TT#36301 add `always-transcode` flag

closes #527

Change-Id: I0d8192cf93c49823f35a6307ccd8c77842fb51dd

README.md

@@ -1176,6 +1176,18 @@ Optionally included keys are:
 		attribute already present in the SDP, it will leave the SDP untouched and not process
 		the message.
 
+	- `always transcode`
+
+		When transcoding is in use, *rtpengine* will normally match up the codecs offered with
+		one side with the codecs offered by the other side, and engage the transcoding engine
+		only for codec pairs that are not supported by both sides. With this flag present,
+		*rtpengine* will skip the codec match-up routine and always trancode any received media
+		to the first (highest priority) codec offered by the other side that is supported for
+		transcoding. Using this flag engages the transcoding engine even if no other
+		`transcoding` flags are present. Unlike other transcoding options, this one is directional,
+		which means that it's applied only to the one side doing the signalling that is being
+		handled (i.e. the side doing the `offer` or the `answer`).
+
 * `replace`
 
 	Similar to the `flags` list. Controls which parts of the SDP body should be rewritten.

daemon/call.c

@@ -1653,7 +1653,7 @@ int monologue_offer_answer(struct call_monologue *other_ml, GQueue *streams,
 		codec_rtp_payload_types(media, other_media, &sp->rtp_payload_types,
 				flags->codec_strip, &flags->codec_offer, &flags->codec_transcode,
 				flags->codec_mask);
-		codec_handlers_update(media, other_media);
+		codec_handlers_update(media, other_media, flags);
 
 		/* send and recv are from our POV */
 		bf_copy_same(&media->media_flags, &sp->sp_flags,

daemon/call_interfaces.c

@@ -616,6 +616,8 @@ static void call_ng_flags_flags(struct sdp_ng_flags *out, str *s, void *dummy) {
 		out->no_rtcp_attr = 1;
 	else if (!str_cmp(s, "loop-protect"))
 		out->loop_protect = 1;
+	else if (!str_cmp(s, "always-transcode"))
+		out->always_transcode = 1;
 	else {
 		// handle values aliases from other dictionaries
 		if (call_ng_flags_prefix(out, s, "SDES-", ng_sdes_option, NULL))

daemon/call_interfaces.h

@@ -59,6 +59,7 @@ struct sdp_ng_flags {
 	    reset:1,
 	    record_call:1,
 	    loop_protect:1,
+	    always_transcode:1,
 	    supports_load_limit:1,
 	    dtls_off:1,
 	    sdes_off:1,

daemon/codec.c

@@ -9,6 +9,7 @@
 #include "codeclib.h"
 #include "ssrc.h"
 #include "rtcp.h"
+#include "call_interfaces.h"
 
 
 
@@ -158,7 +159,9 @@ static GList *__delete_receiver_codec(struct call_media *receiver, GList *link)
 }
 
 // call must be locked in W
-void codec_handlers_update(struct call_media *receiver, struct call_media *sink) {
+void codec_handlers_update(struct call_media *receiver, struct call_media *sink,
+		const struct sdp_ng_flags *flags)
+{
 	if (!receiver->codec_handlers)
 		receiver->codec_handlers = g_hash_table_new_full(g_int_hash, g_int_equal,
 				NULL, __codec_handler_free);
@@ -302,7 +305,9 @@ void codec_handlers_update(struct call_media *receiver, struct call_media *sink)
 
 		// in case of ptime mismatch, we transcode
 		//struct rtp_payload_type *dest_pt = g_hash_table_lookup(sink->codec_names_send, &pt->encoding);
-		GQueue *dest_codecs = g_hash_table_lookup(sink->codec_names_send, &pt->encoding);
+		GQueue *dest_codecs = NULL;
+		if (!flags || !flags->always_transcode)
+			dest_codecs = g_hash_table_lookup(sink->codec_names_send, &pt->encoding);
 		if (dest_codecs) {
 			// the sink supports this codec - check offered formats
 			dest_pt = NULL;

daemon/codec.h

@@ -13,6 +13,7 @@ struct call_media;
 struct codec_handler;
 struct media_packet;
 struct ssrc_hash;
+struct sdp_ng_flags;
 
 
 typedef int codec_handler_func(struct codec_handler *, struct call_media *, struct media_packet *);
@@ -56,7 +57,7 @@ void __rtp_payload_type_add_send(struct call_media *other_media, struct rtp_payl
 
 #ifdef WITH_TRANSCODING
 
-void codec_handlers_update(struct call_media *receiver, struct call_media *sink);
+void codec_handlers_update(struct call_media *receiver, struct call_media *sink, const struct sdp_ng_flags *);
 
 #else
 

daemon/redis.c

@@ -1413,7 +1413,7 @@ static int json_link_medias(struct call *c, struct redis_list *medias,
 		for (GList *l = other_ml->medias.head; l; l = l->next) {
 			struct call_media *other_m = l->data;
 			if (other_m->index == med->index) {
-				codec_handlers_update(med, other_m);
+				codec_handlers_update(med, other_m, NULL);
 				break;
 			}
 		}

utils/rtpengine-ng-client

@@ -56,6 +56,7 @@ GetOptions(
 	'flags=s@'			=> \$options{'flags'},
 	'supports=s@'			=> \$options{'supports'},
 	'xmlrpc-callback=s'		=> \$options{'xmlrpc-callback'},
+	'always-transcode'		=> \$options{'always transcode'},
 ) or die;
 
 my $cmd = shift(@ARGV) or die;
@@ -68,7 +69,7 @@ for my $x (split(/,/, 'from-tag,to-tag,call-id,transport protocol,media address,
 for my $x (split(/,/, 'TOS,delete-delay')) {
 	defined($options{$x}) and $packet{$x} = $options{$x};
 }
-for my $x (split(/,/, 'trust address,symmetric,asymmetric,force,strict source,media handover,sip source address,reset,port latching,no rtcp attribute,loop protect,record call')) {
+for my $x (split(/,/, 'trust address,symmetric,asymmetric,force,strict source,media handover,sip source address,reset,port latching,no rtcp attribute,loop protect,record call,always transcode')) {
 	defined($options{$x}) and push(@{$packet{flags}}, $x);
 }
 for my $x (split(/,/, 'origin,session connection')) {