Re: [Atari800-users] New pokey sound performance on ARM

[Piotr F. <pf...@op...>]

> Please wait for me to give to Kostas and probably you my fixed-point
> implementation. It could be a good starting point, because I
> designed it carefully. Care should be always taken when doing such
> things.
> 
Okay.

Two more questions:

1. mzpokeysnd seems to round the 1.77MHz rate to a multiple of the output
   sample rate. While this probably doesn't degrade the quality,
   it probably makes it impossible to emulate POKEY cycle-exactly
   at the speed identical to the real chip. Normally the 1% difference
   in speed is not noticeable, but imagine that you want to play
   a music for exactly 3 minutes and 20 seconds (I want to
   implement song lengths in ASAP). 1% difference in speed
   makes a difference of as much as two seconds.
   I guess it is possible to resample from the rate of 1773447 +- 100 Hz
   with just a longer table of coefficients, but no additional costly
   calculations ?

2. What is the mapping of (AUDC&0xf) to the output level?
   I mean, is it truly linear?
   atari++ seems to apply gamma mapping on the samples
   and the documentation of the NES sound chip gives an equation
   of the form: outvol = A / (B / sum(vol) + C).

Piotr