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Re: [mediacapture-record] Add keyframe interval support. (#216)

From: Andreas Pehrson via GitHub <sysbot+gh@w3.org>
Date: Fri, 03 Feb 2023 12:24:44 +0000
To: public-webrtc-logs@w3.org
Message-ID: <issue_comment.created-1415802940-1675427081-sysbot+gh@w3.org>
> Is there an example of an encoder where per-frame control of keyframes isn't possible?

Is there a risk with the per-frame API for keyframes, that the encoded stream has more visual artifacts as a result of the encoder having a harder time predicting how to allocate the target bitrate, than if it were to configure the encoder with a per-frame interval?

I have seen behavior in libvpx suggesting this, but I'm not sure how much of it was due to using VPX_EFLAG_FORCE_KF and how much was due to a [libvpx bug](https://bugs.chromium.org/p/webm/issues/detail?id=1714).

IIRC Firefox sets a keyframe interval of 10 seconds, for historical reasons [1], and occasionally recalculates the frame-interval based on recent incoming framerate, so it can configure the encoder with this.

[1] our ebml writer only creates a new cluster on a keyframe, and the max timestamp within a cluster is 32 seconds.

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