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 ************************************* To post to tomorrow's digest: To (un)subscribe or get help: To contact a human (last resort): FTP sites: archive.epas.utoronto.ca pub/pc/ultrasound wuarchive.wustl.edu systems/msdos/ultrasound Hints: - Get the FAQ from the FTP sites or the request server. - Mail to for info about other GUS related mailing lists (UNIX, OS/2, GUS-MIDI, etc.)