[webrtc-pc] Is "same PT, different FMTP lines" allowed in BUNDLE? (#2766)

henbos has just created a new issue for https://github.com/w3c/webrtc-pc:

== Is "same PT, different FMTP lines" allowed in BUNDLE? ==
While working on https://github.com/w3c/webrtc-stats/issues/662#issuecomment-1232989049, we discovered that Chrome is able to handle a BUNDLEd transport where different m= sections use the same codec and payload type but where the FMTP line is different. See [fiddle](https://jsfiddle.net/henbos/7kqxgnr8/) (you'd think this would throw, but it doesn't).

The idea that it should be possible to have different FMTP lines for the same PT and transport was expressed by @jan-ivar [here](https://github.com/w3c/webrtc-stats/issues/614#issue-1108790558) and @taylor-b [here](https://webrtc-review.googlesource.com/c/src/+/273707), while @fippo strongly believes that this should be illegal and there is a bug in Chrome.

I don't know what BUNDLE says but different FMTP lines sounds wrong to me. What should be the correct behavior? (If it is not, some recent code to avoid duplicate RTCCodecStats objects in libwebrtc could be simplified.)

Please view or discuss this issue at https://github.com/w3c/webrtc-pc/issues/2766 using your GitHub account

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Received on Friday, 2 September 2022 11:28:07 UTC