[linux-audio-dev] synthesis on gp2x .. (was Fwd: RE: [gpx-dev] hardware interfaces)

[Alfons Adriaensen]

On Thu, Jan 12, 2006 at 10:52:58AM -0500, Paul Davis wrote:

> i can just about begin to imagine how one might write a JACK and a
> JACK client that could run on fixed or floating point, but beginning is
> where i give up.

JACK itself shouldn't be affected too much. Apart from the dithering
it does not do any processing. 

The standard sample type could be a signed 32 bit, with bits 23 downto
24-N mapped to N-bit hardware. On input bits 24..31 are sign extended
from bit 23, on output the values are clipped as they are now. In other
words, the standard format could be 9.23 fixed point. This makes the
hardware resolution transparent to clients and accomodates all hardware
up to 24 bits (it's useless to go beyond that).

If you look at the history of digital audio, most of it was integer
or fixed point. There is a enormous amount of knowledge gathered over
the years on how to do things correctly in that format. I can still
remember the JAES papers on how to avoid limit cycles in IIR filters
etc...


-- 
FA