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Re: [webrtc-pc] Handling of simulcast errors

From: Taylor Brandstetter via GitHub <sysbot+gh@w3.org>
Date: Thu, 26 Jan 2017 21:04:19 +0000
To: public-webrtc-logs@w3.org
Message-ID: <issue_comment.created-275513090-1485464657-sysbot+gh@w3.org>
`setParameters()` can't change the number of layers, but it could 
activate layers that are inactive. If we assume a browser may have 
codec-specific restrictions, then consider this example:

1. `addTransceiver` called with 5 layers.
2. `createOffer` called. Suppose the offer contains one codec that 
supports all 5 layers, one that supports 3 layers, and another that 
doesn't support simulcast.
3. Offer/answer negotiation resulted in the last codec being chosen.
4. `sender.getParameters` should return 5 encodings, but 4 of them are
 not active (`active == false`). (Is this correct?)
5. If the application wants to switch to the codec that supports 
simulcast, it can set the `active` flag to true and reorder the 
codecs, then call `sender.setParameters`.
6. If more encodings were activated than are supported for the new 
codec, the promise needs to be rejected with an error.

So, I like Bernard's idea of having 
`RTCRtpCodecCapability.maxSimulcastStreams`. Doesn't ORTC already have
 this, with `maxTemporalLayers` and `maxSpatialLayers`?

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Received on Thursday, 26 January 2017 21:04:54 UTC

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