[Flac-dev] Idea to possibly improve flac?

Brian Willoughby brianw at sounds.wa.com
Fri Jan 7 21:31:47 PST 2011

On Jan 7, 2011, at 18:08, Declan Kelly wrote:
> On Fri, Jan 07, 2011 at 05:11:26PM -0800, brianw at sounds.wa.com wrote:
> [NIN 24/96]
>> Thanks!  That's interesting to note.  I think that I ended up with
>> the true 24/96 files, but I am curious: How do you tell whether you
>> have the full 24/96 or not?
> Extract to WAV, do a hex dump, and look for repeated 0x00 bytes.  
> Someone
> on the hydrogenaudio forums did that, reported it on the NIN  
> forums, and
> Reznor got the reissued 24/96 FLAC'd and seeded on tracker.nin.com  
> in a
> couple of days.
My 16-bit detector does exactly that, except that it only looks for  
0x00 in the lowest 8 bits of each sample.  I used to use hexdump, but  
didn't trust my eyes when scanning manually.  With a program, there  
aren't any false positives for 0x00 bytes in other positions.  What  
it does is scan until the first sample is found with something in the  
lowest 8 bits, and then reports the file as true 24-bit and quits  
early.  If it scans the entire file without finding any 24-bit  
values, it gives the sad news that it's really 16-bit samples  
disguised as 24.

By the way, I had to special-case 0x00800001 and treat it as 16-bit.   
I don't know whether it was the MOTU 896HD or Logic, but something  
was creating that one value in the midst of an otherwise 16-bit pure  
file.  But there are tens of millions of other 24-bit values, so  
ignoring that one won't create a false report.

>> 16-bit audio samples stored in a 24-bit file format.  Frequency
>> analysis makes it obvious whether the content extends above 20 kHz.
> Google for that hydrogenaudio thread: Reznor made one post on it, and
> mentioned that the recording was done at both 24/96 (Lavry) and 24/192
> (Apogee) on all songs, and they chose whichever they preferred at mix
> time.



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