[ID3 Dev] Windows Media Frames appear to use invalid FrameSizes

[Pyt]

Is it a v2.3 or v2.4 tag ? v2.3 does not have the notion of synchsafe 
integers for frame sizes. The size as coded would be correct in a v2.3 tag.
 Pyt.

 On 6/9/05, Brian Mearns <bmearns at coe.neu.edu> wrote: 
> 
> 
> I'm trying to parse some id3v2 tags off an mp3, and I keep running into
> problems with a PRIV frame, with no Owner identifier and private data
> beginning with: "WM/UniqueFileIdentifier", and then a bunch more after it. 
> I
> can tell visually that the frame is 148 bytes, giving it a FrameSize of 
> 138.
> For some reason, whoever wrote the tag stored the whole value in the first
> byte of the size, making it 10001010 ( -118 in signed dec), and thereby
> breaking with the synchsafe standard. Based on the "WM" preceeding the
> data--and there are several other "WM/..." PRIV frames in the file--I'm
> thinking it's something Windows Media player is doing, but I'm not 
> positive.
> 
> 
> Has anyone else come across such a thing before, or have a good ideaof how
> to handle it? I can put some hooks in my code to handle it, but I'd rather
> not write it out in this broken format, so if I ever get a tag which 
> doesn't
> syncsafe any bytes in the size, I'm going to be in trouble.
> 
> Just in case I'm missing something stupid, here are the bytes in the frame
> (in hex, obviously). Note the 8a in the 8th byte (1-based), the last byte 
> of
> the frame size element.
> 
> 50 52 49 56 00 00 00 8a 00 00 57 4d 2f 55 6e 69 71 75 65 46 69 6c 65 49 64
> 65 6e 74 69 66 69 65 72 00 41 00 4d 00 47 00 61 00 5f 00 69 00 64 00 3d 00
> 52 00 20 00 20 00 20 00 33 00 36 00 37 00 39 00 39 00 32 00 3b 00 41 00 4d
> 00 47 00 70 00 5f 00 69 00 64 00 3d 00 50 00 20 00 20 00 20 00 20 00 33 00
> 38 00 33 00 38 00 33 00 3b 00 41 00 4d 00 47 00 74 00 5f 00 69 00 64 00 3d
> 00 54 00 20 00 20 00 35 00 31 00 33 00 39 00 34 00 39 00 39 00 00
> 
> 
> 
> -Brian Mearns
> (bmearns at coe.neu.edu)
> 
> 
> 
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