[Flac-dev] flac improvement??

Josh Coalson xflac at yahoo.com
Sat Oct 14 19:48:25 PDT 2006

--- Ludovico Ausiello <lausiello at arces.unibo.it> wrote:
> hello my name is Ludovico Ausiello, i'm a ph.d at the university of
> Bologna 
> and I've developped an open source alternative to proprietary philips
> superAudioCD encoder (that actually cost some thousands dollars!)
> that has 
> better performance (it's seems strange.. but..) I'm interested to use
> the 
> flac encoder to compress the 1-bit stream that is the output of my
> encoder 
> (I start from 24 or 32 bit wav and then i encode them into a 1-bit
> stream, 
> like in the superaudioCD format). my problem is the sample rate.
> eventually the normal commercial format proposed by philips and sony
> was
> signal band = 22.050 HZ => Fs = 44.100 Hz
> Over Sampling Ratio = 64 => Total bit rate = 64*44.100 = 2.822.400 Hz
> so the superaudio CD uses a 1-bit stream at that sample frequency
> I've developped a new algorythm that beat philips'one of at least 3.7
> dB in 
> Signal to Noise Ratio (the best is a +9.2dB!) and also reduce the
> power 
> consumption of the digital amplifier required to drive the speaker of
> a 
> factor of 5 (you can ask and i'll send you a pdf copy of my paper i 
> presented at the Audio Engineering Society convention of the last
> May..)
> I'm very interested in extending the FLAC limitation of sample rate
> (i've 
> read it is 1 MHz!) and i wish to ask you if it's possible to encode
> also 
> these 1-bit streams and then make them playable by an ipod
> hoping to receive some help i can only say that the work that you
> already 
> done is amazing, and (if you are interested in testing my algorythm)
> i'll be 
> pleased of sending you my source code files.

thanks Ludovico.  there are two minor limitations, one that you
discovered is the max sample rate, and the second is the minimum
sample size of 4 bits per sample.  but these are actually only
limits because of how they are represented in frames, but...

the fundamental problem is that all of FLAC's algorithms are
designed for linear PCM samples and probably wouldn't compress
SACD/similar streams very well.


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