[ID3 Dev] Re: Apple iTunes complicance issues

Florian Heidenreich support at mp3tag.de
Thu Feb 22 04:57:17 PST 2007

Nathan Hjelm wrote:
> Jud White <jwhite <at> cdtag.com> writes:
>> Please correct me if I'm wrong... do you have to purchase a membership 
>> to report a bug?
>> I have a few things to report:
>> 1. In ID3v2.4, non-syncsafe sizes are written to frames (ie, bit 7 is 
>> used).  The spec has changed in regards to how frame sizes are written 
>> from ID3v2.3 to ID3v2.4.  Also, iTunes does not read frames written with 
>> syncsafe sizes correctly.  See http://id3.org/id3v2.4.0-structure, 
>> section 4, paragraph 3.  Frame sizes should be written the same way as 
>> the total tag size is written in the header in ID3v2.4.  Also, it's easy 
>> enough to determine which size-encoding method was used by attempting to 
>> seek to the next position and testing for a valid frame signature/end of 
>> tag; in other words, it's not too late to correct this behavior.
> I have noticed a non-compliance in other frames as well. More specifically,
> iTunes does not use synchsafe integers in any of these frames (and probably
> others): "APIC", "COMM", "COM ", and "GEOB". It doesn't surprise me Apple has
> not fixed the issue as they are very slow at fixing bugs that don't affect a
> large number of users.

I've also noticed the bugs in iTunes (as many users of my tagger did).

Another funny thing is the the way iTunes stores the flag for marking 
tracks as a part of a gapless album: there is a COMM frame with the 
description iTunPGAP and the content of the frame must be
0x31 0x00 0x00

If the last 0x00 is omitted, iTunes won't recognize the file as part of 
a gapless album.

Kind regards,

Mp3tag - the universal Tag editor

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