes.
+   \param      ...     The \ref url_options "optional flags" to use.
+                       This is a variable-length list of options terminated
+                        with <code>NULL</code>.
+   \return A partially opened \c OggOpusFile, or <code>NULL</code> on error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_test_url(const char *_url,
+ int *_error,...) OP_ARG_NONNULL(1);
+
+/**Partially open a stream using the given set of callbacks to access it.
+   This tests for Opusness and loads the headers for the first link.
+   It does not seek (although it tests for seekability).
+   You can query a partially open stream for the few pieces of basic
+    information returned by op_serialno(), op_channel_count(), op_head(), and
+    op_tags() (but only for the first link).
+   You may also determine if it is seekable via a call to op_seekable().
+   You cannot read audio from the stream, seek, get the size or duration,
+    get information from links other than the first one, or even get the total
+    number of links until you finish opening the stream with op_test_open().
+   If you do not need to do any of these things, you can dispose of it with
+    op_free() instead.
+
+   This function is provided mostly to simplify porting existing code that used
+    <tt>libvorbisfile</tt>.
+   For new code, you are likely better off using op_test() instead, which
+    is less resource-intensive, requires less data to succeed, and imposes a
+    hard limit on the amount of data it examines (important for unseekable
+    streams, where all such data must be buffered until you are sure of the
+    stream type).
+   \param _stream        The stream to read from (e.g., a <code>FILE *</code>).
+                         This value will be passed verbatim as the first
+                          argument to all of the callbacks.
+   \param _cb            The callbacks with which to access the stream.
+                         <code><a href="#op_read_func">read()</a></code> must
+                          be implemented.
+                         <code><a href="#op_seek_func">seek()</a></code> and
+                          <code><a href="#op_tell_func">tell()</a></code> may
+                          be <code>NULL</code>, or may always return -1 to
+                          indicate a stream is unseekable, but if
+                          <code><a href="#op_seek_func">seek()</a></code> is
+                          implemented and succeeds on a particular stream, then
+                          <code><a href="#op_tell_func">tell()</a></code> must
+                          also.
+                         <code><a href="#op_close_func">close()</a></code> may
+                          be <code>NULL</code>, but if it is not, it will be
+                          called when the \c OggOpusFile is destroyed by
+                          op_free().
+                         It will not be called if op_open_callbacks() fails
+                          with an error.
+   \param _initial_data  An initial buffer of data from the start of the
+                          stream.
+                         Applications can read some number of bytes from the
+                          start of the stream to help identify this as an Opus
+                          stream, and then provide them here to allow the
+                          stream to be tested more thoroughly, even if it is
+                          unseekable.
+   \param _initial_bytes The number of bytes in \a _initial_data.
+                         If the stream is seekable, its current position (as
+                          reported by
+                          <code><a href="#opus_tell_func">tell()</a></code>
+                          at the start of this function) must be equal to
+                          \a _initial_bytes.
+                         Otherwise, seeking to absolute positions will
+                          generate inconsistent results.
+   \param[out] _error    Returns 0 on success, or a failure code on error.
+                         You may pass in <code>NULL</code> if you don't want
+                          the failure code.
+                         See op_open_callbacks() for a full list of failure
+                          codes.
+   \return A partially opened \c OggOpusFile, or <code>NULL</code> on error.
+           <tt>libopusfile</tt> does <em>not</em> take ownership of the stream
+            if the call fails.
+           The calling application is responsible for closing the stream if
+            this call returns an error.*/
+OP_WARN_UNUSED_RESULT OggOpusFile *op_test_callbacks(void *_stream,
+ const OpusFileCallbacks *_cb,const unsigned char *_initial_data,
+ size_t _initial_bytes,int *_error) OP_ARG_NONNULL(2);
+
+/**Finish opening a stream partially opened with op_test_callbacks() or one of
+    the associated convenience functions.
+   If this function fails, you are still responsible for freeing the
+    \c OggOpusFile with op_free().
+   \param _of The \c OggOpusFile to finish opening.
+   \return 0 on success, or a negative value on error.
+   \retval #OP_EREAD         An underlying read, seek, or tell operation failed
+                              when it should have succeeded.
+   \retval #OP_EFAULT        There was a memory allocation failure, or an
+                              internal library error.
+   \retval #OP_EIMPL         The stream used a feature that is not implemented,
+                              such as an unsupported channel family.
+   \retval #OP_EINVAL        The stream was not partially opened with
+                              op_test_callbacks() or one of the associated
+                              convenience functions.
+   \retval #OP_ENOTFORMAT    The stream contained a link that did not have any
+                              logical Opus streams in it.
+   \retval #OP_EBADHEADER    A required header packet was not properly
+                              formatted, contained illegal values, or was
+                              missing altogether.
+   \retval #OP_EVERSION      An ID header contained an unrecognized version
+                              number.
+   \retval #OP_EBADLINK      We failed to find data we had seen before after
+                              seeking.
+   \retval #OP_EBADTIMESTAMP The first or last timestamp in a link failed basic
+                              validity checks.*/
+int op_test_open(OggOpusFile *_of) OP_ARG_NONNULL(1);
+
+/**Release all memory used by an \c OggOpusFile.
