[Flac-dev] [BUG] --sector-align zero padding is not entirely zero

[Josh Coalson]

thanks, will take a look.

Josh

--- Dave Chapman <dave at dchapman.com> wrote:

> Hi,
> 
> A user at the www.thetradersden.org website reported a difference
> when
> fixing "sector boundary errors" in CD-quality WAV files with shntool
> and
> flac.  As as result of investigating this, I think I've found a bug
> in
> the zero-ising of the buffer used to zero-pad the last file when
> encoding with the --sector-align option.
> 
> My test consisted of the creation of four "non-aligned" CD quality
> WAV
> files.  I then "fixed" these files using both the "shntool fix"
> command
> and the "flac --sector-align" command.
> 
> I then compared the WAV files created by shntool and the WAV files
> created by uncompressing the FLAC files, and the MD5 checksums did
> not
> match for the final track.
> 
> On comparing the contents of the WAV files, the "shntool" fixed
> version
> correctly contained 448 zero bytes at the end (112 samples). 
> However,
> the FLAC version contained 224 zero bytes, followed by 224 non-zero
> bytes.
> 
> I've tracked the bug to the calculation of the number of bytes to
> fill
> the input_ buffer with, which is calculated in line 778 of encode.c
> as
> follows:
> 
> data_bytes = wide_samples * (bps >> 3);
> 
> However, my understanding is that the input_buffer is always an array
> of
> 32-bit integers, and therefore the calculation should always be:
> 
> data_bytes = wide_samples * 4;
> 
> The expression (bps >> 3) is also used elsewhere in encode.c so you
> may
> wish to examine those instances as well for similar bugs.
> 
> Best wishes, and thanks for FLAC.
> 
> Dave


		
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