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

[Josh Green]

Hello FLAC list.

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 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).  The conversion to 24 bit would be a
problem in that case.

Best regards,
	Josh Green


On Thu, 2007-03-29 at 12:07 -0700, Brian Willoughby wrote:
> Hi Henry,
> 
> 32-bit float has exactly the same precision as 24-bit int.  I'm not  
> sure what the reference encoder does, but it would be possible to  
> write an encoder based on the FLAC library which converts 32-bit  
> float to 24-bit int when creating a FLAC-compressed file.  You could  
> also do the 32-bit float-to-24-bit int conversion with another tool  
> before using the standard flac encoder.  There would be no loss of  
> data so long as the original audio does not exceed +-1.0 in floating  
> point, in which case you'd need some way to handle clipping.  32-bit  
> float really only has an advantage for intermediate stages of audio  
> processing where it might not be a good thing to require clipping or  
> peak limiting until a later stage.
> 
> 32-bit int has more precision than 32-float, albeit less dynamic  
> range.  However, there are no 32-bit A/D converters out there, and we  
> really only need about 18.5 bits in any listening environment, so 32- 
> bit integer is not very useful.  It shouldn't be difficult to write  
> an encoder/decoder which supports 32-bit integer.  There is at least  
> one independent FLAC implementation, but I have no idea whether it is  
> open-source or supports 32-bit.
> 
> As it stands, FLAC is perfectly suited for compression and archival  
> of all original recordings and all final masters of audio material.   
> Only engineers and experimental researchers would need 32-bit for  
> their intermediate storage, and I believe it is typical to not  
> compress intermediate storage anyway.  In other words, there's no  
> real point for this support in FLAC, which is why it isn't there.
> 
> Do you have a specific need?  ... other than to see the support  
> listed as a bullet item on the feature list?
> 
> Brian Willoughby
> Sound Consulting
> 
> 
> On Mar 29, 2007, at 10:24, Harry Sack wrote:
> 
> Hi,
> 
> I have read this on a forum:
> 
> 'FLAC supports 24-bit audio fine. My understanding is that the FLAC  
> format also handles 32-bit ints, but the reference encoder does not  
> implement it, and FLAC has no support for float data. WavPack handles  
> all integer bitdepths up to 32-bit and also 32-bit floats.
> 
> Both codecs handle all sampling rates.'
> 
> I was wondering if there are plans to support 32-bit ints and float  
> data in the future, like WavPack does.
> 
> thanks in advance
>