どうやらffmpeg単体ではできなさそう
#4448 (Support writing album cover art image embedded in ogg / opus metadata) – FFmpeg
trac.ffmpeg.org
なので、
METADATA_BLOCK_PICTUREタグにbase64化したカバーアートを自力で埋め込む必要があるっぽい。どうやらflacと同じ形式(というかflacから持ってきた？)みたい
node.jsで使う
恐らく下のライブラリを使えばできそう?
@hiogawa/flac-picture
encode an image file (jpg, png) to embed it as a cover art of an audio file (vorbis, opus, flac).. Latest version: 1.0.0-pre.5, last published: 2 years ago. Start using @hiogawa/flac-picture in your project by running `npm i @hiogawa/flac-picture`. There are no other projects in the npm registry using @hiogawa/flac-picture.
www.npmjs.com
参考
VorbisComment - XiphWiki
wiki.xiph.org
Adding album art to ogg files from the command line - Alex Cabal
alexcabal.com