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From: sam@amiga.UUCP (Samuel C. Dicker)
Newsgroups: net.micro.amiga
Subject: Re: Question about Amiga Sound/music capibilities
Message-ID: <990@amiga.amiga.UUCP>
Date: Tue, 15-Apr-86 06:29:42 EST
Article-I.D.: amiga.990
Posted: Tue Apr 15 06:29:42 1986
Date-Received: Thu, 17-Apr-86 01:15:54 EST
References: <1781@caip.RUTGERS.EDU>
Reply-To: sam@snidely.UUCP (Samuel C. Dicker)
Organization: Commodore-Amiga Inc., 983 University Ave #D, Los Gatos CA 95030
Lines: 85

In article <1781@caip.RUTGERS.EDU> mende@shire.decnet writes:

>  What are the synthesizer abilities of the Amiga?

Hardware:
---------

The Amiga has four 8 bit D/A converters.  Each D/A has a programmable
(by the 68000) volume and sampling rate (period) control.  They are wired
into 2 low-pass filters for the left and right stereo channels.  Each D/A
converter can be loaded by the 68000 or by it's own DMA channel.  Each audio
DMA channels can be used either to feed samples to it's D/A converter or to
set the volume and/or period of another D/A converter.  The DMA channels
automatically restart at the end of the buffer.

                               +---------------+
                               |               |
  +---------------+            | CHANNEL 0 D/A |------+
  | CHANNEL 0 DMA |-->O..__O-->|data           |      |
  +---------------+            +---------------+      |
                        O                             |
                         \     +---------------+      |   +----------+
                          `--->|vol&per        |      V   | LEFT     |
  +---------------+            | CHANNEL 1 D/A |--+   +-->| LOW-PASS |--> L OUT
  | CHANNEL 1 DMA |-->O..__O-->|data           |  |   ^   | FILTER   |
  +---------------+            +---------------+  |   |   +----------+
                        O                         |   |
                         \     +---------------+  |   |   +----------+
                          `--->|vol&per        |  V   |   | RIGHT    |
  +---------------+            | CHANNEL 2 D/A |->+-- | ->| LOW-PASS |--> R OUT
  | CHANNEL 2 DMA |-->O..__O-->|data           |      |   | FILTER   |
  +---------------+            +---------------+      |   +----------+
                        O                             |
                         \     +---------------+      |
                          `--->|vol&per        |      |
  +---------------+            | CHANNEL 3 D/A |------+
  | CHANNEL 3 DMA |-->O..__O-->|data           |
  +---------------+            +---------------+
                        O
                         \
			  `-- not used

   specs:

   DMA channels -    addressing range:         0 thru 0x7FFFF (word aligned)
                     buffer size range:        2 thru 131072 samples (even)
                     maximum rate:             28867.3 samples per second
                     
   D/A converters -  amplitude range:          -128 thru 127
                     amplitude accuracy:       < 1/2 least significant bit
                     sampling rate range:      279.365 ns thru 18.3085 ms
                     sampling rate resolution: 279.365 ns
                     volume control range:     0 thru 64 linear

   low-pass filters- slope:                    6 pole, 36db/octave
                     pass band response:       + or - 3db 15Hz thru 4kHz
                     stop band response:       -40db at 7kHz


Software:
---------

ROM kernal audio is an exec device.  Commands include allocation and
arbitration (prioritized stealing) of channels, and DMA channel control.

>  Does it have 4 or 6 parameter envelope generator?
Envelopes are generated by the application software and can have any number
of parameters or a custom envelope table lookup.

>  What are the basic waveforms?
Anything you want. :-)

>  Does it come with complex waveform generation by additive
>  harmonic synthesis?
The audio device (in the ROM kernal) supports but does not provide any type
of synthesis.  I would be glad to answer any question about how to do any
(your favorite) type of synthesis on the Amiga.

>  What type of MIDI data does it handle.
The serial port on the Amiga can be set to run at MIDI rate (31250 baud) and
with a little level conversion, opto-isolation and buffering the Amiga can
send and receive MIDI; however, no MIDI driver is provided in the ROM kernal.

Sam Dicker
{decwrl|hplabs}!pyramid!amiga!sam