Re: Video narration

[Paul Garlick]

Hi Laura and Ludo,

> the colours are changed. Ie: the dark gray turns
> green, and the white turns somewhat pink.

Commit 4bd2e78b893fef5ce1f12bec895ee8234cabaf1f fixes the colors. 
ffmpeg needed a different pixel format to set the chroma subsampling
correctly [1].

I have been able to play the newly built cli and nocli videos in
Firefox.  Also, the combined video now starts in Firefox but stops just
before the first transition.  I think the concatenation step in the
Makefile could be the cause.

Best regards,

Paul.

1. https://trac.ffmpeg.org/wiki/Encode/VP9