[Flac-dev] Re: FLAC: same features as WavPack
brianw at sounds.wa.com
Thu Mar 29 13:15:12 PDT 2007
On Mar 29, 2007, at 12:44, Harry Sack wrote:
> 2007/3/29, Josh Green <josh at resonance.org>:
> As far as I know 24 bit FLAC support is broken. It often doesn't
> compress the audio at all, but instead stores the chunks as verbatim
> type (although the FLAC format supports 24 bit). Perhaps this is
> If so, do let me know.
> I also want to know if this is fixed.
Harry, your question doesn't make it clear as to whether you're
actually having a problem, or just curious about the answer. Josh
Green says he's having a problem where compression doesn't seem to
work. Harry, are you actually seeing a problem with 24-bit? What is
the problem you're seeing? Are you just writing in because you're
curious about the status?
There actually is no problem with 24-bit support, as I stated
earlier. So before people start chiming in with "me too" - I'd like
to request that you actually say what problem you're seeing, along
with a few details. Let's not start a rumor fest here.
> I agree that perhaps 32 bit float/pcm isn't
> entirely necessary when it comes to storing different qualities. But
> when wanting to preserve floating point audio, I would think it
> would be
> a nice feature. I believe 32 bit floats have a precision of 23 bits
> when the audio is +/- 1.0, so in theory that would mean that 24 bit
> would have more precision but less dynamic range (if the floating
> range is outside of +/- 1.0).
> Is it possible to explain me a bit further what "less dynamic
> range" exactly means? Can this difference actually be heard and if
> yes, in what audio quality sources? I have just discovered FLAC and
> I'm not an audio professional, but I wanted to know what the "real"
> difference between 32 bit float and 24 bit int precission is when
> comparing audio quality.
You cannot hear 32-bit audio because there is no such thing as a 32-
bit digital-to-analog converter. And there is absolutely no floating-
point D/A of any bit-depth. So you cannot compare the audio quality
of 32-bit to anything. All digital audio must be converted to 24-bit
or less before you can hear it. This conversion is not part of FLAC,
so you probably should look elsewhere to learn about general digital
FLAC is lossless when compressing any audio that comes from an A/D.
FLAC is lossless when compressing any audio that is properly prepared
for D/A, and thus ready for listening. Any other format not
supported by FLAC is an intermediate format used by audio engineers
and not typically for distribution, except perhaps in scientific
Note: there are non-linear DACs for 8-bit codes, but those are not
true floating point, even though the bit code has a mantissa and
> And I'm also guessing for reasons why WavPack actually uses 32 bit
> floats. Is it true then that FLAC is not completely lossless if you
> look at the encoder when using 24 bit int's vs. using 32 bit
> float's? Does this storage thing influences the audio quality of
> just regular Audio-CD quality (16 bits, 44.1 kHz, stereo) after
> compression, because that's the main reason I use FLAC.
Lossless means lossless. 16/44.1 CDDA audio quality is identical
before and after FLAC. CDDA audio does not use 24-bit or 32-bit
codes at any point. It is all 16-bit integers.
FLAC does not support 32-bit float, so it is pointless to say whether
it is completely lossless when storing 32-float as 24-bit int. If
you convert 32-float to 24-bit outside FLAC, then the loss occurs
elsewhere, not in FLAC. FLAC is completely lossless for all formats
that it supports. I'm sorry that I confused things in my earlier
message by pointing out that you can convert 32-bit float to a format
that FLAC supports or that you can write your own encoder/decoder for
32-bit integer FLAC. You really need to understand floating point
numbers and what kind of audio data you have before trying to analyze
FLAC this way.
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