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From: Dave Taht <>
To: Juliusz Chroboczek <>
Subject: [Galene] Re: SVC support
Date: Wed, 12 May 2021 08:41:15 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Wed, May 12, 2021 at 8:19 AM Juliusz Chroboczek <> wrote:
> Hi,
> I've just pushed the code for Scalable Video Coding (SVC) to the branch
> "svc" of the github repository; be aware that I will be rebasing this
> branch.  It's currently running on port 8444 (but not port
> 8443, which is running stable 0.3.5).
> SVC is a technique where a single video stream is "layered": frames are
> labelled with information about whether they can be dropped, and the
> server can reduce the bitrate sent to a client.  The advantage of SVC over
> simulcast is that switching layers is a much more lightweight operation:
> switching simulcast streams requires a keyframe, while switching scalable
> layers can happen a few times per packet.

This is a really, really promising sounding technique!

> SVC requires no support on the receiver side -- it's the sender who does
> the layering, the receiver receives a perfectly banal video stream.
> Sending a scalable stream is controlled by the simulcast switch, due to
> some limitations in both Chrome/Chromium and Firefox, so you cannot have
> SVC without simulcast.  Which is a waste, but what can I do.

Currently. As both these are open source they can certainly be
improved. I haven't
hacked on firefox in quite some time... I can reach out to some contacts in the
mozilla organization and/or is there a good mailing list to join?

> You can test by enabling simulcast then testing the "stats.html" page; the
> layer chosen for each down track is indicated before the bitrate.
> Temporal scalability (reducing the framerate) is supported for both VP8
> and VP9; unfortunately, I wasn't able to test the VP9 support, since my
> version of Chromium immediately crashes when you request a VP9 simulcast
> stream.  Spacial scalability (reducing the resolution) should be doable
> for VP9, but the point is somewhat moot until Chromium fix their bug.

Have you reported it?

> -- Juliusz
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Dave Täht CTO, TekLibre, LLC

  reply	other threads:[~2021-05-12 15:41 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-12 15:19 [Galene] " Juliusz Chroboczek
2021-05-12 15:41 ` Dave Taht [this message]
2021-05-12 16:26   ` [Galene] " Juliusz Chroboczek
2021-05-12 16:35     ` Juliusz Chroboczek

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