Remove [FFmpeg] scene detection filter [to make thumbnail/cover/poster creation more reliable]

[deldesir]

Makes the video cover generation upon upload failsafe for some videos with little scene changes.

Tested on Ubuntu 24.04 (LRN2)

Fixes #214

[holta]

Great!

@deldesir or any FFmpeg wizards should feel free to add more elegant thumbnails/covers/posters at a later date, if this is failsafe!

[holta]

@deldesir should the "apply filters to avoid black frames and scale" comment be slightly revised, e.g. if black / background frames are no longer being avoided?

calibre-web/cps/uploader.py

Line 327 in 6ba8be7

'-vf', 'fps=1,thumbnail,scale=-1:720', # apply filters to avoid black frames and scale

[deldesir]

You're right, It's not accurate anymore. Done in #226