Re: Sega sound boards...

On Wed, 3 Dec 1997 13:52:28 -0800, Clay Cowgill <clayc@diamondmm.com>
wrote:

>>Space Fury 8 bit 22khz 1.2mb
>>Star Trek 8 bit 22khz 1.0mb
>>Zektor 8 bit 22khz 1.2mb
>>
>>the samples were created at 48khz 16bits and bandpass
>>filtered prior to sample rate converison
>
>They're all just voice-band stuff, no? Anyone have a convincing reason why
>I couldn't resample these to 8KHz? (I don't recall the frequency response
>of the SPO-250, but I doubt it's over 4KHz-- and even if it is, human voice
>energy rolls off real fast past 1.6KHz...)
>
>If I can fit 'em into 1Mbyte or less a "sample player" card is kind-of a
>no-brainer. (1Mbyte is my max "pain threshold" for EPROMs now-a-days.)
>Simple RLE compression would probably do pretty well on the samples too...)

Nah, it works like sh*t, unless there is a lot of "true" silences (even
the slightest noise keeps RLE from working).

You might try ADPCM, go download the examples on the Microchip home
page. They use a version of ADPCM that uses no floating point. As long
as you stick to voice, ADPCM works well. Just don't try pumping any
music through it.

>I'm thinking of a 2051 controller with 2 27C040's, 4 74ls193's, a DAC and
>some glue logic... The controller gets the sample commands from the G-80
>I/O port, then parallel loads the start address of the appropriate sample
>in the cascaded counters (193's). Then with each strobe of an I/O line on
>the 2051 to the counters we get a new byte of sample data which can be
>decompressed and output to a DAC (just an R2R ladder with an output filter
>is probably fine).

At these speed PWM works really well, is much cheaper, and using a
processor dedicated to the job, could most likely be done completely in
software. Though a 10bit PWM port like that in the PIC makes life easy.
Once again refer to the PIC technote -- a fully functional speech
synthesizer -- complete with schematic and source code. It might be
just what you're looking for, as is. They even have PC based "C"
software for creating the compressed image. All the work is done for
you!

-Zonn

<><><><><><><><><><><><><><><><><><><><><><><><><><><><

 ------ ___ Member of A.A.C.S.:
 |---- | ( ) Association for Artistically
    / / ( () ) Challenged Signatures
   / / //\\ // (__)
  / ---/ // \\ //\\ // zonn @ zonn . com
 -------| // \\/
Received on Wed Dec 3 14:31:10 1997