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** THIS IS FIXED IN FROYO 2.2. **
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I started to report this against Froyo 2.2 but before submitting it, I used a tool that rebuilds the genre "database" on my Droid. Sure enough, after running the tool, everything was correct. I am still submitting this to the web site because I couldn't find this problem described anywhere. Hopefully, it will help those running older versions of Android.
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On my Motorola Droid, I've been using Meridian as my media player. It has the feature to play music by genre. All of my songs have correct genre information, except for my .m4a files. Those songs have the album title as their genre instead of the genre information displayed in iTunes or Mp3tag. I originally thought this was a problem with Meridian, but I recently installed the 3 (Cubed) media player. It has exactly the same problem. Since the 3 (Cubed) media player is open source, I went browsing through the source to see where the genre information comes from. Not being an Android developer myself, it appears that the genre information comes from MediaStore.Audio. That would explain why both players have the same incorrect information. Here is the body of the e-mail I sent to the Meridian developer that is my best guess as to why the genre information is incorrect for .m4a files.

Thanks, MikeP
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I have done some investigation about my problems with Genre handling in Meridian and it appears that Meridian does not handle the "gnre" tag in MP4 files the same way as most other apps in the world. This may be because iTunes does not follow the "official" standard and everyone has had to adapt their handling of the "gnre" tag to the way iTunes does it. For example, Mp3tag handles Genre's the same way as iTunes does for .m4a files. (According to the Atomic Parsley web site, the header of an MP4 file has some indicator of what "major file brand" the file conforms to. iTunes files have M4A in the header.)

If a song in iTunes has a Genre from the ID3v1 pre-defined list, see

http://www.id3.org/id3v2.3.0#head-129376727ebe5309c1de1888987d070288d7c7e7

it writes a "gnre" tag in a binary-encoded format where the binary value is one greater than the value listed on the web site. For example, the Genre "Rock" is written as a binary value of 18. (If the genre is outside that list, then iTunes uses the "gen" tag which contains the genre name in text.) Meridian's Genre handling expects that the "gnre" tag is followed by text and ends up using the title of the album as the Genre for the song for .m4a files ... because the album tag follows the Genre tag in most .m4a files in iTunes.

Two informative discussions on this topic can be found at:

http://www.hydrogenaudio.org/forums/lofiversion/index.php/t77947.html

and

http://forums.mp3tag.de/index.php?showtopic=10864&st=0&p=43095&#entry43095

I found these discussion threads by googling "gnre vs gen genre tags".

Hope this is information you may find useful,

MikeP

Issue 36920804

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