External metadata storage tree for replaygain, mixramps, etc.

[GeorgA]

We use mpd for generating additional streams for a regular FM broadcaster. Currently the music data and the playlists are independent from the broadcast playout. So the music desk simply puts their files in appropriate directories on the stream system. We normalize them, generate the mixramps as ID3 and produce randomized playlists with some extra rules for rotatition, special schedules, etc. So the audio files for the streams are the modified "copies". That's Ok, as there are only a few 1000 files and this extra storage is not yet relevant.

For some special streams we now want to use the playlists "professionally" planned by Musicmaster based on the "official" audio database. This database is huge, so we do not want to use the same method and finally have a full copy just for the "mixramp"-ed files. Modification of the original playout files is a No-Go. For the playout normalization I can use ffmpeg-filters (with some issues not relevant here), but it seems there is currently no way to store mixramps independently from the audio file itself.

So my idea is to have a separate metadata-folder where metadata files are arranged like in the music-directory. With metadata_directory+song.GetURI() the corresponding metadata can be easily accessed (and also generated externally). The file then contains eg. XML and some tags like replaygain, mixramp_start/mixramp_end, etc. If there's such a file, the values are then submitted like in mpd_mpg123_id3v2_extras().

Does this sound reasonable and useful? Am I re-inventing something that is already there?

Georg