Re: [stella] Berzerk Voice

Subject: Re: [stella] Berzerk Voice
From: "Eckhard Stolberg" <Eckhard_Stolberg@xxxxxx>
Date: Thu, 15 Aug 2002 15:59:45 +0200
> Unfortunately, very little in the way of details there. I want sample
> bit depths, etc, darnit! :)  Any chance of getting the author to post here
> explaining how he did it?

Since Mike said he was inspired by the sampled voice demo that I posted
to the Stella list in early 1997, I guess it's OK, if try to answer this
question. ;-)

It's 4 bit at about 4000 Hz. Basically you set the audio control register
to constantly outputing a high signal, and then quickly change the 4 bit
volume register. In this example the volume gets changed every 4 scanlines,
which results in a sample frequency of about 4000 Hz. For the robotized
voices in Berzerk this seems to work quite well. Since changing the sound
data so often doesn't leave you too much processing time to generate the
game display, Mike blanks out the screen while he plays the sampled voices.

Where Mike got the samples from I don't know. But I suppose he just
downsampled the audio files for the MAME Berzerk emulation or something.

> I'd really like to know what this would sound like, or if it's already
> done. The hardest part of testing this technique would be generating the
> data. Parsing a WAV is easy, but determing the average frequency of each
> chunk would require a Fourier transform or similarly hairy algorithm.

That's an interesting idea, but at 60 changes per second, I fear it
would sound more like the "talking" of the guy in Little Computer people
than any recognizable words.

Ciao, Eckhard Stolberg

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