+   \param _of The \c OggOpusFile to free.*/
+void op_free(OggOpusFile *_of);
+
+/*@}*/
+/*@}*/
+
+/**\defgroup stream_info Stream Information*/
+/*@{*/
+/**\name Functions for obtaining information about streams
+
+   These functions allow you to get basic information about a stream, including
+    seekability, the number of links (for chained streams), plus the size,
+    duration, bitrate, header parameters, and meta information for each link
+    (or, where available, the stream as a whole).
+   Some of these (size, duration) are only available for seekable streams.
+   You can also query the current stream position, link, and playback time,
+    and instantaneous bitrate during playback.
+
+   Some of these functions may be used successfully on the partially open
+    streams returned by op_test_callbacks() or one of the associated
+    convenience functions.
+   Their documention will indicate so explicitly.*/
+/*@{*/
+
+/**Returns whether or not the stream being read is seekable.
+   This is true if
+   <ol>
+   <li>The <code><a href="#op_seek_func">seek()</a></code> and
+    <code><a href="#op_tell_func">tell()</a></code> callbacks are both
+    non-<code>NULL</code>,</li>
+   <li>The <code><a href="#op_seek_func">seek()</a></code> callback was
+    successfully executed at least once, and</li>
+   <li>The <code><a href="#op_tell_func">tell()</a></code> callback was
+    successfully able to report the position indicator afterwards.</li>
+   </ol>
+   This function may be called on partially-opened streams.
+   \param _of The \c OggOpusFile whose seekable status is to be returned.
+   \return A non-zero value if seekable, and 0 if unseekable.*/
+int op_seekable(const OggOpusFile *_of) OP_ARG_NONNULL(1);
+
+/**Returns the number of links in this chained stream.
+   This function may be called on partially-opened streams, but it will always
+    return 1.
+   The actual number of links is not known until the stream is fully opened.
+   \param _of The \c OggOpusFile from which to retrieve the link count.
+   \return For fully-open seekable streams, this returns the total number of
+            links in the whole stream, which will be at least 1.
+           For partially-open or unseekable streams, this always returns 1.*/
+int op_link_count(const OggOpusFile *_of) OP_ARG_NONNULL(1);
+
+/**Get the serial number of the given link in a (possibly-chained) Ogg Opus
+    stream.
+   This function may be called on partially-opened streams, but it will always
+    return the serial number of the Opus stream in the first link.
+   \param _of The \c OggOpusFile from which to retrieve the serial number.
+   \param _li The index of the link whose serial number should be retrieved.
+              Use a negative number to get the serial number of the current
+               link.
+   \return The serial number of the given link.
+           If \a _li is greater than the total number of links, this returns
+            the serial number of the last link.
+           If the stream is not seekable, this always returns the serial number
+            of the current link.*/
+opus_uint32 op_serialno(const OggOpusFile *_of,int _li) OP_ARG_NONNULL(1);
+
+/**Get the channel count of the given link in a (possibly-chained) Ogg Opus
+    stream.
+   This is equivalent to <code>op_head(_of,_li)->channel_count</code>, but
+    is provided for convenience.
+   This function may be called on partially-opened streams, but it will always
+    return the channel count of the Opus stream in the first link.
+   \param _of The \c OggOpusFile from which to retrieve the channel count.
+   \param _li The index of the link whose channel count should be retrieved.
+              Use a negative number to get the channel count of the current
+               link.
+   \return The channel count of the given link.
+           If \a _li is greater than the total number of links, this returns
+            the channel count of the last link.
+           If the stream is not seekable, this always returns the channel count
+            of the current link.*/
+int op_channel_count(const OggOpusFile *_of,int _li) OP_ARG_NONNULL(1);
+
+/**Get the total (compressed) size of the stream, or of an individual link in
+    a (possibly-chained) Ogg Opus stream, including all headers and Ogg muxing
+    overhead.
+   \warning If the Opus stream (or link) is concurrently multiplexed with other
+    logical streams (e.g., video), this returns the size of the entire stream
+    (or link), not just the number of bytes in the first logical Opus stream.
+   Returning the latter would require scanning the entire file.
+   \param _of The \c OggOpusFile from which to retrieve the compressed size.
+   \param _li The index of the link whose compressed size should be computed.
+              Use a negative number to get the compressed size of the entire
+               stream.
+   \return The compressed size of the entire stream if \a _li is negative, the
+            compressed size of link \a _li if it is non-negative, or a negative
+            value on error.
+           The compressed size of the entire stream may be smaller than that
+            of the underlying stream if trailing garbage was detected in the
+            file.
+   \retval #OP_EINVAL The stream is not seekable (so we can't know the length),
+                       \a _li wasn't less than the total number of links in
+                       the stream, or the stream was only partially open.*/
+opus_int64 op_raw_total(const OggOpusFile *_of,int _li) OP_ARG_NONNULL(1);
+
+/**Get the total PCM length (number of samples at 48 kHz) of the stream, or of
+    an individual link in a (possibly-chained) Ogg Opus stream.
+   Users looking for <code>op_time_total()</code> should use op_pcm_total()
+    instead.
+   Because timestamps in Opus are fixed at 48 kHz, there is no need for a
+    separate function to convert this to seconds (and leaving it out avoids
+    introducing floating point to the API, for those that wish to avoid it).
