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Re: [mediacapture-record] Input video track width and height MUST be recorded and playable (#173)

From: guest271314 via GitHub <sysbot+gh@w3.org>
Date: Sun, 01 Sep 2019 03:26:36 +0000
To: public-webrtc-logs@w3.org
Message-ID: <issue_comment.created-526882648-1567308395-sysbot+gh@w3.org>
@alvestrand Had concluded that Chromium implementation of HTML `<video>` element was the reason that variable frame width and height was not displayed at resulting WebM file output by `MediaRecorder`, given this code https://github.com/guest271314/MediaFragmentRecorder/blob/imagecapture-audiocontext-readablestream-writablestream/MediaFragmentRecorder.html displays only the initial width and height of the first frame or track width and height at Chromium, though the WebM file does display variable width and height at Mozilla Firefox and Nightly.

This code https://plnkr.co/edit/4JxS4O?p=preview demonstrates that the options set for VP8 and VP9 codecs at Chromium could be the issue, using https://github.com/thenickdude/webm-writer-js with the minimal amount of lines commented from the original repository to output variable width and height and dispatches `resize` event at HTML `<video>` element (though not sure yet how to set the correct frame rate using that repository). 

`MediaRecorder` outputs a WebM video which for an unknown reason is constant width and height set at the initial frame or track.

There are use cases for both constant pixel dimensions and variable pixel dimensions. In this case the expected output is variable width and height (the same as input) which should cause HTML `<video>` element to dispatch `resize` event when the resolution changes. That is what the linked PR https://github.com/w3c/mediacapture-record/pull/172 changes about this specification: the capability to set constant or variable pixel dimensions for the WebM file output, which has consistent display properties at both Mozilla Firefox and Nightly and Chromium and Chrome browsers, et. al.



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Received on Sunday, 1 September 2019 03:26:38 UTC

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