PRIV ID3V2Tag and length

Avi Treistman avi at
Sun Sep 29 15:27:31 UTC 2013

Hi Scott,

Thanks for your answer. What I did not realize is that bit 7 of each byte is ignored in the tag size field, so as soon as the tag went over 127, it appeared to be doubled in size., so the length of 0xA21 is actually 1313, wchi is consistent with the payload length.



Hi Avi -

On Sep 16, 2013, at 1:07 PM, Avi Treistman <avi at> wrote:

> For example , on a payload of 1300 bytes, I am receiving a frame 
> length of  2593

I think there must be something else going on in your code that's causing the problem.  This snippet:

Produces the (expected) output of:

=== test.mp3 ===
PRIV Frame Size: 19

Are you perhaps referring to the total tag size and not the frame size?  TagLib's ID3v2 implementation pads the end of tags so that small changes don't require rewriting the whole file.  Almost all ID3v2 implementations do that.


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