+   \param _of The \c OggOpusFile from which to retrieve the PCM offset.
+   \param _li The index of the link whose PCM length should be computed.
+              Use a negative number to get the PCM length of the entire stream.
+   \return The PCM length of the entire stream if \a _li is negative, the PCM
+            length of link \a _li if it is non-negative, or a negative value on
+            error.
+   \retval #OP_EINVAL The stream is not seekable (so we can't know the length),
+                       \a _li wasn't less than the total number of links in
+                       the stream, or the stream was only partially open.*/
+ogg_int64_t op_pcm_total(const OggOpusFile *_of,int _li) OP_ARG_NONNULL(1);
+
+/**Get the ID header information for the given link in a (possibly chained) Ogg
+    Opus stream.
+   This function may be called on partially-opened streams, but it will always
+    return the ID header information of the Opus stream in the first link.
+   \param _of The \c OggOpusFile from which to retrieve the ID header
+               information.
+   \param _li The index of the link whose ID header information should be
+               retrieved.
+              Use a negative number to get the ID header information of the
+               current link.
+              For an unseekable stream, \a _li is ignored, and the ID header
+               information for the current link is always returned, if
+               available.
+   \return The contents of the ID header for the given link.*/
+const OpusHead *op_head(const OggOpusFile *_of,int _li) OP_ARG_NONNULL(1);
+
+/**Get the comment header information for the given link in a (possibly
+    chained) Ogg Opus stream.
+   This function may be called on partially-opened streams, but it will always
+    return the tags from the Opus stream in the first link.
+   \param _of The \c OggOpusFile from which to retrieve the comment header
+               information.
+   \param _li The index of the link whose comment header information should be
+               retrieved.
+              Use a negative number to get the comment header information of
+               the current link.
+              For an unseekable stream, \a _li is ignored, and the comment
+               header information for the current link is always returned, if
+               available.
+   \return The contents of the comment header for the given link, or
+            <code>NULL</code> if this is an unseekable stream that encountered
+            an invalid link.*/
+const OpusTags *op_tags(const OggOpusFile *_of,int _li) OP_ARG_NONNULL(1);
+
+/**Retrieve the index of the current link.
+   This is the link that produced the data most recently read by
+    op_read_float() or its associated functions, or, after a seek, the link
+    that the seek target landed in.
+   Reading more data may advance the link index (even on the first read after a
+    seek).
+   \param _of The \c OggOpusFile from which to retrieve the current link index.
+   \return The index of the current link on success, or a negative value on
+            failure.
+           For seekable streams, this is a number between 0 (inclusive) and the
+            value returned by op_link_count() (exclusive).
+           For unseekable streams, this value starts at 0 and increments by one
+            each time a new link is encountered (even though op_link_count()
+            always returns 1).
+   \retval #OP_EINVAL The stream was only partially open.*/
+int op_current_link(const OggOpusFile *_of) OP_ARG_NONNULL(1);
+
+/**Computes the bitrate of the stream, or of an individual link in a
+    (possibly-chained) Ogg Opus stream.
+   The stream must be seekable to compute the bitrate.
+   For unseekable streams, use op_bitrate_instant() to get periodic estimates.
+   \warning If the Opus stream (or link) is concurrently multiplexed with other
+    logical streams (e.g., video), this uses the size of the entire stream (or
+    link) to compute the bitrate, not just the number of bytes in the first
+    logical Opus stream.
+   Returning the latter requires scanning the entire file, but this may be done
+    by decoding the whole file and calling op_bitrate_instant() once at the
+    end.
+   Install a trivial decoding callback with op_set_decode_callback() if you
+    wish to skip actual decoding during this process.
+   \param _of The \c OggOpusFile from which to retrieve the bitrate.
+   \param _li The index of the link whose bitrate should be computed.
+              Use a negative number to get the bitrate of the whole stream.
+   \return The bitrate on success, or a negative value on error.
+   \retval #OP_EINVAL The stream was only partially open, the stream was not
+                       seekable, or \a _li was larger than the number of
+                       links.*/
+opus_int32 op_bitrate(const OggOpusFile *_of,int _li) OP_ARG_NONNULL(1);
+
+/**Compute the instantaneous bitrate, measured as the ratio of bits to playable
+    samples decoded since a) the last call to op_bitrate_instant(), b) the last
+    seek, or c) the start of playback, whichever was most recent.
+   This will spike somewhat after a seek or at the start/end of a chain
+    boundary, as pre-skip, pre-roll, and end-trimming causes samples to be
+    decoded but not played.
+   \param _of The \c OggOpusFile from which to retrieve the bitrate.
+   \return The bitrate, in bits per second, or a negative value on error.
+   \retval #OP_FALSE  No data has been decoded since any of the events
+                       described above.
+   \retval #OP_EINVAL The stream was only partially open.*/
+opus_int32 op_bitrate_instant(OggOpusFile *_of) OP_ARG_NONNULL(1);
+
+/**Obtain the current value of the position indicator for \a _of.
+   \param _of The \c OggOpusFile from which to retrieve the position indicator.
+   \return The byte position that is currently being read from.
+   \retval #OP_EINVAL The stream was only partially open.*/
+opus_int64 op_raw_tell(const OggOpusFile *_of) OP_ARG_NONNULL(1);
+
+/**Obtain the PCM offset of the next sample to be read.
