> Looping maybe?
>
I'll have to look. Thought I had it memorized, but obviously not... ;-)
> Sounds nice, most everything in one package! ADPCM also works well
> with music
> and sound effects (as opposed to some of the talking chips specialized
> for voice
> that use LPC, GSM, etc).
>
Yep. You can actually clock the thing at whatever rate you want...
16-20KHz might be a good compromise for duration of samples vs. ROM
space. I doubt the speakers in most games are good for much beyond
that. I guess we can run spectrum analysis on the samples to make sure
we're not going to trash any high-frequency stuff.
> They only thing that I would see as a pain would be for sounds that
> ramp up/down
> in frequency. Can the different channels have there sample rates
> individually
> controlled? Maybe that's one of the control words? Something like
> this will be
> needed to emulated some of the frequency changes needed in things like
> the
> background throb of Star Castle.
>
Sample rates are fixed except for a global external "rate" select.
Basically something like high-gear and low-gear. Sample clocks are
derived from either a 384Khz oscillator or a 4MHz crystal (I believe).
> Many sounds are just square waves that could possibly be controlled
> directly be
> the processor. But it would be nicer to have them play through the
> OKI chip for
> volume control. Once again if music will need to be played (4096
> tones for
> Boxing Bugs) we'll need to be able to control the playback sample
> rate.
>
Hmmm. Good point. Maybe we should start with a list of all the games
that will be supported in the Multigame, and work from there. (If BB is
the only game using that square-wave music and it's not in the Multigame
is might make sense to blow it off for now?)
[Zonn's next message...]
I'm wondering what the drive frequency of the OKI parts are
(Clay?). Is it in
the khz or mhz range? Could we drive the part from one of the
timer out pins of
the micro and control it's samplerate that way?
You don't have to use OKI's clock rates (other than you probably can't
exceed the top-end by too much). I noticed that Atari used non-standard
rates on Nightmare, and these telephone voice-mail boards I have seem to
be using 3.579MHz colorburst crystals instead of 4MHz...
I bet we could use software PWM from a PIC with rates around 384KHz
without too much trouble.
Two or three OKI chips with at least one of them's clock under
micro control
might work.
We need to determine the maximum number of simultaneous sounds actually
occur during gameplay. For the Sega stuff, I'm tempted to just use the
OKI solution for Space Fury, Eliminator, Zektor, and the speech boards.
StarTrek and Tac/Scan both use the USB, so I don't really see the need
to replace that unless there's a lot of people w/out Universal Sound
Boards that have the Sega Multigame...
-Clay
Received on Thu Apr 23 15:18:47 1998
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