[ortc] RTX and ssrc indication

ibc has just created a new issue for https://github.com/openpeer/ortc:

== RTX and ssrc indication ==
According to the spec:

> 9.12.1 Dictionary RTCRtpRtxParameters Members
payloadType of type payloadtype
The payload type to use for retransmission. If unset, 
RTCRtpCodecParameters.payloadType for the "rtx" codec is used by 
ssrc of type unsigned long
The SSRC to use for retransmission, as specified in [RFC4588]. If 
unset when passed to RTCRtpSender.send(), the browser will choose.

When it comes to SDP, how is such a SSRC indicated? For example (some 
stuff removed):

m=video 62125 UDP/TLS/RTP/SAVPF 100 101 116 117 96
a=rtpmap:100 VP8/90000
a=rtcp-fb:100 ccm fir
a=rtcp-fb:100 nack
a=rtcp-fb:100 nack pli
a=rtcp-fb:100 goog-remb
a=rtpmap:101 VP9/90000
a=rtcp-fb:101 ccm fir
a=rtcp-fb:101 nack
a=rtcp-fb:101 nack pli
a=rtcp-fb:101 goog-remb
a=rtpmap:116 red/90000
a=rtpmap:117 ulpfec/90000
a=rtpmap:96 rtx/90000
a=fmtp:96 apt=100
a=ssrc-group:FID 2370134951 1456621734
a=ssrc:2370134951 cname:KZloQhO7d7spe7DA
a=ssrc:2370134951 msid:f2ZAO9Z0CX2iYNdVD4EMZ7vr5gGxUQugpRkz 
a=ssrc:2370134951 mslabel:f2ZAO9Z0CX2iYNdVD4EMZ7vr5gGxUQugpRkz
a=ssrc:2370134951 label:37d3d6c3-7646-48aa-bdc1-59fa55118a14
a=ssrc:1456621734 cname:KZloQhO7d7spe7DA
a=ssrc:1456621734 msid:f2ZAO9Z0CX2iYNdVD4EMZ7vr5gGxUQugpRkz 
a=ssrc:1456621734 mslabel:f2ZAO9Z0CX2iYNdVD4EMZ7vr5gGxUQugpRkz
a=ssrc:1456621734 label:37d3d6c3-7646-48aa-bdc1-59fa55118a14

It indicates that the `RtpSender` can send RTX packets with payload 
`96` for codec VP8 (payload `100`). Since `ssrc-group` is used, should
 I understand that RTX packets for VP8 will be sent with ssrc 

Please view or discuss this issue at 
https://github.com/openpeer/ortc/issues/386 using your GitHub account

Received on Monday, 29 February 2016 10:29:25 UTC