Just to confuse you, my response to multiple authors...
From: Glenn Saunders <krishna@xxxxxxxxxxxxxxx>
>I doubt that what you want could be done without extra hardware given the
>6507's clock speed and its everpresent task of updating the kernel.
I was thinking foremost of a sound demo without any graphics. But after
looking at Eckhard Stolberg's say.a65 it seems possible to run the sound
and the kernal, although the tradeoff is a lower sample rate.
He says the frequency is
262 lines * 60 frames / one sample every fourth line = 3930
which is what - 10 to 20 cycles every 4th line?
Sure, you want a better sample rate, there will be less drawing time
available. You also lose more time if you want to do more that a straight
one shot or repeating small table sample. My favorite idea is the
ocassional sound between levels, or at death, where you can give more CPU
time to the sound engine and it doesn't kill the game play too much.
...
From: Eckhard Stolberg <Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx>
>If you set the AUDCx register to 0 or 11, the output will
>always be high. You can generate complex waves by quickly
>changing the AUDVx register for that voice. I have posted
>some example code for this shortly after the list has started.
>You can find it in the archive or on Garon's site.
Nice. This was exactly what I wanted to hear. I found your postings on
this and I'm studying them.
So with two AUDV regs, it would be possible to A) mix two channels of
sample playback OR B) add some resolution beyond 4 bits to your sound
sample by clever manipulation of AUDV0 and AUDV1??
...
From: Lord Spambraticus of Borg <lord-of-hell@xxxxxxxxxxxxxxxx>
>Heheh, this is called Pulse Width Modulation (PWM), and yes, it can be used to
>very crudely playback digital samples.
Thanks, I thought it had a name. This is much better than my proposed
Audio Time Swap Thingie...I suffer from "Reinventing the Cylindrical Motion
Inducer" Syndrome.
>(The tool would convolve the time domain sample data into frequency domain.)
>This topic is intriguing enough to me to be tempted to muck around with Stella
So it seems simpler than we imagined. Use one oscillator and set it to
ride high as Eckhard explains, and reset the volume reg to generate the
waveform.
But don't try it on an emulator.
...
From: Chris Wilkson <ecwilkso@xxxxxxx>
>yes, you can set the tone to a DC voltage...voila! 8-bit audio via the volume
>regs. This is what I was alluding to before....
You mean 4bit right? Unless we do some clever V0 and V1 mixing.
>Look for say.bin on the Stella Archive.
I found it! Thanks.
-Andrew Schwerin
schwerin@xxxxxxxx
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