Apparently-To: john.smith@gravis.com


GUS Programmer's Digest     Thu, 10 Mar 94 16:33 PST     Volume 9: Issue  26  

Today's Topics:
                               clipping
                    GUS Programmer's Digest V9 #25
                       Just a few questions....
                        Programming Tremelo...
                              ps-format

Standard Info:
	- Meta-info about the GUS can be found at the end of the Digest.
	- Before you ask a question, please READ THE FAQ.

----------------------------------------------------------------------

Date: Thu, 10 Mar 1994 14:42:49 -0500
From: gord@smos.bc.ca (Gord Wait S-MOS Systems Vancouver Design Center)
Subject: Re: clipping

<Talk about gus clipping compared to analog clipping removed>

"VISX80::GRECNER" <GRECNER%VISX80.decnet@musx53.zfe.siemens.de>
writes:
>I can't agree here. Analog mixers have much greater dynamic range. It's
>not the same result if I reduce 16-bit sample to 8-bits and if I turn
>the mix volume on an analog synth down to get the same dB effect.
>In digital you are dealing with discrete levels, the only problem in
>analog is the linear distortion and noise, which is minimized in
>good devvices.

I can't agree here either!

It's been a while since I looked at analog audio mixers, but from what I
remember, getting an audio mixer that could take 16 channels of 96db
dynamic range and mixing them down to one without clipping would cost an arm
and a leg! Does such a high quality mixer exist at any cost?

16 bit audio has much more "headroom" than most cheaper mixers, 
in a single channel, never mind being able to mix more than one
such channel together. 

To bore you with the math behind it:

dynamic range = 20 * Log(10) of (Loudest signal/quietest signal)

16 bit dynamic range = 20 * Log(10)  (65536/1) = 96.33 db
65536 is the largest number you get from a 16 bit value.

8 bit dynamic range = 20 * Log(10) (256/1) = 48.16 db

Analog equivalent:

Assume a 2 volt maximum signal, then the quietest signal
would have to be: 2 volts / 65536 = 30.52 microvolts. 
T30.52 microvolts is incredibly low, and would be well below
the noise floor for most audio gear. 

I once worked on a Sony/MCI 16 channel multitrack mixer that
had custom op amps that used +- 24 volt power supplies to give more
headroom. TO have 96 db of dynamic range, it's noise would have to be
below (48 volts / 65536) = 131 millivolts, which is easier to achieve
than 30 microvolts. In it's day, this mixer was considered "pro recording
studio quality". (IE cost buckets more than consumer grade stuff.)

Back to work!

Gord Wait 	S-MOS Systems Vancouver Design Centre
                (B.C. Canada eh!)
gord@smos.bc.ca 

------------------------------

Date: Thu, 10 Mar 1994 12:32:37 +1000 (EST)
From: s921880@minyos.xx.rmit.EDU.AU (Adam Craig Seychell)
Subject: Re: GUS Programmer's Digest V9 #25

With all this talk about the voice mixing on the GUS and the dynamic range
of each voice, some of you might be interested in a little program that I
have written. This program will let you play a sine, pulse, sawtooth,
triangle, white noise  waveform on 23 voices and using the keyboard to
controll the volume, pan and frequency for each voice.  Anyone who would
like a copy then just email me. The ASM source is also avalable on request.
By using this program with all the voices active and volumes flat out it
will demonstrate the clipping effect.

------------------------------

Date: Thu, 10 Mar 1994 16:45:13 -0500 (EST)
From: Philip Andrew Nemec <blackdiamond+@CMU.EDU>
Subject: Re: Just a few questions....

> (My GUS is hooked up to a ProLogic Surround reciever)

Yeah - so is mine...  I made a program to generate sine waves for L, R,
Center, and Surround - pretty cool.  Anyway, if you start the same
sample playing REALLY soon after you started the other one you are
making them out of phase with each other - so the sound gets moved to
the rear.  That is a side effect that you don't want to get rid of -
just don't start the next sample quite as fast...

------------------------------

Date: Wed, 9 Mar 1994 16:46:29 +0800 (PST)
From: Francis Li <fli@nermal.santarosa.edu>
Subject: Programming Tremelo...

Is there a specific way to impliment tremolo using the GUSDK?  I have
experimented with the ramp volume procedures, but I can't get the right
effect.

Also, I know that there are tables missing for tremolo in the SDK, and I
know they have been posted before, can anyone tell me which file to d-load
on epas that has it?  Or can they be posted again?

------------------------------

Date: Wed, 9 Mar 1994 15:51:42 -1
From: KARL ERIK ASBJcRNSEN <KARLEA@stud.sarpih.no>
Subject: ps-format

This has nothing to do with GUS, but a friend of mine has the GUS-sdk 
packed down in  PS-format. Anyone knows how to un-PS?

Thanks...

+------------------------------------------+
| Karl Erik Asbjornsen                     |
| EMAIL: karlea@stud.sarpih.no             |
| Snailmail: Raakilvn 49, N-1710 Sarpsborg |
| IRC: bare                                |
+------------------------------------------+

------------------------------

End of GUS Programmer's Digest V9 #26
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