[X] MP3tag show no tags in M4A after tagging with TagLib

I believe I found a similar bug. After saving a new Comment field with TagLib, Mp3tag no longer detects an MP4 tag in my file. iTunes and foobar2000 (and TagLib) can still read the file.

Looking in the file with a hex editor, it appears the tag data is all still there, so it seems Mp3tag is breaking where no other major player is, when attempting to read an MP4 tag.

I can send a sample file (before and after) to the developers (Florian or someone else?) if needed. This also affected Mp3tag 2.55a (I'm now using 2.57 which also can't find the MP4 tag).

Sounds interesting :slight_smile: You can send a sample file to support@mp3tag.de

I sent the 2 files by sendspace. Let me know if that's a problem and I should attach them (6 MB each) or use a different website.

Thanks for the example files.

I had a look at them and it seems that the size from the atom header is invalid for the after.m4a file. You can easily validate this by looking at those numbers:

Total file size 6658750
Atom ftyp @ 0 of size: 24, ends @ 24
Atom moov @ 24 of size: 50624, ends @ 50648
Atom free @ 50648 of size: 4096, ends @ 54744
Atom mdat @ 54744 of size: 6604298, ends @ 6659042

You can see that the mdat atom exceeds the total file size.

Are you one of the developers of TagLib or a contributor? If so, can you investigate this issue?

Kind regards

Yikes, I should have tried playing the files. foobar2000 and iTunes stop playing the file 2 seconds early.

I guess it's interesting that most major software still reads the tags though (even Windows Explorer does).

I haven't contributed very much, just reported several issues since I am intending to use the library for an Android project.

Since my last post I was investigating, but it took longer than I wanted... and I can't reproduce. I managed to only create correct files, when compared with the original "after.m4a" with HxD hex editor, I got "the chosen files are identical. the file sizes are different, though!" Windows says the "size on disk" is identical (6,660,096 bytes) but the "size" differs (6,658,750 vs 6,659,042).

I filed a report on GitHub but since I can't reproduce I don't know what to expect.

OK. Thanks for reporting!

Kind regards

I've added a workaround for this with Mp3tag v2.58.

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