TT#92250 add new reorder-codecs flag

Change-Id: I93587b6675540438f81193896ae8d8966b3a12a6

README.md

@@ -778,6 +778,17 @@ Optionally included keys are:
 		PCMA. With this flag however, *rtpengine* honours the single accepted codec from the
 		answer and so is able to eliminate PCMA from its own answer as it's not needed.
 
+	- `reorder codecs`
+
+		This flag adds an additional stage in the processing of the `answer` codecs. Instead of
+		accepting codecs in the same order that they were offered, reorder the list of codecs
+		to match the codecs on the opposite (answer) side. This can avoid asymmetric codec flow
+		in certain cases, at the cost of the answer message possibly listing codecs in a different
+		order from the offer message (which then could be suppressed using `single codec`).
+
+		The config option `reorder-codecs` can be set to make this the default behaviour for
+		all answer messages.
+
 	- `single codec`
 
 		Using this flag in an `answer` message will leave only the first listed codec in place

daemon/call_interfaces.c

@@ -820,6 +820,9 @@ static void call_ng_flags_flags(struct sdp_ng_flags *out, str *s, void *dummy) {
 		case CSH_LOOKUP("symmetric-codecs"):
 			out->symmetric_codecs = 1;
 			break;
+		case CSH_LOOKUP("reorder-codecs"):
+			out->reorder_codecs = 1;
+			break;
 		case CSH_LOOKUP("single-codec"):
 			out->single_codec = 1;
 			break;

daemon/codec.c

@@ -753,6 +753,35 @@ static void __accept_pt(struct call_media *receiver, struct call_media *sink, in
 		*insert_pos = (*insert_pos)->next;
 	}
 }
+static void __reorder_transcode_codecs(struct call_media *receiver, struct call_media *sink,
+		const struct sdp_ng_flags *flags, int accept_only_tc)
+{
+	// if the other side is transcoding, we need to accept codecs that were
+	// originally offered (recv->send) if we support them, even if the
+	// response (sink->send) doesn't include them
+	GList *insert_pos = NULL;
+	for (GList *l = sink->codecs_prefs_recv.head; l; l = l->next) {
+		// take the PT that we can receive on the sink side and get the appropriate
+		// output PT on the receiver side to ensure codec symmetry.
+		struct rtp_payload_type *sink_pt = l->data;
+		// determine output PT from the codec handler
+		struct codec_handler *ch = codec_handler_get(sink, sink_pt->payload_type);
+		if (ch && ch->source_pt.payload_type != -1 && ch->dest_pt.payload_type != -1) {
+			__accept_pt(receiver, sink, ch->dest_pt.payload_type, sink_pt->payload_type,
+					accept_only_tc, &insert_pos);
+			if (ch->dtmf_payload_type != -1)
+				__accept_pt(receiver, sink, ch->dtmf_payload_type, -1,
+						accept_only_tc, &insert_pos);
+			if (ch->cn_payload_type != -1)
+				__accept_pt(receiver, sink, ch->cn_payload_type, -1,
+						accept_only_tc, &insert_pos);
+		}
+		else
+			__accept_pt(receiver, sink, sink_pt->payload_type, -1, accept_only_tc, &insert_pos);
+	}
+
+	__single_codec(receiver, flags);
+}
 static void __accept_transcode_codecs(struct call_media *receiver, struct call_media *sink,
 		const struct sdp_ng_flags *flags, int accept_only_tc)
 {
@@ -903,6 +932,7 @@ static void __symmetric_codecs(struct call_media *receiver, struct call_media *s
 			struct rtp_payload_type *out_pt = g_hash_table_lookup(prefs_recv, ptype);
 			if (!out_pt)
 				continue;
+			//ilog(LOG_DEBUG, "XXXXXXXXXXXXXXXX appending recv codec " STR_FORMAT, STR_FMT(&out_pt->encoding_with_params));
 			g_hash_table_steal(prefs_recv, ptype);
 			__rtp_payload_type_add_recv(receiver, out_pt, 1);
 		}
@@ -911,6 +941,7 @@ static void __symmetric_codecs(struct call_media *receiver, struct call_media *s
 			struct rtp_payload_type *out_pt = g_hash_table_lookup(prefs_send, ptype);
 			if (!out_pt)
 				continue;
+			//ilog(LOG_DEBUG, "XXXXXXXXXXXXXXXX appending send codec " STR_FORMAT, STR_FMT(&out_pt->encoding_with_params));
 			g_hash_table_steal(prefs_send, ptype);
 			__rtp_payload_type_add_send(receiver, out_pt);
 		}
@@ -1312,8 +1343,13 @@ void codec_handlers_update(struct call_media *receiver, struct call_media *sink,
 		MEDIA_CLEAR(sink, TRANSCODE);
 	}
 
