From: John Joyce <dangerwillrobinsondanger@...>
Date: 2007-08-16T15:52:32+09:00
Subject: Re: mp3 file magic number identification


On Aug 16, 2007, at 1:30 AM, Ben Bleything wrote:

> On Thu, Aug 16, 2007, John Joyce wrote:
>> Though I'm going to need some testing... the magic file (not always
>> easy to read)
>> says this :
>> # MPEG 1.0 Layer 3
>> 0       beshort&0xfffe  =0xfffa         \bMP3
>>
>> I'm not 100% sure, but Adam said 0xFFFB or 0xFFFA, and the magic file
>> lists only FFFA or does it mean FFFE and/or FFFA ?
>
> Do "man magic" (or possibly man 5 magic, or man -s 5 magic), and it
> should describe the format of the file.  Basically, it's offset, type,
> magic, message.  Numeric types can be specified with &0xnnnn, where  
> the
> number is ANDed with the magic.  I'm basically just quoting from the
> manpage, though, so give it a gander.
>
> Unix is cool :)
>
> Ben
>
Yeah, I read that already. Seemed simple. Many file descriptions are  
readable, but the MP3 one is one of many that don't make sense to me.  
" Numeric types can be specified with &0xnnnn, where the
> number is ANDed with the magic."
Makes no sense to me at all. I'm not a C person really.


>> # MPEG 1.0 Layer 3
>> 0       beshort&0xfffe  =0xfffa         \bMP3
So what does the above mean??
I see hex numbers. but what is that '=' doing ?
That's cryptic.
The other lines after that make sense. They all describe the second  
byte and that it determines the bitrate.
so do I care about 0xfffe? or 0xfffa?
or both?
I'm hoping I'm doing this right.