Converting webm blob

Hi,

this is more of a question than a feature request,

I use capturestream() to currently record canvas animations (1660 x 960) and output to a webm blob then download

The downloaded file is not 100% perfect.

On the latest firefox build the video is perfect., However with chromium browsers there are issues with the way the webm is created. First one is the seekable usse ( which we can fix, however it causes an error in the player when you actually use the seek feature)

Can ffmpeg.wasm be used to fix the webm and output it? because after testing the mp4 conversion with a resolution of 1660 x 960 the conversion takes far to long.

webm on the other hand is really fast compared.