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Re: [webrtc-pc] Using codecPayloadType with addTransceiver()

From: Bernard Aboba via GitHub <sysbot+gh@w3.org>
Date: Fri, 19 Oct 2018 16:17:49 +0000
To: public-webrtc-logs@w3.org
Message-ID: <issue_comment.created-431417979-1539965866-sysbot+gh@w3.org>
@Orphis addTransceiver sets the "simulcast envelope" (e.g. the number of encodings and their order) and it is prohibited to change this later with setParameters. Since the maximum number of encodings (and capabilities such as support for SVC) can vary by codec, it would make sense to specify the codecPayloadType in sendEncodings, if only to ensure that createOffer reflects the number of simulcast streams required with the desired codec.  For example, VP8/VP9/AV1 support temporal scalability and H.264/AVC does not, so that if it is desired to have 3 simulcast streams each with 3 temporal layers, this cannot be achieved with H.264/AVC.  Being able to determine this when addTransceiver is called is important so that action (such as trimming the number of simulcast streams or reporting on an unsupported scalabilityMode) can be taken immediately, rather than waiting until O/A completes and discovering that the encodings requested in addTransceiver() do not make sense.

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Received on Friday, 19 October 2018 16:17:54 UTC

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