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Re: [webrtc-pc] Missing CNAME in RID based simulcast offer (#2114)

From: Iñaki Baz Castillo via GitHub <sysbot+gh@w3.org>
Date: Mon, 08 Jul 2019 14:45:41 +0000
To: public-webrtc-logs@w3.org
Message-ID: <issue_comment.created-509255793-1562597139-sysbot+gh@w3.org>
@alvestrand, the current status is:

* [Issue 10383: Simulcast video sends SDES with CNAME items with zero length](https://bugs.chromium.org/p/webrtc/issues/detail?id=10383) - Fixed.
* [Issue 10385: PeerConnection fails to match RTP streams if there is no a=ssrc line with CNAME attribute](https://bugs.chromium.org/p/webrtc/issues/detail?id=10385) - Not fixed.

This is: right now if Chrome generates a SDP without `a=ssrc:AAAAA cname:BBBBB`, such a SDP cannot be consumed by other Chrome.

One may argue: _SDP m= sections without `a=ssrc` lines just happen in RID based simulcast, which is not browser-to-browser._

Well, in theory and even without any kind of simulcast, the browser should be able to generate a SDP offer without any `a=ssrc` line in any m= audio or video section. In fact, `a=mid` is good enough (having both parties RTP MID support). **But** Chrome will fail to match incoming RTP due to lack of `a=ssrc:aaaaa cname:bbbb` lines.

Said that, IMHO this should be discussed in [Issue 10385: PeerConnection fails to match RTP streams if there is no a=ssrc line with CNAME attribute](https://bugs.chromium.org/p/webrtc/issues/detail?id=10385) rather than here.

-- 
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Received on Monday, 8 July 2019 14:45:43 UTC

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