AtomicParsley

AtomicParsley is a lightweight command line program for reading, parsing and setting metadata into MPEG-4 files supporting the styles of metadata listed below.

One of its uses is that youtube-dl will look for this and if installed, uses it to embed thubnails into the files it downloaded.

• iTunes-style metadata into .mp4, .m4a, .m4p, .m4v, .m4b files
• 3gp-style assets (3GPP TS 26.444 version 6.4.0 Release 6 specification conforming) in 3GPP, 3GPP2, MobileMP4 & derivatives
• ISO copyright notices at movie & track level for MPEG-4 & derivative files
• uuid private user extension text & file embedding for MPEG-4 & derivative files

• original software: http://atomicparsley.sourceforge.net/
• maintainer's repo: https://github.com/wez/atomicparsley
• SFOS git repo: https://gitlab.com/nephros/openrepos-atomicparsley

There is a problem regarding youtube-dl, Google using webp instead of JPG on recent videos, and the fact that the installed ffmpeg package is missing the mjpeg2jpeg filter, which causes thumbnail embedding to not work sometimes. There is a version of youtube-dl here which tries to fix this problem.