[ID3 Dev] APIC frame unsynchronization

Michal Vician id3v2 at audiott.com
Thu Nov 24 14:29:43 PST 2005


I'm lucky you assured me that I was right.
I'm just wondering that there are so many applications which do not work
according to Id3v2 specification. That's terrible...

Thanks
Miso

> Unsynch must be used only if you decide to.
>
> In v2.3, there is a global unsynch bit that says whether the tag is
> unsync'd
> or not. If this bit is set, all frames have to be unsync'd.
>
> In v2.4, there is a bit per frame to specify whether a given frame is
> unsync'd. If the bit is not set, you shall leave the FF's alone... :-)
>
> Hope this helps,
> Pyt.
>
>
> On 11/23/05, Michal Vician <id3v2 at audiott.com> wrote:
>>
>> Hi guys.
>>
>> I have a problem and need advice:
>> I've just written library which handles APIC frames. The writing process
>> looks like this:
>>
>> 1. create an array of bytes which represents entire APIC frames
>> 2. write the byte array to ID3v2 tag
>> 3. if there is at least one FF Ex byte combination present use the
>> unsynchonization scheme
>>
>> Is this correct?
>>
>> Now, why am I asking you this?:
>> I've downloaded some applications which support APIC frame. As far as
>> this
>> applications are concerned they do not use unsynchronization scheme when
>> writing the APIC frame - they are not able to show pictures written with
>> my library.
>> I'm just wondering why don't they use it?
>> Is it just a bug on their side or am I wrong if I claim that
>> unsynchronization must be used whenever the false sync bytes are found
>> (FF
>> Ex).
>>
>> Regards
>> Miso
>>
>> --
>> Michal Vician
>> id3v2 at audiott.com
>> http://www.audiott.com/
>>
>>
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>>
>


-- 
Michal Vician
id3v2 at audiott.com
http://www.audiott.com/


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