5 comments on “Chrome’s WebRTC VP9 SVC Layer Cake: Sergio Garcia Murillo & Gustavo Garcia

  1. Hi Sergio. Fantastic blogpost! Now both Firefox and Chrome seem to support SVC by default which makes me wonder about this:

    > Provide a way to enable or disable SVC in a per session basis, so you can have a multiparty call with SVC and a 1:1 call using traditional VP9 to avoid the overhead of SVC encoding.

    We are exactly in this situation and I can’t find a way to disable SVC. Any ideas of how to do it?

  2. Pingback: H.264 finally a first class citizen in #WebRTC stacks. | WebRTC by Dr Alex

  3. The post says:

    “To upscale temporally the SFU should have to wait for a layer frame with the switching point flag (Ubit set to 1) enabled.”

    However the definition of flag U is:

    “U: Switching up point, which specifies if the current layer frame depends on previous layer frames of the same temporal layer.”

    So shouldn’t the SFU wait for a frame with U set to 0?

    Also, after flags definition (P, D and U flags) the text says:

    “It is possible to up-switch up to a higher temporal layer on a layer frame which S bit is set to 0, as subsequent higher temporal layer frames will not depend on any previous layer frame from a temporal layer higher than the current one. ”

    No idea what the “S bit” is. Should it be “U flag” instead?

  4. Yes, seems an editorial typo, the info is correct on the upscale section:

    “To upscale temporally the SFU should have to wait for a layer frame with the switching point flag (U bit set to 1) enabled. ”

    U: 1 -> frame does not depend on previous layer frames of same temporal layer, so upswitch is possible

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