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+/**
+ * @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,
+ .name = "MPA",
+ .srate = 90000,
+ .ch = 1,
+ .fmtp = "",
+ .encupdh = mpa_encode_update,
+ .ench = mpa_encode_frm,
+ .decupdh = mpa_decode_update,
+ .dech = mpa_decode_frm,
+ .plch = mpa_decode_pkloss,
+};
+
+
+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)) {
+ (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]==';')
+ mpa.fmtp = fmtp+1;
+ 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,
+};