W3C home > Mailing lists > Public > public-webrtc@w3.org > December 2015

Re: Issue 412: Framerate knob for simulcast

From: Cullen Jennings <fluffy@iii.ca>
Date: Wed, 9 Dec 2015 10:27:51 -0700
Cc: Bernard Aboba <Bernard.Aboba@microsoft.com>, "public-webrtc@w3.org" <public-webrtc@w3.org>
Message-Id: <DF574190-456A-4A58-841B-98961AECCC9E@iii.ca>
To: Martin Thomson <martin.thomson@gmail.com>

> On Dec 8, 2015, at 6:00 PM, Martin Thomson <martin.thomson@gmail.com> wrote:
> I'm more concerned about how an implementation might meet this limit.
> For instance, if I have a 30 frame per second source and this is set
> to 25, what would you expect to happen?

Some video encoders use the motion compensation in the video compression to interpolate virtual intermediate frames so they can produce 25, some implementations would just drop to 15 fps. Implementations can decide and it may depend on the codec, if they are using hardware, amount of CPU available etc. 

Oh and some sort of broken implementation will produce 25 fps by using an algorithm where each time they need to form an output frame, they just use the most recent input frame - that will make from visual jitter in the motion but more than one crappy product has shipped that. 
Received on Wednesday, 9 December 2015 17:28:18 UTC

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