flac dev - Jun 2014 - [PATCH] stream_encoder : Improve selection of residual accumulator width

Miroslav Lichvar wrote:
> I think it would be interesting to know how common are such streams. I
> patched flac to print a warning on decoding or testing when this is
> detected, but didn't find any files with this problem in my (small)
> music collection.
>
> If someone has a large collection and some cycles to spare, can you please
> consider compiling flac from git with the attached patch and see if
> you have any files that fail with "flac -t" ?
>
> With the known problem file (snippet6.wav) encoded by 1.3.0 it prints
> this:
>
> WARNING: residual -11025151 wider than bps 24
> WARNING: residual 41873263 wider than bps 24
> WARNING: residual -67175215 wider than bps 24
> WARNING: residual 69950995 wider than bps 24
> WARNING: residual -67108864 wider than bps 24
> ...
> WARNING: residual 11227392 wider than bps 24
> WARNING: residual -8754288 wider than bps 24
> snippet6.flac: ERROR, MD5 signature mismatch
It seems quite common for 16-bit files:

WARNING: residual 43536 wider than bps 16
WARNING: residual 38012 wider than bps 16
WARNING: residual 35263 wider than bps 16
WARNING: residual 40668 wider than bps 16
WARNING: residual -34199 wider than bps 16
WARNING: residual -33828 wider than bps 16
WARNING: residual -33891 wider than bps 16
WARNING: residual -33540 wider than bps 16
WARNING: residual -36793 wider than bps 16
WARNING: residual -38870 wider than bps 16
WARNING: residual -35610 wider than bps 16
WARNING: residual -39849 wider than bps 16
WARNING: residual -38411 wider than bps 16
WARNING: residual -33430 wider than bps 16
WARNING: residual -34989 wider than bps 16

I don't have 24-bit FLAC files in my music library.

op 19-06-14 20:17, lvqcl schreef:
> It seems quite common for 16-bit files:
I second that. Apparently it depends on the kind of music, some 
albums have no warnings (mostly classical music it seems), some 
have over 20 per file. I've seen a few with > 100 per file 
(things like rock and heavy metal). Most of the FLAC files were 
encoded with FLAC 1.2.1.

The same is true for 24-bit files. I checked some orchestral 
music with no warnings, while NIN's The Slip (downloadable free 
of charge in 96/24) does, track 2 gives ~ 1900 warnings. These 
files too, were encoded with FLAC 1.2.1

On Thu, Jun 19, 2014 at 09:23:26PM +0200, Martijn van Beurden
wrote:
> op 19-06-14 20:17, lvqcl schreef:
> > It seems quite common for 16-bit files:
> 
> I second that. Apparently it depends on the kind of music, some 
> albums have no warnings (mostly classical music it seems), some 
> have over 20 per file. I've seen a few with > 100 per file 
> (things like rock and heavy metal). Most of the FLAC files were 
> encoded with FLAC 1.2.1.
Thanks for the data.

I think I was just confused. The residual seems to be always handled
as 32-bit and it's only added to the original signal, there is no
multiplication, so it shouldn't be a problem.

-- 
Miroslav Lichvar