Ah, old MP3 players of course can be quite picky regarding metadata as well, not just supported file formats.

I ended up having to do two things for the files in the final mix, strip ogg metadata and rewrite it only with the most basic info like artist, title, etc, and then for mp3 files, I had to get rid of ID3v2.4 info and replace it with ID3v2.3. With these fixes my old iaudio player can display the info correctly and play the files without choking.

Script updated, with some extra info on how I did it

https://git.bleu255.com/comfy/file/comfybin/mixtape.html

#mp3 #ogg #ffmpeg #id3v2 #shell #script

The #ID3v1 tag occupies 128 bytes, beginning with the string TAG 128 bytes from the end of the file.

The #ID3v2 tags are of variable size, and usually occur at the start of the file, which aids streaming media.

A #cover #artwork would be in the later format, so that after truncating the beginning of the file to the announced size, the remaining end of the file match the torrent pieces:
• https://pastebin.com/p4mPWNmF (PHP)
• https://pastebin.com/Y67UW7KA (Python)