+   If the stream is not properly timestamped, this might not increment by the
+    proper amount between reads, or even return monotonically increasing
+    values.
+   \param _of The \c OggOpusFile from which to retrieve the PCM offset.
+   \return The PCM offset of the next sample to be read.
+   \retval #OP_EINVAL The stream was only partially open.*/
+ogg_int64_t op_pcm_tell(const OggOpusFile *_of) OP_ARG_NONNULL(1);
+
+/*@}*/
+/*@}*/
+
+/**\defgroup stream_seeking Seeking*/
+/*@{*/
+/**\name Functions for seeking in Opus streams
+
+   These functions let you seek in Opus streams, if the underlying stream
+    support it.
+   Seeking is implemented for all built-in stream I/O routines, though some
+    individual streams may not be seekable (pipes, live HTTP streams, or HTTP
+    streams from a server that does not support <code>Range</code> requests).
+
+   op_raw_seek() is the fastest: it is guaranteed to perform at most one
+    physical seek, but, since the target is a byte position, makes no guarantee
+    how close to a given time it will come.
+   op_pcm_seek() provides sample-accurate seeking.
+   The number of physical seeks it requires is still quite small (often 1 or
+    2, even in highly variable bitrate streams).
+
+   Seeking in Opus requires decoding some pre-roll amount before playback to
+    allow the internal state to converge (as if recovering from packet loss).
+   This is handled internally by <tt>libopusfile</tt>, but means there is
+    little extra overhead for decoding up to the exact position requested
+    (since it must decode some amount of audio anyway).
+   It also means that decoding after seeking may not return exactly the same
+    values as would be obtained by decoding the stream straight through.
+   However, such differences are expected to be smaller than the loss
+    introduced by Opus's lossy compression.*/
+/*@{*/
+
+/**Seek to a byte offset relative to the <b>compressed</b> data.
+   This also scans packets to update the PCM cursor.
+   It will cross a logical bitstream boundary, but only if it can't get any
+    packets out of the tail of the link to which it seeks.
+   \param _of          The \c OggOpusFile in which to seek.
+   \param _byte_offset The byte position to seek to.
+                       This must be between 0 and #op_raw_total(\a _of,\c -1)
+                        (inclusive).
+   \return 0 on success, or a negative error code on failure.
+   \retval #OP_EREAD    The underlying seek operation failed.
+   \retval #OP_EINVAL   The stream was only partially open, or the target was
+                         outside the valid range for the stream.
+   \retval #OP_ENOSEEK  This stream is not seekable.
+   \retval #OP_EBADLINK Failed to initialize a decoder for a stream for an
+                         unknown reason.*/
+int op_raw_seek(OggOpusFile *_of,opus_int64 _byte_offset) OP_ARG_NONNULL(1);
+
+/**Seek to the specified PCM offset, such that decoding will begin at exactly
+    the requested position.
+   \param _of         The \c OggOpusFile in which to seek.
+   \param _pcm_offset The PCM offset to seek to.
+                      This is in samples at 48 kHz relative to the start of the
+                       stream.
+   \return 0 on success, or a negative value on error.
+   \retval #OP_EREAD    An underlying read or seek operation failed.
+   \retval #OP_EINVAL   The stream was only partially open, or the target was
+                         outside the valid range for the stream.
+   \retval #OP_ENOSEEK  This stream is not seekable.
+   \retval #OP_EBADLINK We failed to find data we had seen before, or the
+                         bitstream structure was sufficiently malformed that
+                         seeking to the target destination was impossible.*/
+int op_pcm_seek(OggOpusFile *_of,ogg_int64_t _pcm_offset) OP_ARG_NONNULL(1);
+
+/*@}*/
+/*@}*/
+
+/**\defgroup stream_decoding Decoding*/
+/*@{*/
+/**\name Functions for decoding audio data
+
+   These functions retrieve actual decoded audio data from the stream.
+   The general functions, op_read() and op_read_float() return 16-bit or
+    floating-point output, both using native endian ordering.
+   The number of channels returned can change from link to link in a chained
+    stream.
+   There are special functions, op_read_stereo() and op_read_float_stereo(),
+    which always output two channels, to simplify applications which do not
+    wish to handle multichannel audio.
+   These downmix multichannel files to two channels, so they can always return
+    samples in the same format for every link in a chained file.
+
+   If the rest of your audio processing chain can handle floating point, the
+    floating-point routines should be preferred, as they prevent clipping and
+    other issues which might be avoided entirely if, e.g., you scale down the
+    volume at some other stage.
+   However, if you intend to consume 16-bit samples directly, the conversion in
+    <tt>libopusfile</tt> provides noise-shaping dithering and, if compiled
+    against <tt>libopus</tt>&nbsp;1.1 or later, soft-clipping prevention.
+
+   <tt>libopusfile</tt> can also be configured at compile time to use the
+    fixed-point <tt>libopus</tt> API.
+   If so, <tt>libopusfile</tt>'s floating-point API may also be disabled.
+   In that configuration, nothing in <tt>libopusfile</tt> will use any
+    floating-point operations, to simplify support on devices without an
+    adequate FPU.
