Improve videos encoding quality and size

[edouard-lopez]

Not sure that the right place to put it, feel free to copy/paste.

Comparison

Videos uploaded by Lingua Libre are approximately 5-10 times larger than the one I extracted and encoded from Laura Jauvert video (for the same duration and with a lower resolution).

Source	Example	Duration	Resolution	Size (Kb)
Lingua Libre	LL-Q33302 (fsl)-Taliba31-comédien.webm	2.0 s	640 × 480	622 KB
LSF-data	Adolescent.webm	2.0 s	1,280 × 720	123 KB

Increase Quality

When I worked on the project I played a bit with FFMPEG options to get video as light and sharp as possible, i.e. with minimal blur on movement and small size as I targeted mobile usage.

My encoding script used the libvpx-vp9 codec and a bunch of other option for mobile (640x480) and desktop (1280x720).

Hope this could help

[hugolpz]

We are recording with vp9 too so this is a bit weird :

mimeType = 'video/webm;codecs="vp9,opus"';

[edouard-lopez]

With what options? Default are not great, but the VP9 doc is really well done