A while ago, I found out about the possibility to store Cover Art in FLAC files also
as a URL rather than to store the file itself. Further research showed that
it should be possible to use relative paths to files on the computer itself instead of a URL pointing to some web address.
Unfortunately it seems that there are very few entries on the Internet about doing that (I found only the one I linked to), so I cannot be 100% certain that I Did It Right, but I created a very small sample file to try this out (it would be nice if I could explicitly tell software to use image A as cover without having to attach the whole image to every file, especially with multiple files), and I failed.
What I did was to encode 5 seconds of silence to FLAC, then remove all metadata blocks (except StreamInfo), and use that file as a base.
I then created a Picture block with its MIME set to '-->' and its data portion (supposedly) pointing to 'Protected Memory/background.png' [I chose nonstandard names to avoid accidental detection]. I made sure that in the audio file's folder, a directory called 'Protected Memory' exists and that it contains a file called 'background.png', which is a valid PNG image. I used dimensions 0x0 which I believe* to have seen used as default for 'unknown' in some files.
I tried encoding the filepath directly from UTF-8 into binary format, as well as URL-escaping [transforming any special characters into the %xx versions] the path before conversion into binary format, but none of the two worked. (Admittedly, there is nothing to escape in the example path, but I was going to test Unicode next…)
I tried both normal playback in MC without importing the file, and importing the file into my library, but both showed no cover.
I realize that using picture blocks with URLs is discouraged, but I reason that this is due to the likelihood of 'accidental' Internet access to arbitrary sites, so I see little harm in using it to (in the end) store images used as Album Art only once rather than in each file.
Are URL-based Pictures not supported in MC? If so, is there a possibility to support them?
Or did I do something wrong?
I'll gladly help in any way I can, just let me know what to do, please!
* I
believe to have seen it because I don't remember which file(s) I've seen it use, and therefore can't just cough up samples. In fact, I'm reasonably certain, and could test this rather quickly if so requested.