From a05f5052fef3b3743fab7846da12861d8a8098ec Mon Sep 17 00:00:00 2001
From: "Timothy B. Terriberry" <tterribe@xiph.org>
Date: Wed, 24 Sep 2014 17:43:22 -0700
Subject: [PATCH] sdp: Make opus declaration conform to the spec
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Signed-off-by: Martin Storsjö <martin@martin.st>
---
libavformat/sdp.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/libavformat/sdp.c b/libavformat/sdp.c
index 3c39ac7988c..eccd676f013 100644
--- a/libavformat/sdp.c
+++ b/libavformat/sdp.c
@@ -583,8 +583,18 @@ static char *sdp_write_media_attributes(char *buff, int size, AVCodecContext *c,
payload_type, c->sample_rate);
break;
case AV_CODEC_ID_OPUS:
- av_strlcatf(buff, size, "a=rtpmap:%d opus/48000\r\n",
+ /* The opus RTP draft says that all opus streams MUST be declared
+ as stereo, to avoid negotiation failures. The actual number of
+ channels can change on a packet-by-packet basis. The number of
+ channels a receiver prefers to receive or a sender plans to send
+ can be declared via fmtp parameters (both default to mono), but
+ receivers MUST be able to receive and process stereo packets. */
+ av_strlcatf(buff, size, "a=rtpmap:%d opus/48000/2\r\n",
payload_type);
+ if (c->channels == 2) {
+ av_strlcatf(buff, size, "a=fmtp:%d sprop-stereo:1\r\n",
+ payload_type);
+ }
break;
default:
/* Nothing special to do here... */
--
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