-	if (MEDIA_ISSET(sink, TRANSCODE) && (sink_transcoding & 0x2))
-		__accept_transcode_codecs(receiver, sink, flags, (receiver_transcoding & 0x1));
+	if (MEDIA_ISSET(sink, TRANSCODE) && (sink_transcoding & 0x2)) {
+		if (flags && flags->opmode == OP_ANSWER &&
+				(rtpe_config.reorder_codecs || flags->reorder_codecs))
+			__reorder_transcode_codecs(receiver, sink, flags, (receiver_transcoding & 0x1));
+		else
+			__accept_transcode_codecs(receiver, sink, flags, (receiver_transcoding & 0x1));
+	}
 	else
 		__eliminate_rejected_codecs(receiver, sink, flags);
 
@@ -1489,6 +1525,9 @@ next:
 		for (GList *l = receiver->codecs_prefs_recv.head; l; ) {
 			struct rtp_payload_type *pt = l->data;
 
+			//ilog(LOG_DEBUG, "XXXX checking recv codec " STR_FORMAT,
+					//STR_FMT(&pt->encoding));
+
 			if (pt->codec_def) {
 				// supported
 				l = l->next;

daemon/main.c

@@ -477,6 +477,7 @@ static void options(int *argc, char ***argv) {
 		{ "max-dtx",	0,0,	G_OPTION_ARG_INT,	&rtpe_config.max_dtx,	"Maximum duration of DTX handling",	"INT"},
 		{ "silence-detect",0,0,	G_OPTION_ARG_DOUBLE,	&silence_detect,	"Audio level threshold in percent for silence detection","FLOAT"},
 		{ "cn-payload",0,0,	G_OPTION_ARG_STRING_ARRAY,&cn_payload,		"Comfort noise parameters to replace silence with","INT INT INT ..."},
+		{ "reorder-codecs",0,0,	G_OPTION_ARG_NONE,	&rtpe_config.reorder_codecs,"Reorder answer codecs based on sender preference",NULL},
 #endif
 
 		{ NULL, }

daemon/rtpengine.pod

@@ -810,6 +810,11 @@ of coefficients listed (model order) is variable.
 The default values are 32 (-32 dBov) for the noise level and no spectral
 information.
 
+=item B<--reorder-codecs>
+
+Always sets the option B<reorder-codecs> in answer messages as described in the
+F<README.md>.
+
 =back
 
 =head1 INTERFACES

daemon/sdp.c

@@ -2063,10 +2063,13 @@ static int process_media_attributes(struct sdp_chopper *chop, struct sdp_media *
 
 			case ATTR_RTPMAP:
 			case ATTR_FMTP:
-			case ATTR_PTIME:
 				if (media->codecs_prefs_recv.length > 0)
 					goto strip;
 				break;
+			case ATTR_PTIME:
+				if (media->ptime)
+					goto strip;
+				break;
 			case ATTR_RTCP_FB:
 				if (attr->u.rtcp_fb.payload_type == -1)
 					break; // leave this one alone

include/call_interfaces.h

@@ -93,6 +93,7 @@ struct sdp_ng_flags {
 	    original_sendrecv:1,
 	    asymmetric_codecs:1,
 	    symmetric_codecs:1,
+	    reorder_codecs:1,
 	    single_codec:1,
 	    inject_dtmf:1,
 	    t38_decode:1,

include/main.h

@@ -110,6 +110,7 @@ struct rtpengine_config {
 	double			silence_detect_double;
 	uint32_t		silence_detect_int;
 	str			cn_payload;
+	int			reorder_codecs;
 };