+
+   \warning HTTPS streams may be be vulnerable to truncation attacks if you do
+    not check the error return code from op_read_float() or its associated
+    functions.
+   If the remote peer does not close the connection gracefully (with a TLS
+    "close notify" message), these functions will return #OP_EREAD instead of 0
+    when they reach the end of the file.
+   If you are reading from an <https:> URL (particularly if seeking is not
+    supported), you should make sure to check for this error and warn the user
+    appropriately.*/
+/*@{*/
+
+/**Indicates that the decoding callback should produce signed 16-bit
+    native-endian output samples.*/
+#define OP_DEC_FORMAT_SHORT (7008)
+/**Indicates that the decoding callback should produce 32-bit native-endian
+    float samples.*/
+#define OP_DEC_FORMAT_FLOAT (7040)
+
+/**Indicates that the decoding callback did not decode anything, and that
+    <tt>libopusfile</tt> should decode normally instead.*/
+#define OP_DEC_USE_DEFAULT  (6720)
+
+/**Called to decode an Opus packet.
+   This should invoke the functional equivalent of opus_multistream_decode() or
+    opus_multistream_decode_float(), except that it returns 0 on success
+    instead of the number of decoded samples (which is known a priori).
+   \param _ctx       The application-provided callback context.
+   \param _decoder   The decoder to use to decode the packet.
+   \param[out] _pcm  The buffer to decode into.
+                     This will always have enough room for \a _nchannels of
+                      \a _nsamples samples, which should be placed into this
+                      buffer interleaved.
+   \param _op        The packet to decode.
+                     This will always have its granule position set to a valid
+                      value.
+   \param _nsamples  The number of samples expected from the packet.
+   \param _nchannels The number of channels expected from the packet.
+   \param _format    The desired sample output format.
+                     This is either #OP_DEC_FORMAT_SHORT or
+                      #OP_DEC_FORMAT_FLOAT.
+   \param _li        The index of the link from which this packet was decoded.
+   \return A non-negative value on success, or a negative value on error.
+           Any error codes should be the same as those returned by
+            opus_multistream_decode() or opus_multistream_decode_float().
+           Success codes are as follows:
+   \retval 0                   Decoding was successful.
+                               The application has filled the buffer with
+                                exactly <code>\a _nsamples*\a
+                                _nchannels</code> samples in the requested
+                                format.
+   \retval #OP_DEC_USE_DEFAULT No decoding was done.
+                               <tt>libopusfile</tt> should do the decoding
+                                by itself instead.*/
+typedef int (*op_decode_cb_func)(void *_ctx,OpusMSDecoder *_decoder,void *_pcm,
+ const ogg_packet *_op,int _nsamples,int _nchannels,int _format,int _li);
+
+/**Sets the packet decode callback function.
+   If set, this is called once for each packet that needs to be decoded.
+   This can be used by advanced applications to do additional processing on the
+    compressed or uncompressed data.
+   For example, an application might save the final entropy coder state for
+    debugging and testing purposes, or it might apply additional filters
+    before the downmixing, dithering, or soft-clipping performed by
+    <tt>libopusfile</tt>, so long as these filters do not introduce any
+    latency.
+
+   A call to this function is no guarantee that the audio will eventually be
+    delivered to the application.
+   <tt>libopusfile</tt> may discard some or all of the decoded audio data
+    (i.e., at the beginning or end of a link, or after a seek), however the
+    callback is still required to provide all of it.
+   \param _of        The \c OggOpusFile on which to set the decode callback.
+   \param _decode_cb The callback function to call.
+                     This may be <code>NULL</code> to disable calling the
+                      callback.
+   \param _ctx       The application-provided context pointer to pass to the
+                      callback on each call.*/
+void op_set_decode_callback(OggOpusFile *_of,
+ op_decode_cb_func _decode_cb,void *_ctx) OP_ARG_NONNULL(1);
+
+/**Gain offset type that indicates that the provided offset is relative to the
+    header gain.
+   This is the default.*/
+#define OP_HEADER_GAIN   (0)
+
+/**Gain offset type that indicates that the provided offset is relative to the
+    R128_ALBUM_GAIN value (if any), in addition to the header gain.*/
+#define OP_ALBUM_GAIN    (3007)
+
+/**Gain offset type that indicates that the provided offset is relative to the
+    R128_TRACK_GAIN value (if any), in addition to the header gain.*/
+#define OP_TRACK_GAIN    (3008)
+
+/**Gain offset type that indicates that the provided offset should be used as
+    the gain directly, without applying any the header or track gains.*/
+#define OP_ABSOLUTE_GAIN (3009)
+
+/**Sets the gain to be used for decoded output.
+   By default, the gain in the header is applied with no additional offset.
+   The total gain (including header gain and/or track gain, if applicable, and
+    this offset), will be clamped to [-32768,32767]/256 dB.
+   This is more than enough to saturate or underflow 16-bit PCM.
+   \note The new gain will not be applied to any already buffered, decoded
+    output.
+   This means you cannot change it sample-by-sample, as at best it will be
+    updated packet-by-packet.
+   It is meant for setting a target volume level, rather than applying smooth
+    fades, etc.
+   \param _of             The \c OggOpusFile on which to set the gain offset.
