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From: zech@leadsv.UUCP (Bill Zech)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Questions about Sound Blaster
Keywords: Sound Blaster
Message-ID: <12122@leadsv.UUCP>
Date: 12 Jul 90 01:28:09 GMT
References: <3414@sactoh0.UUCP> <13958@wpi.wpi.edu>
Reply-To: zech@leadsv.LEADS.LMSC.COM.UUCP (Bill Zech)
Distribution: usa
Organization: LMSC-LEADS, Sunnyvale, Ca.
Lines: 44

In article <13958@wpi.wpi.edu> dmorin@wpi.wpi.edu (Duane D Morin) writes:
>I would like to add what I consider a very important question to the list
>of CMS questions:  How dependent on RAM is the digitizing section of the
>board?  I have only a 640K machine, and I want to be able to sample at 
>least a few seconds of data for various sound effects.  Can I do this?  
>Do I need to keep my sounds in memory or do they get sent off to hard disk?
>Should I just scrap the deal and wait till I get a 2meg 286?
>
>DDM

The Sound Blaster uses a DMA channel to drive the DSP chip.  DMA
is simplest when it talks to RAM below the one meg line, so a 
640K system is fine.

DMA is transfered in blocks up to 64K.  That's about 64,000 samples
at 8-bit resolution, more if you have compressed the data using
the ADPCM (?) compression the SB suports in its DSP chip.  Lots
of digital sound files sound OK at about 11,000 samples/sec 
(you can vary the speed, of course), so
one full size DMA block can give you about 5-6 seconds.  When an
end of DMA transfer is detected by the DSP chip, it can interrupt
the PC on one of 4 IRQ lines.  The PC software (VOXKIT, etc.) may
then reprogram the DMA controller to transfer starting with a new
block.  This can be done as often as you have memory and/or can
fill it.

The SB and DMA channel do not support double buffering (ping-pong, 
if you will), so at the end of each block you will experience a 
small glitch while you start up the next block.  In practice, I
have not found this to be noticable.

Note that the IRQ line is only used in conjunction with the DSP
chip.  It is *not* used in playing music with either the Adlib
or CMS music channels.

I have converted various sound files from the MAC world to .VOC
files for the SB, and they sound fine.  There are quite a few located
on CIS.  For a variety of music files, sound effects, lines from 
movies and TV programs, try the MACFUN forum on CIS, and also
check the IBMNEW/music forum on CIS.  There is lots of stuff there.
I got a bunch this morning.

- Bill
CIS 73547,1034