use webm-writer with mediarecorder

[millzee01]

Hi,

Can webm-writer be used to create the final webm output from a mediarecorder blob?

the reason i ask is because chromium browsers don't seem to write the final segment size as its used to stream (hens no final size)

Which causes a playback problem on standard players.

I believe web-writer resolves this issue, but wonder if I can use it like this?

[guest271314]

You can utilize ts-ebml, e.g., see guest271314/MediaFragmentRecorder#8 (comment).

[bevand10]

https://w3c.github.io/webcodecs/samples/capture-to-file/capture-to-file.html

[guest271314]

@bevand10 The resulting .webm files has issues: No frames appear to be written. Are you sure WebCodecs implementation of VP8 and VP9 are consistent with what is expected per Matroska specification?

The WebCodecs 'opus' implementation is not consistent with Opus implementation of MediaRecorder. AFAICT there is no way to playback the 'opus' encoded frames without using WebCodecs implementation to decode. Even then there are issues with regard to integration with MediaStreamTrackGenerator, see

• https://bugs.chromium.org/p/chromium/issues/detail?id=1180089
• https://bugs.chromium.org/p/chromium/issues/detail?id=1184070
• Add "real-time" warning/note to VideoTrackGenerator w3c/mediacapture-transform#20
• https://bugs.chromium.org/p/chromium/issues/detail?id=1199377