[Flac] FLAC suddenly compresses more - why?

[rappard at dds.nl]

> On Dec 27, 2010, at 07:10, Fernando Alberto Marengo Rodriguez wrote:
>> If you want to be sure that you get no information loss, I suggest
>> a very simple test. Recover your WAV file from any of the FLAC
>> files you mentioned in your e-mail. If this WAV file is bit-by-bit
>> identical to the input WAV file, then you have no information loss.
>
> This is a good test, but keep in mind that only the audio part of the
> WAV file will be identical.  There are non-audio parts to a WAV file,
> and those may be lost or changed when compressed, so you will need
> some method of comparing only the audio and not the rest of the
> file.  In other words, a basic file to file compare might fail even
> if the audio is the same.
>
> I'm not sure how to compare the audio part only, at least not
> easily.  You can place each file in the same DAW, but with one set
> for inverted polarity.  Then mix them together and you should get
> silence.  But that is not an easy or simple test.

Caveat: I've never tried any of these, but these have come up in
various HA threads I've read over the years:

Audacity
EAC: Compare WAVs (CTRL-W)
foobar2000: bit-compare two tracks
(http://www.foobar2000.org/components/view/foo_bitcompare)

Cheers,

Martin