+   \param _gain_type      One of #OP_HEADER_GAIN, #OP_ALBUM_GAIN,
+                           #OP_TRACK_GAIN, or #OP_ABSOLUTE_GAIN.
+   \param _gain_offset_q8 The gain offset to apply, in 1/256ths of a dB.
+   \return 0 on success or a negative value on error.
+   \retval #OP_EINVAL The \a _gain_type was unrecognized.*/
+int op_set_gain_offset(OggOpusFile *_of,
+ int _gain_type,opus_int32 _gain_offset_q8) OP_ARG_NONNULL(1);
+
+/**Sets whether or not dithering is enabled for 16-bit decoding.
+   By default, when <tt>libopusfile</tt> is compiled to use floating-point
+    internally, calling op_read() or op_read_stereo() will first decode to
+    float, and then convert to fixed-point using noise-shaping dithering.
+   This flag can be used to disable that dithering.
+   When the application uses op_read_float() or op_read_float_stereo(), or when
+    the library has been compiled to decode directly to fixed point, this flag
+    has no effect.
+   \param _of      The \c OggOpusFile on which to enable or disable dithering.
+   \param _enabled A non-zero value to enable dithering, or 0 to disable it.*/
+void op_set_dither_enabled(OggOpusFile *_of,int _enabled) OP_ARG_NONNULL(1);
+
+/**Reads more samples from the stream.
+   \note Although \a _buf_size must indicate the total number of values that
+    can be stored in \a _pcm, the return value is the number of samples
+    <em>per channel</em>.
+   This is done because
+   <ol>
+   <li>The channel count cannot be known a priori (reading more samples might
+        advance us into the next link, with a different channel count), so
+        \a _buf_size cannot also be in units of samples per channel,</li>
+   <li>Returning the samples per channel matches the <code>libopus</code> API
+        as closely as we're able,</li>
+   <li>Returning the total number of values instead of samples per channel
+        would mean the caller would need a division to compute the samples per
+        channel, and might worry about the possibility of getting back samples
+        for some channels and not others, and</li>
+   <li>This approach is relatively fool-proof: if an application passes too
+        small a value to \a _buf_size, they will simply get fewer samples back,
+        and if they assume the return value is the total number of values, then
+        they will simply read too few (rather than reading too many and going
+        off the end of the buffer).</li>
+   </ol>
+   \param      _of       The \c OggOpusFile from which to read.
+   \param[out] _pcm      A buffer in which to store the output PCM samples, as
+                          signed native-endian 16-bit values at 48&nbsp;kHz
+                          with a nominal range of <code>[-32768,32767)</code>.
+                         Multiple channels are interleaved using the
+                          <a href="http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-800004.3.9">Vorbis
+                          channel ordering</a>.
+                         This must have room for at least \a _buf_size values.
+   \param      _buf_size The number of values that can be stored in \a _pcm.
+                         It is recommended that this be large enough for at
+                          least 120 ms of data at 48 kHz per channel (5760
+                          values per channel).
+                         Smaller buffers will simply return less data, possibly
+                          consuming more memory to buffer the data internally.
+                         <tt>libopusfile</tt> may return less data than
+                          requested.
+                         If so, there is no guarantee that the remaining data
+                          in \a _pcm will be unmodified.
+   \param[out] _li       The index of the link this data was decoded from.
+                         You may pass <code>NULL</code> if you do not need this
+                          information.
+                         If this function fails (returning a negative value),
+                          this parameter is left unset.
+   \return The number of samples read per channel on success, or a negative
+            value on failure.
+           The channel count can be retrieved on success by calling
+            <code>op_head(_of,*_li)</code>.
+           The number of samples returned may be 0 if the buffer was too small
+            to store even a single sample for all channels, or if end-of-file
+            was reached.
+           The list of possible failure codes follows.
+           Most of them can only be returned by unseekable, chained streams
+            that encounter a new link.
+   \retval #OP_HOLE          There was a hole in the data, and some samples
+                              may have been skipped.
+                             Call this function again to continue decoding
+                              past the hole.
+   \retval #OP_EREAD         An underlying read operation failed.
+                             This may signal a truncation attack from an
+                              <https:> source.
+   \retval #OP_EFAULT        An internal memory allocation failed.
+   \retval #OP_EIMPL         An unseekable stream encountered a new link that
+                              used a feature that is not implemented, such as
+                              an unsupported channel family.
+   \retval #OP_EINVAL        The stream was only partially open.
+   \retval #OP_ENOTFORMAT    An unseekable stream encountered a new link that
+                              did not have any logical Opus streams in it.
+   \retval #OP_EBADHEADER    An unseekable stream encountered a new link with a
+                              required header packet that was not properly
+                              formatted, contained illegal values, or was
+                              missing altogether.
+   \retval #OP_EVERSION      An unseekable stream encountered a new link with
+                              an ID header that contained an unrecognized
+                              version number.
+   \retval #OP_EBADPACKET    Failed to properly decode the next packet.
+   \retval #OP_EBADLINK      We failed to find data we had seen before.
+   \retval #OP_EBADTIMESTAMP An unseekable stream encountered a new link with
+                              a starting timestamp that failed basic validity
+                              checks.*/
+OP_WARN_UNUSED_RESULT int op_read(OggOpusFile *_of,
+ opus_int16 *_pcm,int _buf_size,int *_li) OP_ARG_NONNULL(1);
+
+/**Reads more samples from the stream.
