From: rogeraw@dhhalden.no (ROGER ALLAN WAHLGREN)
Subject: Re: COMMODORE - HERE'S A CLUE
Organization: Ostfold College
Date: Tue, 13 Oct 1992 12:21:08 GMT

In article <35689@cbmvax.commodore.com> grr@cbmvax.commodore.com (George Robbins) writes:
>From: grr@cbmvax.commodore.com (George Robbins)
>Subject: Re: COMMODORE - HERE'S A CLUE
>Date: 8 Oct 92 22:54:45 GMT
>In article <1992Oct8.152203.27725@murdoch.acc.Virginia.EDU> ccb8m@onyx.cs.Virginia.EDU (Charles C. Bundy) writes:
>> grr@cbmvax.commodore.com (George Robbins) writes:
>> 
>> >In article <1992Oct5.180757.1@cc.helsinki.fi> jalkio@cc.helsinki.fi writes:
>> >> In article <OA92-901-306p1_88E8203B@piraya.bad.se>, 
>> >> Hans_Bergengren@p1.thulos.bbs.bad.se (Hans Bergengren) writes:
>> >> > 
>> >> >  GR> Not even Atari was dumb enough to try and create a custom chip that
>> >> >  GR> did 16-bit audio, the job is much better given to a DSP to handle.
>> >> > 
>> >> > It's NOT! Suppose you want the DSP to do other stuff, like voice 
>> >> > recognition, image enhancing, or 3D graphics, or any other of that 
>> >> > nice stuff a DSP can do, why waste bandwidth on such a simple task 
>> >> > as outputting audio?
>> >> 
>> >> Hey! As far as I have understood, the DSP is NOT needed for Audio output
>> >> (even 16-bit stereo, or maybe 8-channels). There is a special
>> >> audio-matrix-subsystem for that. You use the DSP, if you want some
>> >> realtime audio processing.
>> >
>> >From the description of the "audio matrix" it sounds like some analog 
>> >multiplexing of the audio signals.  This suggests that you can combine 
>> >the DSP and the other on-board noisemakers in various clever ways, but 
>> >the DSP is probably the only on that can generate 16-bit audio.
>> >
>> >It could be something better, but don't assume that something nice sounding
>> >like and audio-maxtrix-subsystem offers more than offered by the basic 
>> >on-board resources.
>> >
>> 
>> I have one simple question to this ongoing thread :)  How on earth can a
>> DSP "generate" any kind of audio?  Does it have an ADC?  Your bit limit
>> range on sound comes from the ADC not the 56K DSP in the falcon.  The
>> statement "16 bit sound can only be generated by the DSP" doesn't make
>> sense in this context (unless you have a bunch of resistors hanging
>> off it:)
>
>DSP's usually provide a serial interface that can be used to provide a
>bitstream to an audio DAC (CD style) or a CODEC (bi-directional A-D/D-A).
>
>Somewhere in the Atari system, there is sitting a DAC or CODEC, which
>we *might* assume is 16-bits and the DSP is probably directly interaced
>to it.
>
>There *might* be some other path that would let a DMA channel or CPU
>port dump 16-bit samples directly to/from such a DAC or CODEC, which would
>provide an alternative to the small sample memory of the DSP, but that is
>not implicit in the specs that have shown up here.
>
>What the specs do seem to imply is some kind of analog cross-point matrix
>for selecting between the different audio function blocks provided.
>
>This is not to say that the Atari implementation is "bad".  If there is
>and efficient interface between the processor side and DSP memory (not
>a given with many DSP's) that can let the processor or blitter use the
>DSP memory as a buffer, then extensive sampling is possible.
>
>If not, then the DSP still allows doing some pretty nice stuff with
>either waveform synthesis techniques or doing expansion of ADPCM or
>MPEG style compressed audio.


The Atari Falcon has a CODEC made by Philips/Sony.

R.A.W