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Diffstat (limited to 'modules/mpa/mpa.c')
| -rw-r--r-- | modules/mpa/mpa.c | 201 |
1 files changed, 201 insertions, 0 deletions
diff --git a/modules/mpa/mpa.c b/modules/mpa/mpa.c new file mode 100644 index 0000000..88ebfbe --- /dev/null +++ b/modules/mpa/mpa.c @@ -0,0 +1,201 @@ +/** + * @file mpa.c mpa Audio Codec + * + * Copyright (C) 2016 Symonics GmbH + */ + +#include <re.h> +#include <baresip.h> +#include <ctype.h> +#include <string.h> +#include "mpa.h" +#include <mpg123.h> + +/** + * @defgroup mpa mpa + * + * The mpa audio codec + * + * Supported version: + * libmpg123 1.16.0 or later + * libtwolame 0.3.13 or later + * + * References: + * + * RFC 2250 RTP Payload Format for the mpa Speech and Audio Codec + * + */ + +/* +4.1.17. Registration of MIME media type audio/MPA + + MIME media type name: audio + + MIME subtype name: MPA (MPEG audio) + + Required parameters: None + + Optional parameters: + layer: which layer of MPEG audio encoding; permissible values + are 1, 2, 3. + + samplerate: the rate at which audio is sampled. MPEG-1 audio + supports sampling rates of 32, 44.1, and 48 kHz; MPEG-2 + supports sampling rates of 16, 22.05 and 24 kHz. This parameter + is separate from the RTP timestamp clock rate which is always + 90000 Hz for MPA. + + mode: permissible values are "stereo", "joint_stereo", + "single_channel", "dual_channel". The "channels" parameter + does not apply to MPA. It is undefined to put a number of + channels in the SDP rtpmap attribute for MPA. + + bitrate: the data rate for the audio bit stream. + + ptime: RECOMMENDED duration of each packet in milliseconds. + + maxptime: maximum duration of each packet in milliseconds. + + Parameters which are omitted are left to the encoder to choose + based on the session bandwidth, configuration information, or + other constraints. The selected layer as well as the sampling + rate and mode are indicated in the payload so receivers can + process the data without these parameters being specified + externally. + + Encoding considerations: + This type is only defined for transfer via RTP [RFC 3550]. + + Security considerations: See Section 5 of RFC 3555 + + Interoperability considerations: none + + Published specification: RFC 3551 + + Applications which use this media type: + Audio and video streaming and conferencing tools. + +*/ + + +static struct aucodec mpa = { + .pt = NULL, /* for the time being, to cope +with AVT AC1 interop problems, we do not use "14" here */ + .name = "MPA", + .srate = 90000, + .ch = 1, + .fmtp = "", + .encupdh = mpa_encode_update, + .ench = mpa_encode_frm, + .decupdh = mpa_decode_update, + .dech = mpa_decode_frm, +}; + + +static int module_init(void) +{ + struct conf *conf = conf_cur(); + uint32_t value; + static char fmtp[256]; + static char mode[30]; + int res; + + /** generate fmtp string based on config file */ + + strcpy(mode,mpa.fmtp); + + if (0 == conf_get_u32(conf, "mpa_bitrate", &value)) { + if (value<8000 || value>384000) { + error("MPA bitrate between 8000 and " + "384000 are allowed."); + return -1; + } + + (void)re_snprintf(fmtp+strlen(fmtp), + sizeof(fmtp)-strlen(fmtp), + "; bitrate=%d", value); + } + if (0 == conf_get_u32(conf, "mpa_layer", &value)) { + if (value<1 || value>4) { + error("MPA layer 1, 2 or 3 are allowed."); + return -1; + } + (void)re_snprintf(fmtp+strlen(fmtp), + sizeof(fmtp)-strlen(fmtp), + "; layer=%d", value); + } + if (0 == conf_get_u32(conf, "mpa_samplerate", &value)) { + switch (value) { + case 32000: + case 44100: + case 48000: + case 16000: + case 22050: + case 24000: + break; + default: + error("MPA samplerates of 16, 22.05, 24, 32, " + "44.1, and 48 kHz are allowed."); + return -1; + } + (void)re_snprintf(fmtp+strlen(fmtp), + sizeof(fmtp)-strlen(fmtp), + "; samplerate=%d", value); + } + if (0 == conf_get_str(conf, "mpa_mode", mode, sizeof(mode))) { + char *p = mode; + while (*p) { + *p = tolower(*p); + ++p; + } + + if (strcmp(mode,"stereo") + && strcmp(mode,"joint_stereo") + && strcmp(mode,"single_channel") + && strcmp(mode,"dual_channel")) { + error("MPA mode: Permissible values are stereo, " + "joint_stereo, single_channel, dual_channel"); + return -1; + } + + (void)re_snprintf(fmtp+strlen(fmtp), + sizeof(fmtp)-strlen(fmtp), + "; mode=%s", mode); + } + + if (fmtp[0]==';' && fmtp[1]==' ') + mpa.fmtp = fmtp+2; + else + mpa.fmtp = fmtp; + + /* init decoder library */ + res = mpg123_init(); + if (res != MPG123_OK) { + error("MPA libmpg123 init error %s", + mpg123_plain_strerror(res)); + return -1; + } + + aucodec_register(&mpa); + + return 0; +} + + +static int module_close(void) +{ + aucodec_unregister(&mpa); + + mpg123_exit(); + + return 0; +} + + +EXPORT_SYM const struct mod_export DECL_EXPORTS(mpa) = { + "MPA", + "audio codec", + module_init, + module_close, +}; + |