Re: Software-based mixer for Ensoniq?

[dempson@atlantis.actrix.gen.nz (David Empson)]

In article <21SEP199500073699@vax2.concordia.ca>,
Mitchell Spector <spector@vax2.concordia.ca> wrote:
> 	I'm curious, is it technical possible to write a software-based
> sound mixer for the IIgs? Something that would be loaded into memory and
> remain accessible from within all applications (ie, an INIT, CDA or NDA).
> One of the major functions of such a program would be increasing or 
> decreasing the volume level of Ensoniq chip.

Not likely.  With the exception of playing back simple digitized
sound, most IIgs sound programs operate by continually updating the
Ensoniq volume registers to implement envelopes.  The sound RAM
contains the raw sample of the instrument being played.

> Also nice would be controls for adjusting bass, treble

This would require some kind of frequency-based amplification, which
would be next to impossible to do in software (it would require
modification of the sampled waveform).

> and stereo channel balance.

Again, not possible in general.  Specific programs might be able to
simulate balanced stereo by setting up two generators to play the same
waveform at different amplitudes.  If envelope-style updating is
required, they would have to use scaled values for the volume
registers for each channel.

> I've seen this done on a PC system with certain audio cards, you can
> call up a little mouse controlled graphical mixer or once in a game
> or application, use key presses (ie, control-Alt-U/D) to adjust
> volume output.  

They probably have special hardware support for bass/treble
amplification and stereo balancing.  It could be done on a IIgs with a
special sound card that did post-processing of the signal from the
Ensoniq before the amplification and output stages.

> 	I recently added a pair of Bose Roomate speakers to my stereo
> card with _no_ volume control.

Which stereo card?  Some (e.g. the SoundMeister) have their own
software-driven volume control.

> Some games and applications allow you to adjust volume through
> software, but many will not, keeping the volume at a fixed constant.
> Adjusting the "Sound" option from the Control Panel obviously doesn't
> affect anything but the internal speaker

And the external speaker connector.  It doesn't affect stereo cards.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand