MT#61404 clone previous sequence number for T.38

If the receiver of a previously passthrough T.30 stream gets switched to
a generated PCM stream from a T.38 gateway, continue the sequencing of
the previous SSRC. Technically this is not necessary as the generated
PCM stream gets a new SSRC, but at least Asterisk seems to ignore this
and expect sequencing to continue, and will ignore PCM if the sequence
jump is too large.

Change-Id: Ia4656770db11f5fa1a1e9bf5bd71a0398deb1e00
(cherry picked from commit 18579227a9)

daemon/audio_player.c

@@ -108,7 +108,7 @@ bool audio_player_setup(struct call_media *m, const rtp_payload_type *dst_pt,
 	if (mp)
 		media_player_stop(mp);
 	else {
-		media_player_new(&mp, m->monologue);
+		media_player_new(&mp, m->monologue, NULL);
 		ap->mp = mp;
 	}
 	if (!mp)

daemon/call.c

@@ -2761,7 +2761,7 @@ static void __call_monologue_init_from_flags(struct call_monologue *ml, struct c
 
 #ifdef WITH_TRANSCODING
 	if (flags->recording_announcement) {
-		media_player_new(&ml->rec_player, ml);
+		media_player_new(&ml->rec_player, ml, NULL);
 		media_player_opts_t opts = MPO(
 				.repeat = flags->repeat_times,
 				.duration_spent = flags->repeat_duration,

daemon/media_player.c

@@ -234,7 +234,7 @@ static void __media_player_free(struct media_player *mp) {
 
 
 // call->master_lock held in W
-void media_player_new(struct media_player **mpp, struct call_monologue *ml) {
+void media_player_new(struct media_player **mpp, struct call_monologue *ml, struct ssrc_ctx *prev_ssrc) {
 #ifdef WITH_TRANSCODING
 	struct media_player *mp;
 
@@ -256,7 +256,10 @@ void media_player_new(struct media_player **mpp, struct call_monologue *ml) {
 		mp->run_func = media_player_read_packet; // default
 		mp->call = obj_get(ml->call);
 		mp->ml = ml;
-		mp->seq = ssl_random();
+		if (prev_ssrc)
+			mp->seq = atomic_get_na(&prev_ssrc->stats->ext_seq) + 1;
+		else
+			mp->seq = ssl_random();
 		mp->buffer_ts = ssl_random();
 		mp->ssrc_out = ssrc_ctx;
 	}
@@ -1601,7 +1604,7 @@ const char * call_play_media_for_ml(struct call_monologue *ml,
 	update_init_subscribers(ml, OP_PLAY_MEDIA);
 	/* media_player_new() now knows that audio player is in use
 	 * TODO: player options can have changed if already exists */
-	media_player_new(&ml->player, ml);
+	media_player_new(&ml->player, ml, NULL);
 
 	if (opts.file.len) {
 		if (!media_player_play_file(ml->player, opts))

daemon/t38.c

@@ -406,7 +406,8 @@ int t38_gateway_pair(struct call_media *t38_media, struct call_media *pcm_media,
 	if (!(tg->gw = t38_gateway_init(NULL, t38_gateway_handler, tg)))
 		goto err;
 
-	media_player_new(&tg->pcm_player, pcm_media->monologue);
+	media_player_new(&tg->pcm_player, pcm_media->monologue,
+			pcm_media->streams.length ? pcm_media->streams.head->data->ssrc_out[0] : NULL);
 	// even though we call media_player_set_media() here, we need to call it again in
 	// t38_gateway_start because our sink might not have any streams added here yet,
 	// leaving the media_player setup incomplete

include/media_player.h

@@ -121,7 +121,7 @@ struct send_timer {
 
 #define MPO(...) (media_player_opts_t){__VA_ARGS__}
 
-void media_player_new(struct media_player **, struct call_monologue *);
+void media_player_new(struct media_player **, struct call_monologue *, struct ssrc_ctx *prev_ssrc);
 bool media_player_add(struct media_player *mp, media_player_opts_t opts);
 bool media_player_start(struct media_player *);
 long long media_player_stop(struct media_player *);