here a wish,
The id3tag have no information place about the "rip source" (CD, flac, digital, radio, unknown), so i chose a way that fit me : use the covertart album resolution to define it.
All my perfect rip from my own CD, have a 1000x1000 pixels covertart
All my amazon purchases have a 900x900 pixels cover (i do)
all my radioFM rips are in 200x200 pixel
so, i need to search files by filtering on covertart resolution.
My daily need, is to find wish CD i need to buy, so have to search my old mp3 or radioFM one...
that is why, i need that kind of filter on the resolution of the coverART album.
Actually there is a tag-frame for that, Software Settings which can contain information about the used encoder.
This field is indexed in the database and can therefore be used in searches and such functions.