# \[X\] MP3tag show no tags in M4A after tagging with TagLib **URL:** \ **Category:** No Bugs\ **Created:** [October 4, 2013, 6:59pm UTC](https://community.mp3tag.de/t/x-mp3tag-show-no-tags-in-m4a-after-tagging-with-taglib/15076 "2013-10-04T18:59:03Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![yindesu](https://community.mp3tag.de/letter_avatar_proxy/v4/letter/y/b77776/32.png) [@yindesu](https://community.mp3tag.de/u/yindesu)\ **Post date:** [October 4, 2013, 6:59pm UTC](https://community.mp3tag.de/t/x-mp3tag-show-no-tags-in-m4a-after-tagging-with-taglib/15076/1 "2013-10-04T18:59:03Z")
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). ---
**Author:** ![Florian](https://community.mp3tag.de/user_avatar/community.mp3tag.de/florian/32/5759_2.png) [@Florian](https://community.mp3tag.de/u/Florian)\ **Post date:** [October 4, 2013, 7:22pm UTC](https://community.mp3tag.de/t/x-mp3tag-show-no-tags-in-m4a-after-tagging-with-taglib/15076/2 "2013-10-04T19:22:20Z")
Sounds interesting 🙂 You can send a sample file to [support@mp3tag.de](mailto:support@mp3tag.de) ---
**Author:** ![yindesu](https://community.mp3tag.de/letter_avatar_proxy/v4/letter/y/b77776/32.png) [@yindesu](https://community.mp3tag.de/u/yindesu)\ **Post date:** [October 4, 2013, 8:08pm UTC](https://community.mp3tag.de/t/x-mp3tag-show-no-tags-in-m4a-after-tagging-with-taglib/15076/3 "2013-10-04T20:08:52Z")
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. ---
**Author:** ![Florian](https://community.mp3tag.de/user_avatar/community.mp3tag.de/florian/32/5759_2.png) [@Florian](https://community.mp3tag.de/u/Florian)\ **Post date:** [October 5, 2013, 7:58am UTC](https://community.mp3tag.de/t/x-mp3tag-show-no-tags-in-m4a-after-tagging-with-taglib/15076/4 "2013-10-05T07:58:23Z")
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 Florian ---
**Author:** ![yindesu](https://community.mp3tag.de/letter_avatar_proxy/v4/letter/y/b77776/32.png) [@yindesu](https://community.mp3tag.de/u/yindesu)\ **Post date:** [October 5, 2013, 6:09pm UTC](https://community.mp3tag.de/t/x-mp3tag-show-no-tags-in-m4a-after-tagging-with-taglib/15076/5 "2013-10-05T18:09:14Z")
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). ---
**Author:** ![Florian](https://community.mp3tag.de/user_avatar/community.mp3tag.de/florian/32/5759_2.png) [@Florian](https://community.mp3tag.de/u/Florian)\ **Post date:** [October 5, 2013, 6:45pm UTC](https://community.mp3tag.de/t/x-mp3tag-show-no-tags-in-m4a-after-tagging-with-taglib/15076/6 "2013-10-05T18:45:14Z")
> [@Florian](#): > > Are you one of the developers of TagLib or a contributor? If so, can you investigate this issue? ---
**Author:** ![yindesu](https://community.mp3tag.de/letter_avatar_proxy/v4/letter/y/b77776/32.png) [@yindesu](https://community.mp3tag.de/u/yindesu)\ **Post date:** [October 5, 2013, 6:53pm UTC](https://community.mp3tag.de/t/x-mp3tag-show-no-tags-in-m4a-after-tagging-with-taglib/15076/7 "2013-10-05T18:53:43Z")
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. ---
**Author:** ![Florian](https://community.mp3tag.de/user_avatar/community.mp3tag.de/florian/32/5759_2.png) [@Florian](https://community.mp3tag.de/u/Florian)\ **Post date:** [October 5, 2013, 8:20pm UTC](https://community.mp3tag.de/t/x-mp3tag-show-no-tags-in-m4a-after-tagging-with-taglib/15076/8 "2013-10-05T20:20:32Z")
OK. Thanks for reporting! Kind regards Florian ---
**Author:** ![Florian](https://community.mp3tag.de/user_avatar/community.mp3tag.de/florian/32/5759_2.png) [@Florian](https://community.mp3tag.de/u/Florian)\ **Post date:** [October 6, 2013, 8:28am UTC](https://community.mp3tag.de/t/x-mp3tag-show-no-tags-in-m4a-after-tagging-with-taglib/15076/9 "2013-10-06T08:28:50Z")
I've added a workaround for this with Mp3tag v2.58. ---
**Author:** ![Florian](https://community.mp3tag.de/user_avatar/community.mp3tag.de/florian/32/5759_2.png) [@Florian](https://community.mp3tag.de/u/Florian)\ **Post date:** [December 28, 2018, 2:33pm UTC](https://community.mp3tag.de/t/x-mp3tag-show-no-tags-in-m4a-after-tagging-with-taglib/15076/10 "2018-12-28T14:33:45Z")
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