There is no muxId in RTCRtpEncodingParameters #528

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ibc opened this Issue May 2, 2016 · 4 comments

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@ibc
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ibc commented May 2, 2016 edited

In http://ortc.org/wp-content/uploads/2016/03/ortc.html#idl-def-RTCRtpParameters:

muxId of type DOMString, defaulting to ""

[...] Note that including muxId in RTCRtpParameters rather than in RTCRtpEncodingParameters implies that if it is desired to send simulcast streams with different muxId values for each stream, then multiple RTCRtpSender objects are needed.

But I cannot find muxId within RTCRtpEncodingParameters... May be it means the encodingId field, but that is related to the RID header extension which, AFAIK, it's not the same as the MID header extension.

@aboba
Contributor
aboba commented May 2, 2016

In ORTC, the equivalent of RTCRtpEncodingParameters.rid in WebRTC 1.0 is
RTCRtpEncodingParameters.encodingId.

In ORTC the equivalent of RTCRtpTransceiver.mid in WebRTC 1.0 is RTCRtpParameters.muxId.

In both ORTC and WebRTC 1.0, there only a single muxId/mid per receiver or sender.

@ibc
Contributor
ibc commented May 2, 2016

Thanks, but I still consider that the spec is wrong as it clearly says "Note that including muxId in RTCRtpParameters rather than in RTCRtpEncodingParameters", but it is clear that there is no muxId in RTCRtpEncodingParameters.

I would replace the above quoted text with:

When it comes to simulcast, including muxId in RTCRtpParameters rather than different encodingId in RTCRtpEncodingParameters implies that multiple RTCRtpSender objects with different muxId are needed.

@aboba
Contributor
aboba commented May 4, 2016

In addition to a change to the referred to text, a note in the WebRTC compatibility section appears needed.

@aboba aboba added a commit that referenced this issue May 4, 2016
@aboba aboba There is no muxId in RTCRtpEncodingParameters
Fix for Issue #528
857fe3c
@aboba aboba added the PR exists label May 4, 2016
@ibc
Contributor
ibc commented May 4, 2016

if it is desired to send simulcast streams with different muxId values for each stream, then multiple RTCRtpSender objects are needed.

I assume that a ORTC browser cannot receive simulcast in this fashion (it would require multiple RtpReceivers so multiple generated MediaStreamTracks). Am I right?

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