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GUS Programmer's Digest Thu Jul 29 00:07 Volume 2: Issue 30
Today's Topics:
GUS Programmer's Digest V2 #29
SDK Doc Questions still
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: Wed, 28 Jul 93 14:45
From: "Thomas Gerstner"
Subject: Re: GUS Programmer's Digest V2 #29
Message-ID: <"93-07-28-14:45:50.68*UKBS">
Hmmm,
wie war das mit dem anrufen?
Ich wuerde sagen, wir treffen uns irgendwann bei Dir.
Ruf einfach mal an wenn Du zu Hause bist oder hinterlasse mir eine
Mail.
------------------------------
Date: Wed, 28 Jul 1993 12:11:07 -0700 (PDT)
From: roberts@brahms.amd.com (Dave Roberts)
Subject: SDK Doc Questions still
Message-ID: <9307281911.AA10717@angelo.amd.com>
I sent this message a few days ago and then left on vacation for a few
days. I expected to have my mailbox flooded with replys showing me
the way to wisdom and everlasting happiness. Instead I received
zilch. Sooo... here I go again. I you know the answer, please reply
to me personally or through the digest. Thanks.
Dave Roberts
david.roberts@amd.com
--------------------
I just snarfed the Postscript SDK documentation off the GUS
mailserver, along with the SDK itself. After reading the docs, I have
a few of questions.
First, a general comment: The theory of operation section of the
documentation needs to be expanded greatly! All the stuff that
follows later is pretty good, but there needs to be more discussion
about the format of sound data, loop points, volume envelopes, etc.
In other words, how all this stuff generally works. Much of this
stuff may be obvious to various people, but it wasn't for me. If I
hadn't been so engrossed with the GUS already, I'd have been totally
lost. Basically, the terminology wasn't defined (e.g., I was confused
between a start and a begin point on a wave for a while). Most of my
questions would be answered with an expanded general theory section.
Now, on to the real questions.
Question #1:
How does looping work? Specifically, how does reverse looping
operate? What are the end points? What are all the various looping
options? The docs mention resetting end points to deal with sampled
decays. What are the exact steps involved with this? How do you
handle decay without using a sampled decay? Just a volume ramp down
until you get to zero and then shut off the voice?
Question #2:
The voice control registers have bits that can be modified at any time
by the GF1. The GF1 does a read-modify-write cycle to update these
bits. The SDK docs say that when writing to a register containing one
of these bits that the software should write the value twice,
separated by a delay (which is specified by I don't remember). Anyway,
this is all fine and dandy, but imagine this situation.
Voice control reigster, bit 6, controls the direction of movement
through the wave. What if I (the program) want to update a bit in the
register. I read the register value, modify the bit I want, and write
it back twice. What if the GF1, between the program's writes changes
the direction of movement bit (because it was set to a loop mode and
hit the end of the loop points and is now bouncing back the other
way)? The problem that I see is that I (the program) will end up
setting the direction of movement bit back to the old value, which
will start the wave back bouncing the other way before it reaches the
other loop point. Am I right with this, or do I not understand
looping? Is this a problem? Is there a workaround other than, "don't
do that"?
Question #3:
One page 4 of the SDK docs they are describing volume ramping. There
is a table that describes the rate bits. The table mentions something
called a "FUR". What's a FUR?
Question #4:
What is the centerpoint for unsigned waveforms, 7F or 80 (hex)?
Thanks for any help you gurus might be able to give.
Dave Roberts
Advanced Micro Devices, Inc.
I/O and Network Products Division
david.roberts@amd.com
------------------------------
End of GUS Programmer's Digest V2 #30
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