[SUGGESTION] FFMPEG's video capture feature support

[forart]

Hi there,
1st of all thanks for your valuable work as well as your listening to users' needs.

As already suggested to @cdgriffith in this FF's "issue", it would be extremely interesting to let Videomass use FFMPEG video capture feature as input too.

We've got inspired by @Jessecar96's git on How to capture, deinterlace, and encode analog video which proposes an interesting method on how to set FFMPEG for video capture through dedicated hardware.

If it helps to let you implement it easier, here are some simple FFMPEG capture scripts to get inspiration from:

• A collection of scripts to capture video with ffmpeg-python by @zfleeman
• FFMPEG scripts by @modeler
• FFMPEG-Capture by @pcntv

Hope that inspires !