[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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