[ID3 Dev] Sync-safe sizes?

Ben Bennett fiji at ayup.limey.net
Thu May 17 05:58:36 PDT 2007

On Thu, May 17, 2007 at 04:41:55PM +1200, Mike van Bokhoven wrote:
> I was wondering about that - I was beginning to think about really awful
> ways to verify the frame size, such as checking for an apparently valid
> frame header following each frame before the last one. Wrong for several
> reasons, but when reading a 2.4 frame with obviously invalid sizes, what
> else can be done?

Unfortunately that is all we can recommend.
> For now, my app will continue to write 2.3 by default I think, it seems
> safer. Once I get to grips with ID3 better (have been working with it for
> the grand total of a day or so) I might look at going to 2.4, if the support
> is out there. 2.3's been quite co-operative in general; I'm reading, parsing
> and updating the basic standard frames, and writing all frames out again.
> Working on APIC support now, hence the size problem!

2.3 support is far more consistent and writing 2.3 frames is the best
you can do if you want wide interoperability.  Unfortunately taglib
gets the meaning of some 2.3 stuff wrong and only writes (valid) 2.4.
But 2.3 is still a better choice 'cause it at least can be read.

As noted by others, there are a couple of threads about this in the
archives.  Someone from Apple was paying attention for a while and
there were noises about getting the 2.4 frame sizes fixed... but I am
not holding my breath.


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