[Flac-dev] Re: FLAC: same features as WavPack

[Harry Sack]

2007/3/29, Brian Willoughby <brianw at sounds.wa.com>:
>
>
> 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 fixed?
>
> 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?
>


yes sorry, I was just curious about the status, I have never tried 24-bit
myself.

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 point
> > 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 audio technology.
>
> 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 circles.
>
> 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 exponent.
>
>
> 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.
>


thanks, now it's all clear for me !

Brian Willoughby
> Sound Consulting
>
>
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