24-bit data type (was:RE: 24-bit wav files and other observations )

[Schirmacher, Rolf]

> -----Original Message-----
> From: Daniel J Sebald [mailto:daniel.sebald at ieee.org]
> Sent: Friday, February 22, 2008 2:01 AM
> To: John W. Eaton
> Cc: octave maintainers mailing list; Paul Kienzle
> Subject: Re: 24-bit wav files and other observations
> 
> 
> John W. Eaton wrote:
> > On 21-Feb-2008, Daniel J Sebald wrote:
> > 
> > | I wanted to read a WAV file with 24 bit data width using
> > | auload()--rather than the 8, 16, or 32-bit facility.  

...

> > 
> > | 2) Why does Octave/Matlab not have 'uint24' throughout?  For
> > | example, there'd be nothing unusual about
> > | 
> > |   data = fread(file, samples, 'int24', 0, arch);
> > | 
> > | and a type 'int24'.
> > 
> > What general-purpose systems have 24-bit ints as a native data type?
> 
> Well, probably few general-purpose systems.  There are many 
> 24-bit embedded processors, of course, and then there are 
> plenty of data files that use 24-bit data.  So, from an 
> analytical standpoint there are reasons for having 24-bit 
> "native" types.  It's similar to the situation that we have 
> very few 8 bit CPU's anymore, but the 8-bit width "native" 
> format is still ubiquitous.
> 

I would like to advocat the idea of int24. The main reason is not because it
is a native format for general-purpose systems. But is is actually going to
be one of the most relevant audio formats with 24 bit A/D and D/A converters
replacing the 16 bit converters for the higher qualities (and thus the 24
bit .wav format get more popular...) and whole DSP series are using 24 bit
as native format (e.g. Motorola/Freescale DSP 56xxx) to allow high dynamic
range calculations for 16 bit I/O-data without scaling concers (e.g. at
filtering). As one of the most interesting applicatoins of the fixed int and
uint data types is modelling the behaviour of integer processors (i.e. of
calculations performed on them), having an int24 would be quite interesting,
e.g. for modelling filter calculations of audio data / DSP operations.

Rolf