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mgcp: Turn SDP file parsing in a two stage process 

First collect everything we know and the mapping. E.g. a genuis
could remap "3" to "AMR" so we only know the codecs once we are
at the end of the SDP file. Once we have collected everything we
can select the audio codecs. The current code is compatible in
that two codecs will be selected regardless of if they make any
sense or not.

mgcp_set_audio_info could re-use some of our codec information
but then the caller in the MGCP protocol needs to be updated as
well as we use the "I: GSM" information to derive the codec from
there.
This commit is contained in:
Holger Hans Peter Freyther 2015-08-14 11:11:51 +02:00
parent a611da8407
commit ca7d05bdb9
1 changed files with 108 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

136
openbsc/src/libmgcp/mgcp_sdp.c
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@ -25,6 +25,18 @@
#include <errno.h>
struct sdp_rtp_map {
/* the type */
int payload_type;
/* null, static or later dynamic codec name */
char *codec_name;
/* A pointer to the original line for later parsing */
char *map_line;
int rate;
int channels;
};
int mgcp_set_audio_info(void *ctx, struct mgcp_rtp_codec *codec,
int payload_type, const char *audio_name)
{
@ -91,14 +103,69 @@ int mgcp_set_audio_info(void *ctx, struct mgcp_rtp_codec *codec,
return 0;
}
void codecs_initialize(void *ctx, struct sdp_rtp_map *codecs, int used)
{
int i;
for (i = 0; i < used; ++i) {
switch (codecs[i].payload_type) {
case 3:
codecs[i].codec_name = "GSM";
codecs[i].rate = 8000;
codecs[i].channels = 1;
break;
case 8:
codecs[i].codec_name = "PCMA";
codecs[i].rate = 8000;
codecs[i].channels = 1;
break;
case 18:
codecs[i].codec_name = "G729";
codecs[i].rate = 8000;
codecs[i].channels = 1;
break;
}
}
}
void codecs_update(void *ctx, struct sdp_rtp_map *codecs, int used, int payload, char *audio_name)
{
int i;
for (i = 0; i < used; ++i) {
char audio_codec[64];
int rate = -1;
int channels = -1;
if (codecs[i].payload_type != payload)
continue;
if (sscanf(audio_name, "%63[^/]/%d/%d",
audio_codec, &rate, &channels) < 1) {
LOGP(DMGCP, LOGL_ERROR, "Failed to parse '%s'\n", audio_name);
continue;
}
codecs[i].map_line = talloc_strdup(ctx, audio_name);
codecs[i].codec_name = talloc_strdup(ctx, audio_codec);
codecs[i].rate = rate;
codecs[i].channels = channels;
return;
}
LOGP(DMGCP, LOGL_ERROR, "Unconfigured PT(%d) with %s\n", payload, audio_name);
}
int mgcp_parse_sdp_data(struct mgcp_rtp_end *rtp, struct mgcp_parse_data *p)
{
struct sdp_rtp_map codecs[10];
int codecs_used = 0;
char *line;
int found_media = 0;
/* TODO/XXX make it more generic */
int audio_payload = -1;
int audio_payload_alt = -1;
int maxptime = -1;
int i;
int codecs_assigned = 0;
void *tmp_ctx = talloc_new(NULL);
memset(&codecs, 0, sizeof(codecs));
for_each_line(line, p->save) {
switch (line[0]) {
@ -113,17 +180,10 @@ int mgcp_parse_sdp_data(struct mgcp_rtp_end *rtp, struct mgcp_parse_data *p)
int ptime, ptime2 = 0;
char audio_name[64];
if (audio_payload == -1)
break;
if (sscanf(line, "a=rtpmap:%d %63s",
&payload, audio_name) == 2) {
if (payload == audio_payload)
mgcp_set_audio_info(p->cfg, &rtp->codec,
payload, audio_name);
else if (payload == audio_payload_alt)
mgcp_set_audio_info(p->cfg, &rtp->alt_codec,
payload, audio_name);
codecs_update(tmp_ctx, codecs, codecs_used, payload, audio_name);
} else if (sscanf(line, "a=ptime:%d-%d",
&ptime, &ptime2) >= 1) {
if (ptime2 > 0 && ptime2 != ptime)
@ -131,29 +191,30 @@ int mgcp_parse_sdp_data(struct mgcp_rtp_end *rtp, struct mgcp_parse_data *p)
else
rtp->packet_duration_ms = ptime;
} else if (sscanf(line, "a=maxptime:%d", &ptime2) == 1) {
/* TODO/XXX: Store this per codec and derive it on use */
if (ptime2 * rtp->codec.frame_duration_den >
rtp->codec.frame_duration_num * 1500)
/* more than 1 frame */
rtp->packet_duration_ms = 0;
maxptime = ptime2;
}
break;
}
case 'm': {
int port, rc;
audio_payload = -1;
audio_payload_alt = -1;
rc = sscanf(line, "m=audio %d RTP/AVP %d %d",
&port, &audio_payload, &audio_payload_alt);
rc = sscanf(line, "m=audio %d RTP/AVP %d %d %d %d %d %d %d %d %d %d",
&port,
&codecs[0].payload_type,
&codecs[1].payload_type,
&codecs[2].payload_type,
&codecs[3].payload_type,
&codecs[4].payload_type,
&codecs[5].payload_type,
&codecs[6].payload_type,
&codecs[7].payload_type,
&codecs[8].payload_type,
&codecs[9].payload_type);
if (rc >= 2) {
rtp->rtp_port = htons(port);
rtp->rtcp_port = htons(port + 1);
found_media = 1;
mgcp_set_audio_info(p->cfg, &rtp->codec, audio_payload, NULL);
if (rc == 3)
mgcp_set_audio_info(p->cfg, &rtp->alt_codec,
audio_payload_alt, NULL);
codecs_used = rc - 1;
codecs_initialize(tmp_ctx, codecs, codecs_used);
}
break;
}
@ -178,14 +239,33 @@ int mgcp_parse_sdp_data(struct mgcp_rtp_end *rtp, struct mgcp_parse_data *p)
}
}
if (found_media)
/* Now select the primary and alt_codec */
for (i = 0; i < codecs_used && codecs_assigned < 2; ++i) {
struct mgcp_rtp_codec *codec = codecs_assigned == 0 ?
&rtp->codec : &rtp->alt_codec;
mgcp_set_audio_info(p->cfg, codec,
codecs[i].payload_type,
codecs[i].map_line);
codecs_assigned += 1;
}
if (codecs_assigned > 0) {
/* TODO/XXX: Store this per codec and derive it on use */
if (maxptime >= 0 && maxptime * rtp->codec.frame_duration_den >
rtp->codec.frame_duration_num * 1500) {
/* more than 1 frame */
rtp->packet_duration_ms = 0;
}
LOGP(DMGCP, LOGL_NOTICE,
"Got media info via SDP: port %d, payload %d (%s), "
"duration %d, addr %s\n",
ntohs(rtp->rtp_port), rtp->codec.payload_type,
rtp->codec.subtype_name ? rtp->codec.subtype_name : "unknown",
rtp->packet_duration_ms, inet_ntoa(rtp->addr));
}
return found_media;
talloc_free(tmp_ctx);
return codecs_assigned > 0;
}