[flac-dev] exhaustive-model-search issue results in multi-gigabyte FLAC file
Martijn van Beurden
mvanb1 at gmail.com
Wed Jul 17 02:20:00 PDT 2013
On 16-07-13 12:32, Leigh Dyer wrote:
> The first time I tried, the resulting file encoded just fine, but after
> trying a few more times, cutting at slightly different points, I was
> able to get a snippet of that section that exhibits the problem. This is
> short enough that I think I can link to it here:
>
> http://wootangent.net/~lsd/blah/snippet6.wav
>
> This results in a 4.1GB file when encoded with -7.
Have you notices that there are a few damaged areas in this file? For
example at 4.854 seconds, 6.700s, 6.828s, 7.618s. It looks to me like
damage accumulated during some process after mastering, somewhere in the
process of transferring it as a WAVE-file. You might want to check this
with the band that uploaded it to you.
In any case, it looks like these damaged areas triggered some unwanted
FLAC behaviour. You've exposed at least two very serious FLAC bugs,
namely a malfunctioning RICE2-partition encoder and a bug concerning
choosing verbatim frames over fixed/lpc frames.
One last remark for anyone who didn't notice yet, this >4GB flac file
consists mostly of zeros, zipping it reduces the file to 6.8MB. Looking
at it with a hex-editor reveals this has to be an error with the RICE2
partition. When this snippet is encoded with FLAC 1.3.0 with everything
left default except setting the compression level to 7, the problem is
in frame 52 and frame 73
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