Re: I dream of converting this file to a real mp3

On 10/28/08, Wesley J. Landaker <[email protected]> wrote:
> On Tuesday 28 October 2008 18:33:12 Kelly Jones wrote:
>> Is the sync word always 4 'ff' (decimal 255) in a row?
>
> I'm sorry, I led you astray; the sync word is actually three *nibbles* of f,
> not 4 bytes of ff. (I was apparently thinking of the sync word for a
> different format--I know about WAY too many file formats...) The fourth
> nibble in the 16-bit sync word is info about the version, layer, and error
> correction. So you are actually looking for ff fa (MPEG-1 Layer 3 ECC) or
> ff fb (MPEG-1 Layer 3 no ECC).
>
>> % \od -x jeannie1.wav | fgrep ffff
>
> Careful: od is showing these as shorts, but is byte swapping them for
> display. So faff and fbff are what we actually want in this display format.
> Note that because word alignment is not required (AFAIR) this could show up
> as ffxx xxfa or ffxx xxfb as well. Try "od -t x1" for an actual view of the
> bytes in order.
>
>> 0000440 9d09 364d ffff e8ff 6a32 3067 ed65 bf4d
>> 0000460 ffff faff ca0c 0634 d830 3064 3f03 f8ff
>                ^^^^
> So this looks like a MP3 frame header sync word. Despite the display order
> from od, the actual byte there stream is ff fa. There will be a sync word
> for every frame in the file, but of course you only really care about
> aligning with the first one.

Wesley, you're a genius! The following Perl one-liner does the trick:

# perl -0777 -pnle 's/^.*?\xFF(\xFA|\xFB)/\xFF$1/s' jeannie1.wav > jeannie1.mp3

I tried on several similar files and it worked great there too!

Generalizing it is a bit weird (double escapes required):

\ls *.wav | perl -nle 'print "perl -0777 -pnle \47s/^.*?\\xFF(\\xFA|\\xFB)/\\xF\
F$1/s\47 $_>MP3/$_.mp3"' | sh

I now have an MP3 library of TV theme songs. Muhahahaha!

-- 
We're just a Bunch Of Regular Guys, a collective group that's trying
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