[Flac] FLAC suddenly compresses more - why?

[Gregory Maxwell]

On Mon, Dec 27, 2010 at 6:21 PM, Brian Willoughby <brianw at sounds.wa.com> wrote:
> 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.

Use raw files. E.g. the --force-raw-format with the flac command line command.