Looping DAC and other issues

[Simon Williams <DON'Temail@luddite.ca>]

On 08 Dec 2002 09:07:32 GMT mjmahon@aol.com (Michael J. Mahon) wrote:

> 
> Simon Williams wrote:
> 
> >Is anyone else working on anything Apple II and musical? I'd heard a
> >rumor some time back that a new version of DAC.522 was coming that 
> >supported seamless looping... anyone hear anything about that? ;-)
> 
> Ok, Ok--I heard that.  ;-)
> 
> I've had it working for some time now...
 
> There is one issue, though, and that is that it currently exists only
> in the version that is embedded in the part of the hi-res screen that
> is hidden by the text lines in "mixed" mode.  I'll take another look
> at whether there are enough spare cycles to make it work in the
> contiguous memory version.

Maybe the developers kit will include a self-compiling version that will
hide itself in any HiRes graphic... :)

There are a few things I've been trying to figure out about DAC.522,
which I imagine probably relate also to other DACs:

1) Is the sampling rate 22K or 11K? I notice that resampling from 11025 
   Hz has no effect on the sample.

2) Is the carrier frequency of digitized sound the same as the sample
   rate or half of it? I seem to recall reading that the highest pitch
   reproduced is always half of the sample rate.

3) How does DAC software 'read' sound? Is there any correlation between
   the bytes of a sound file and its waveform? I've been examining sound
   files with an eye to creating new sounds either graphically or num-
   erically, but so far nothing's clicked...

Um... I think that's it... for now at least.

-SW