Writing ID3v2.2 tag writes album image as APIC frame rather than PIC

[joshuamaciak]

Hi, I've stumbled upon what I think is a bug in mp3agic.

While testing my own (very buggy) album art puller, I noticed what appears to be an issue with saving an mp3 with id3v2.2 frames. To reproduce, simply open an mp3, set an id3v2.2 tag, and save the mp3. As so:

Mp3File mp3 = new Mp3File("notags.mp3"); 
ID3v22Tag tag = new ID3v22Tag();
byte[] albumArt = Files.readAllBytes(new File("image.png").toPath());
tag.setAlbumImage(albumArt, "image/png");
mp3.setId3v2Tag(tag);
mp3.save("id3v22.mp3");

I've used the notags.mp3 & image.png from the test resources so it is more easily reproducible.

Opening up the id3v22.mp3 in a hex editor shows the following

49443302 00000000 0E744150 4943

Translated:

ID3 version 2 (as expected) ... APIC

According to the ID3v2 spec:

Attached picture   "PIC"
Frame size         $xx xx xx
Text encoding      $xx
Image format       $xx xx xx
Picture type       $xx
Description        <textstring> $00 (00)
Picture data       <binary data>

The APIC frame did not exist until ID3v2.3, so trying to parse the frame as a true PIC frame fails as the frame layout is slightly different.
I was able to trace this back to AbstractID3v2Tag.java in the packFrames(...) method where it packs the frame as APIC regardless of the ID3v2 version.

int newOffset = packSpecifiedFrames(bytes, offset, null, "APIC");
newOffset = packSpecifiedFrames(bytes, newOffset, "APIC", null);
return newOffset;

The way I'd fix it is maybe overriding the one of the 'pack' methods in each ID3v2#Tag class. This way we could pack the corresponding frames in the appropriate way in each version. At a glance, it seems like a quite few of the frames changed between 2.2 & 2.3, so this is pretty significant.

BTW, thanks a lot for this library. I use it quite a lot for an android app I'm developing.

EDIT: after working through this I saw in the README that mp3agic doesn't support writing id3v2.2 tags. However, I feel this is still an issue as the new mp3 saves successfully & still reports v2.2 tags in the outputted mp3.