+   \note Although \a _buf_size must indicate the total number of values that
+    can be stored in \a _pcm, the return value is the number of samples
+    <em>per channel</em>.
+   <ol>
+   <li>The channel count cannot be known a priori (reading more samples might
+        advance us into the next link, with a different channel count), so
+        \a _buf_size cannot also be in units of samples per channel,</li>
+   <li>Returning the samples per channel matches the <code>libopus</code> API
+        as closely as we're able,</li>
+   <li>Returning the total number of values instead of samples per channel
+        would mean the caller would need a division to compute the samples per
+        channel, and might worry about the possibility of getting back samples
+        for some channels and not others, and</li>
+   <li>This approach is relatively fool-proof: if an application passes too
+        small a value to \a _buf_size, they will simply get fewer samples back,
+        and if they assume the return value is the total number of values, then
+        they will simply read too few (rather than reading too many and going
+        off the end of the buffer).</li>
+   </ol>
+   \param      _of       The \c OggOpusFile from which to read.
+   \param[out] _pcm      A buffer in which to store the output PCM samples as
+                          signed floats at 48&nbsp;kHz with a nominal range of
+                          <code>[-1.0,1.0]</code>.
+                         Multiple channels are interleaved using the
+                          <a href="http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-800004.3.9">Vorbis
+                          channel ordering</a>.
+                         This must have room for at least \a _buf_size floats.
+   \param      _buf_size The number of floats that can be stored in \a _pcm.
+                         It is recommended that this be large enough for at
+                          least 120 ms of data at 48 kHz per channel (5760
+                          samples per channel).
+                         Smaller buffers will simply return less data, possibly
+                          consuming more memory to buffer the data internally.
+                         If less than \a _buf_size values are returned,
+                          <tt>libopusfile</tt> makes no guarantee that the
+                          remaining data in \a _pcm will be unmodified.
+   \param[out] _li       The index of the link this data was decoded from.
+                         You may pass <code>NULL</code> if you do not need this
+                          information.
+                         If this function fails (returning a negative value),
+                          this parameter is left unset.
+   \return The number of samples read per channel on success, or a negative
+            value on failure.
+           The channel count can be retrieved on success by calling
+            <code>op_head(_of,*_li)</code>.
+           The number of samples returned may be 0 if the buffer was too small
+            to store even a single sample for all channels, or if end-of-file
+            was reached.
+           The list of possible failure codes follows.
+           Most of them can only be returned by unseekable, chained streams
+            that encounter a new link.
+   \retval #OP_HOLE          There was a hole in the data, and some samples
+                              may have been skipped.
+                             Call this function again to continue decoding
+                              past the hole.
+   \retval #OP_EREAD         An underlying read operation failed.
+                             This may signal a truncation attack from an
+                              <https:> source.
+   \retval #OP_EFAULT        An internal memory allocation failed.
+   \retval #OP_EIMPL         An unseekable stream encountered a new link that
+                              used a feature that is not implemented, such as
+                              an unsupported channel family.
+   \retval #OP_EINVAL        The stream was only partially open.
+   \retval #OP_ENOTFORMAT    An unseekable stream encountered a new link that
+                              did not have any logical Opus streams in it.
+   \retval #OP_EBADHEADER    An unseekable stream encountered a new link with a
+                              required header packet that was not properly
+                              formatted, contained illegal values, or was
+                              missing altogether.
+   \retval #OP_EVERSION      An unseekable stream encountered a new link with
+                              an ID header that contained an unrecognized
+                              version number.
+   \retval #OP_EBADPACKET    Failed to properly decode the next packet.
+   \retval #OP_EBADLINK      We failed to find data we had seen before.
+   \retval #OP_EBADTIMESTAMP An unseekable stream encountered a new link with
+                              a starting timestamp that failed basic validity
+                              checks.*/
+OP_WARN_UNUSED_RESULT int op_read_float(OggOpusFile *_of,
+ float *_pcm,int _buf_size,int *_li) OP_ARG_NONNULL(1);
+
+/**Reads more samples from the stream and downmixes to stereo, if necessary.
+   This function is intended for simple players that want a uniform output
+    format, even if the channel count changes between links in a chained
+    stream.
+   \note \a _buf_size indicates the total number of values that can be stored
+    in \a _pcm, while the return value is the number of samples <em>per
+    channel</em>, even though the channel count is known, for consistency with
+    op_read().
+   \param      _of       The \c OggOpusFile from which to read.
+   \param[out] _pcm      A buffer in which to store the output PCM samples, as
+                          signed native-endian 16-bit values at 48&nbsp;kHz
+                          with a nominal range of <code>[-32768,32767)</code>.
+                         The left and right channels are interleaved in the
+                          buffer.
+                         This must have room for at least \a _buf_size values.
+   \param      _buf_size The number of values that can be stored in \a _pcm.
+                         It is recommended that this be large enough for at
+                          least 120 ms of data at 48 kHz per channel (11520
+                          values total).
+                         Smaller buffers will simply return less data, possibly
+                          consuming more memory to buffer the data internally.
