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

@@ -2690,7 +2690,7 @@ 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);
 		bool ret = true;
 		media_player_opts_t opts = MPO(
 				.repeat = flags->repeat_times,

daemon/call_interfaces.c

@@ -3494,7 +3494,7 @@ const char *call_play_media_ng(bencode_item_t *input, bencode_item_t *output) {
 		// media_player_new() now knows that audio player is in use
 
 		// TODO: player options can have changed if already exists
-		media_player_new(&monologue->player, monologue);
+		media_player_new(&monologue->player, monologue, NULL);
 
 		media_player_opts_t opts = MPO(
 				.repeat = flags.repeat_times,

daemon/media_player.c

@@ -184,7 +184,7 @@ static void __media_player_free(void *p) {
 
 
 // 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
 	if (*mpp)
 		return;
@@ -206,7 +206,10 @@ 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;
 

daemon/t38.c

@@ -407,7 +407,8 @@ 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

@@ -114,7 +114,7 @@ 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_play_file(struct media_player *, const str *, media_player_opts_t);
 bool media_player_play_blob(struct media_player *, const str *, media_player_opts_t);
 bool media_player_play_db(struct media_player *, long long, media_player_opts_t);