From f2d7372f5a6950c1e696c9f6755e7e89961bfdfe Mon Sep 17 00:00:00 2001
From: Richard Fuchs <rfuchs@sipwise.com>
Date: Wed, 23 Jun 2021 14:27:33 -0400
Subject: [PATCH] TT#14008 fix transcoding logic

Transcoding should not be decided based on the name of the codec alone,
but primarily on the payload type. First the PT needs to be compared,
then the codec type must be confirmed.

closes #1289

Change-Id: I1a8bffc6d521443aba14d9b4cf1ad4d1e21f1226
---
 daemon/codec.c | 94 ++++++++++++++++++++------------------------------
 1 file changed, 38 insertions(+), 56 deletions(-)

diff --git a/daemon/codec.c b/daemon/codec.c
index b26ccfd04..8a867920e 100644
--- a/daemon/codec.c
+++ b/daemon/codec.c
@@ -1454,13 +1454,12 @@ void codec_handlers_update(struct call_media *receiver, struct call_media *sink,
 				receiver_transcoding,
 				transcode_supplemental, pcm_dtmf_detect);
 
-		struct rtp_payload_type *dest_pt; // transcode to this
+		struct rtp_payload_type *dest_pt = NULL; // transcode to this
 
-		GQueue *dest_codecs = NULL;
 		if (pref_dest_codec->for_transcoding) {
 			// with force accepted codec, we still accept DTMF payloads if possible
 			if (pt->codec_def && pt->codec_def->supplemental)
-				dest_codecs = g_hash_table_lookup(sink->codec_names_send, &pt->encoding);
+				dest_pt = g_hash_table_lookup(sink->codecs_send, GINT_TO_POINTER(pt->payload_type));
 		}
 		else {
 			// we ignore output codec matches if we must transcode supp codecs
@@ -1471,59 +1470,42 @@ void codec_handlers_update(struct call_media *receiver, struct call_media *sink,
 			else if (pcm_dtmf_detect)
 				;
 			else
-				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;
-			for (GList *k = dest_codecs->head; k; k = k->next) {
-				unsigned int dest_ptype = GPOINTER_TO_UINT(k->data);
-				dest_pt = g_hash_table_lookup(sink->codecs_send, GINT_TO_POINTER(dest_ptype));
-				if (!dest_pt)
-					continue;
-				if (dest_pt->clock_rate != pt->clock_rate ||
-						dest_pt->channels != pt->channels) {
-					dest_pt = NULL;
-					continue;
-				}
-				break;
-			}
-
-			if (!dest_pt)
-				goto unsupported;
-
-			// in case of ptime mismatch, we transcode, but between the same codecs
-			if (dest_pt->ptime && pt->ptime
-					&& dest_pt->ptime != pt->ptime)
-			{
-				ilogs(codec, LOG_DEBUG, "Mismatched ptime between source and sink (%i <> %i), "
-						"enabling transcoding",
-					dest_pt->ptime, pt->ptime);
-				goto transcode;
-			}
-
-			if (flags && flags->inject_dtmf) {
-				// we have a matching output codec, but we were told that we might
-				// want to inject DTMF, so we must still go through our transcoding
-				// engine, despite input and output codecs being the same.
-				goto transcode;
-			}
-
-			// XXX needs more intelligent fmtp matching
-			if (rtp_payload_type_cmp_nf(pt, dest_pt))
-				goto transcode;
-
-			// do we need silence detection?
-			if (cn_pt_match == 2 && MEDIA_ISSET(sink, TRANSCODE))
-				goto transcode;
-
-			// XXX check format parameters as well
-			ilogs(codec, LOG_DEBUG, "Sink supports codec " STR_FORMAT, STR_FMT(&pt->encoding_with_params));
-			__make_passthrough_gsl(handler, &passthrough_handlers);
-			if (pt->codec_def && pt->codec_def->dtmf)
-				__dtmf_dsp_shutdown(sink, pt->payload_type);
-			goto next;
-		}
+				dest_pt = g_hash_table_lookup(sink->codecs_send, GINT_TO_POINTER(pt->payload_type));
+		}
+		if (!dest_pt)
+			goto unsupported;
+
+		// in case of ptime mismatch, we transcode, but between the same codecs
+		if (dest_pt->ptime && pt->ptime
+				&& dest_pt->ptime != pt->ptime)
+		{
+			ilogs(codec, LOG_DEBUG, "Mismatched ptime between source and sink (%i <> %i), "
+					"enabling transcoding",
+				dest_pt->ptime, pt->ptime);
+			goto transcode;
+		}
+
+		if (flags && flags->inject_dtmf) {
+			// we have a matching output codec, but we were told that we might
+			// want to inject DTMF, so we must still go through our transcoding
+			// engine, despite input and output codecs being the same.
+			goto transcode;
+		}
+
+		// XXX needs more intelligent fmtp matching
+		if (rtp_payload_type_cmp_nf(pt, dest_pt))
+			goto transcode;
+
+		// do we need silence detection?
+		if (cn_pt_match == 2 && MEDIA_ISSET(sink, TRANSCODE))
+			goto transcode;
+
+		// XXX check format parameters as well
+		ilogs(codec, LOG_DEBUG, "Sink supports codec " STR_FORMAT, STR_FMT(&pt->encoding_with_params));
+		__make_passthrough_gsl(handler, &passthrough_handlers);
+		if (pt->codec_def && pt->codec_def->dtmf)
+			__dtmf_dsp_shutdown(sink, pt->payload_type);
+		goto next;
 
 unsupported:
 		// the sink does not support this codec -> transcode