Date   : Wed, 19 May 2004 15:24:32 +0100
From   : Richard_Talbot-Watkins@...
Subject: Re: Sound wave representation

Charles Ripperton wrote:

> --- Richard Gellman <splodge@...> wrote:
>
> > For extra resolution you can use some devious channel-combining.
> > Since the amplitudes of each channel are combined to give a final
> > output, you can use the relative amplitudes of the channels to
> > increase the resolution. Superior Software used this technique for
> > its audio samples.
>
> Where are the relativities of the channels' amplitudes defined?

The volume scale is the same for every channel, but obviously using 3
channels rather than 1 effectively gives a three-fold increase in
volume resolution.

Not sure how the sound channel amplitudes map to actual perceived sound
volume - as far as I know though, it's not a linear scale.  At least
when I was emulating the sound chip for my Sega Master System emulator
on the Archimedes (which uses the same sound chip as the Beeb), I found
I had to use a non-linear (vaguely exponential) scale in order that it
sounded right.  It'd be interesting to sample the output of a Beeb at
all 15 volume levels and see what each volume corresponds to.  Has
anyone already done this anywhere?

Rich



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 SCEE 2004