- 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",