The audio in the MP4 is likely of similar quality to the M4A. It’s the video in the MP4 that is adding to the file size.
Oops, M4a is not a vidéo format !
Ok it works, Free YouTube to MP3 Converter keeps the album art, plus the good quality. Very well.
Until now I don’t manage to extract and put again this image with Mp3Tag, but maybe later I will…
I do soon the summary