+                         If less than \a _buf_size values are returned,
+                          <tt>libopusfile</tt> makes no guarantee that the
+                          remaining data in \a _pcm will be unmodified.
+   \return The number of samples read per channel on success, or a negative
+            value on failure.
+           The number of samples returned may be 0 if the buffer was too small
+            to store even a single sample for both channels, or if end-of-file
+            was reached.
+           The list of possible failure codes follows.
+           Most of them can only be returned by unseekable, chained streams
+            that encounter a new link.
+   \retval #OP_HOLE          There was a hole in the data, and some samples
+                              may have been skipped.
+                             Call this function again to continue decoding
+                              past the hole.
+   \retval #OP_EREAD         An underlying read operation failed.
+                             This may signal a truncation attack from an
+                              <https:> source.
+   \retval #OP_EFAULT        An internal memory allocation failed.
+   \retval #OP_EIMPL         An unseekable stream encountered a new link that
+                              used a feature that is not implemented, such as
+                              an unsupported channel family.
+   \retval #OP_EINVAL        The stream was only partially open.
+   \retval #OP_ENOTFORMAT    An unseekable stream encountered a new link that
+                              did not have any logical Opus streams in it.
+   \retval #OP_EBADHEADER    An unseekable stream encountered a new link with a
+                              required header packet that was not properly
+                              formatted, contained illegal values, or was
+                              missing altogether.
+   \retval #OP_EVERSION      An unseekable stream encountered a new link with
+                              an ID header that contained an unrecognized
+                              version number.
+   \retval #OP_EBADPACKET    Failed to properly decode the next packet.
+   \retval #OP_EBADLINK      We failed to find data we had seen before.
+   \retval #OP_EBADTIMESTAMP An unseekable stream encountered a new link with
+                              a starting timestamp that failed basic validity
+                              checks.*/
+OP_WARN_UNUSED_RESULT int op_read_stereo(OggOpusFile *_of,
+ opus_int16 *_pcm,int _buf_size) OP_ARG_NONNULL(1);
+
+/**Reads more samples from the stream and downmixes to stereo, if necessary.
+   This function is intended for simple players that want a uniform output
+    format, even if the channel count changes between links in a chained
+    stream.
+   \note \a _buf_size indicates the total number of values that can be stored
+    in \a _pcm, while the return value is the number of samples <em>per
+    channel</em>, even though the channel count is known, for consistency with
+    op_read_float().
+   \param      _of       The \c OggOpusFile from which to read.
+   \param[out] _pcm      A buffer in which to store the output PCM samples, as
+                          signed floats at 48&nbsp;kHz with a nominal range of
+                          <code>[-1.0,1.0]</code>.
+                         The left and right channels are interleaved in the
+                          buffer.
+                         This must have room for at least \a _buf_size values.
+   \param      _buf_size The number of values that can be stored in \a _pcm.
+                         It is recommended that this be large enough for at
+                          least 120 ms of data at 48 kHz per channel (11520
+                          values total).
+                         Smaller buffers will simply return less data, possibly
+                          consuming more memory to buffer the data internally.
+                         If less than \a _buf_size values are returned,
+                          <tt>libopusfile</tt> makes no guarantee that the
+                          remaining data in \a _pcm will be unmodified.
+   \return The number of samples read per channel on success, or a negative
+            value on failure.
+           The number of samples returned may be 0 if the buffer was too small
+            to store even a single sample for both channels, or if end-of-file
+            was reached.
+           The list of possible failure codes follows.
+           Most of them can only be returned by unseekable, chained streams
+            that encounter a new link.
+   \retval #OP_HOLE          There was a hole in the data, and some samples
+                              may have been skipped.
+                             Call this function again to continue decoding
+                              past the hole.
+   \retval #OP_EREAD         An underlying read operation failed.
+                             This may signal a truncation attack from an
+                              <https:> source.
+   \retval #OP_EFAULT        An internal memory allocation failed.
+   \retval #OP_EIMPL         An unseekable stream encountered a new link that
+                              used a feature that is not implemented, such as
+                              an unsupported channel family.
+   \retval #OP_EINVAL        The stream was only partially open.
+   \retval #OP_ENOTFORMAT    An unseekable stream encountered a new link that
+                              that did not have any logical Opus streams in it.
+   \retval #OP_EBADHEADER    An unseekable stream encountered a new link with a
+                              required header packet that was not properly
+                              formatted, contained illegal values, or was
+                              missing altogether.
+   \retval #OP_EVERSION      An unseekable stream encountered a new link with
+                              an ID header that contained an unrecognized
+                              version number.
+   \retval #OP_EBADPACKET    Failed to properly decode the next packet.
+   \retval #OP_EBADLINK      We failed to find data we had seen before.
+   \retval #OP_EBADTIMESTAMP An unseekable stream encountered a new link with
+                              a starting timestamp that failed basic validity
+                              checks.*/
+OP_WARN_UNUSED_RESULT int op_read_float_stereo(OggOpusFile *_of,
+ float *_pcm,int _buf_size) OP_ARG_NONNULL(1);
+
+/*@}*/
+/*@}*/
+
+# if OP_GNUC_PREREQ(4,0)
+#  pragma GCC visibility pop
+# endif
+
+# if defined(__cplusplus)
+}
+# endif
+
+#endif