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Re: [webrtc-encoded-transform] Add API to request key frames (#125)

From: Bernard Aboba via GitHub <sysbot+gh@w3.org>
Date: Tue, 04 Jan 2022 00:03:15 +0000
To: public-webrtc-logs@w3.org
Message-ID: <issue_comment.created-1004436979-1641254594-sysbot+gh@w3.org>
@youennf @alvestrand Do we understand how we can ensure key synchronization when a new participant joins the conference?  In this situation, the sender may desire to generate a key frame and then apply a new encryption key (and keyId) to that keyframe. 

The updated key needs to be applied to the new keyframe, not to a previous or subsequent frame (which would lead to having the new participant being unable to decrypt and decode video until another keyframe update).

If a keyframe is encrypted using the old encryption key, then a newly joined receiver will not be able to decrypt it.  There are a number of ways in which the sender can generate a key frame and then ensure that a key update is applied to that newly generated key frame. The current PR does not make it clear how this would be achieved.

One way this might work is to have generateKeyFrame() return a timestamp which is then provided to setEncryptionKey().  It may also be possible to avoid a race condition without passing a timestamp.

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Please view or discuss this issue at https://github.com/w3c/webrtc-encoded-transform/pull/125#issuecomment-1004436979 using your GitHub account

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