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From: Guillaume Denis <>
To: Juliusz Chroboczek <>
Subject: [Galene] Re: about packet pacers
Date: Tue, 10 Aug 2021 10:10:20 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

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Toke, Juliusz, thanks for your input.

As a followup and even if it's off topic for Galene users I'll share this
implementation of the GCC algorithm based on RTCP packets:
(with a resulting periodical update of GStreamer encoder bitrates)

Using pacers is a bit too networky for me right now, I'll see how much I
need it.
Thanks, Guillaume

Le sam. 7 août 2021 à 01:01, Juliusz Chroboczek <> a écrit :

> >> Toke, would you have some input regarding this:
> >> - do you think that in this use case monitoring a pacer with the target
> >> bitrate would have real added value?
> > Hmm, so the idea here would be that we know the bitrate of the stream
> > from the codec setting, and from that we can compute the packet-level
> > bitrate (by adding the packet overhead) and pace out the packets at that
> > rate? [...]
> > One question is whether the codec can be relied upon to stay within a
> > certain bitrate and over what timescales?
> No, but we know where the current frame ends, and we know when the next
> frame is due.  So we can spread the current frame smoothly over the
> interval between the current frame and the next one.  That will break when
> we get variable frame-rate codecs, but we'll cross that bridge when we get
> there.
> This is not what the GCC draft recommends[1]: what they suggest is to
> consider the target bitrate (the one that the congestion controller yields)
> and send a burst of up to 5ms*rate every 5ms.
> [1]
> > On Linux you can use the SO_TXTIME socket option to get the kernel to
> > pace the packets for you; but that only works if there's a qdisc
> > installed that can handle the pacing (such as sch_fq), and it's hardly
> > cross-platform, so dunno if that will work?
> I'd rather we did the pacing in the application, since that will allow us
> to drop packets more selectively: if we drop a packet due to congestion
> control, then we want to continue dropping until the end of the frame.
> What's more, both the VP8 and VP9 codecs can be configured in a mode where
> they regularly schedule a "droppable" frame that is not used for
> intra-prediction (it's part of the simulcast implementation).
> -- Juliusz

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  reply	other threads:[~2021-08-10  8:10 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-06 12:11 [Galene] " Guillaume Denis
2021-08-06 13:42 ` [Galene] " Juliusz Chroboczek
2021-08-06 20:34 ` Toke Høiland-Jørgensen
2021-08-06 23:01   ` Juliusz Chroboczek
2021-08-10  8:10     ` Guillaume Denis [this message]
2021-08-18 18:43       ` Juliusz Chroboczek
2021-08-18 21:32         ` Juliusz Chroboczek
2021-08-19  9:25           ` Guillaume Denis
2021-08-19 11:10             ` Juliusz Chroboczek
2021-09-28 20:51     ` Dave Taht

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