[stella] One Bit Sound?

Subject: [stella] One Bit Sound?
From: Schwerin <schwerin@xxxxxxxx>
Date: Wed, 10 Feb 1999 00:26:09 -0500
Is there anyway to create hi-lo 1 bit squarewave audio ouput
with CPU control over the duration of the hi and lo states?

for example, to generate a squarewave:

        __________
______A|         B|___________C|...

where A, B, and C are non-equal time intervals.

If this were possible, then you could have a very crude digitized audio
playback engine.  Memory size, cpu usage, and cpu speed are the obvious
limitations to this method, but these three factors alone don't rule out
the possibility.

My idea is that any 8 bit or 16 bit waveform that we commonly use on our
computers can be reduced to zero crossings.  The original waveform is
translated into an interval format, consisting of a list of delay values
before forcing a zero-cross.  This is also good for generating multi tone
music.

I guess I'm hoping that I can use the volume registers as a zero cross
control, and set the tone registers to something helpful...

For example, to get access to a hi and lo signal, could I set the
oscilators to run opposite each other, set it to a low frequency, have
software "know" which osc is hi, and hope that the sine applitude going to
zero doesn't kill the effect?  I guess the problem is I don't want the
oscillators to oscillate!

If this is possible, the volume registers can be fully used to give more
resolution to the output waveform.

The other option would be to "model by clay" a custom audio ouput through
various register stores to the audio registers (a linear piecewise
synthesis).  This, however, is mind bogglingly complex, and doesn't
guarantee any specific level of fidelity to the original waveform.

-Andrew Schwerin
schwerin@xxxxxxxx



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