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SDP: Fix interpretation of number of channels within rtpmap 

The standard says (RFC 4566 / 8866):

"For audio streams, encoding-params indicates the number of audio
channels. This parameter is OPTIONAL and may be omitted if the number
of channels is one, provided that no additional parameters
are needed."

This means that the number of channels is 1, if not specified within
rtpmap. It does not state that the codec's default value shall be used,
nor static payload definition.

Addionally the encoder always defines the number of channel. As the
encoding-params MAY be omitted, they are added to the rtpmap line, even
if the number of channels is 1.
This commit is contained in:
Andreas Eversberg 2024-02-18 18:30:49 +01:00
parent 3f77726226
commit 6ab8dc1dea
1 changed files with 15 additions and 16 deletions
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31
src/sdp.c
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@ -132,10 +132,7 @@ char *osmo_cc_session_gensdp(osmo_cc_session_t *session, int accepted_only)
osmo_cc_session_for_each_codec(media->codec_list, codec) {
if (accepted_only && !codec->accepted)
continue;
strncat_printf(sdp, "a=rtpmap:%u %s/%d", codec->payload_type_local, codec->payload_name, codec->payload_rate);
if (codec->payload_channels >= 2)
strncat_printf(sdp, "/%d", codec->payload_channels);
strncat_printf(sdp, "\r\n");
strncat_printf(sdp, "a=rtpmap:%u %s/%d/%d\r\n", codec->payload_type_local, codec->payload_name, codec->payload_rate, codec->payload_channels);
}
if (individual_send_receive) {
if (media->send && !media->receive)
@ -499,32 +496,34 @@ struct osmo_cc_session *osmo_cc_session_parsesdp(osmo_cc_session_config_t *conf,
break;
}
LOGP(DLCC, LOGL_DEBUG, " -> (rtpmap) payload type = %d\n", codec->payload_type_remote);
if (!(word = wordsep(&next_word)))
goto rtpmap_done;
if (!(word = wordsep(&next_word))) {
rtpmap_broken:
LOGP(DLCC, LOGL_NOTICE, "Broken 'rtpmap' definition in SDP line %d = '%s' Skipping codec!\n", line_no, line);
osmo_cc_free_codec(codec);
break;
}
if ((p = strchr(word, '/')))
*p++ = '\0';
free((char *)codec->payload_name); // in case it is already set above
codec->payload_name = strdup(word);
LOGP(DLCC, LOGL_DEBUG, " -> (rtpmap) payload name = %s\n", codec->payload_name);
if (!(word = p))
goto rtpmap_done;
goto rtpmap_broken;
if ((p = strchr(word, '/')))
*p++ = '\0';
codec->payload_rate = atoi(word);
LOGP(DLCC, LOGL_DEBUG, " -> (rtpmap) payload rate = %d\n", codec->payload_rate);
if (!(word = p)) {
/* if no channel is given and no default was specified, we must set 1 channel */
if (!codec->payload_channels)
codec->payload_channels = 1;
goto rtpmap_done;
/* For audio streams, encoding-params indicates the number of audio channels.
* This parameter is OPTIONAL and may be omitted if the number of channels is
* one, provided that no additional parameters are needed. */
codec->payload_channels = 1;
LOGP(DLCC, LOGL_DEBUG, " -> (rtpmap) payload channels = %d (default)\n", codec->payload_channels);
break;
}
codec->payload_channels = atoi(word);
LOGP(DLCC, LOGL_DEBUG, " -> (rtpmap) payload channels = %d\n", codec->payload_channels);
rtpmap_done:
if (!codec->payload_name || !codec->payload_rate || !codec->payload_channels) {
LOGP(DLCC, LOGL_NOTICE, "Broken 'rtpmap' definition in SDP line %d = '%s' Skipping codec!\n", line_no, line);
osmo_cc_free_codec(codec);
}
break;
}
break;
}