[Coladam] About tone channels attenuation (volume) -and- digital sounds (RESULTS)

Ronald Mitchell bytehacker at tallcedarskennels.com
Thu Dec 10 20:48:21 CET 2009


Looks like you're really pushing the envelope Daniel.

It's been so long since I've done this, that I'm not even sure if what  
I'm about to say would make any sense..... but.... here goes

As I recall, it took a 10 bit transfer from Adam's memory to the sound  
chip to play a note. That 10 bits specified the voice, the pitch, and  
the volume (attenuation),  So the transfer of data to the sound chip  
had to be kicked out to the sound port with two successive bytes. Any  
particular note, once activated and given some value for attenuation  
would stay on until the programmer turned it off by sending the next  
note in the song.  If you sent the data to the noise voice, you could  
get some interesting sound effects (ie drum rhythms or arcade game  
noises)  simply by using the duration data to control how slow or how  
fast the noise occurred.

Based on what I can remember of how the sound chip works, it seems to  
me that adjusting the attenuation alone could produce some interesting  
effects. But how would you send data so that the voice channel being  
addressed would recognize it as attenuation data and not data to  
control the other parameters (ie voice number and pitch)?

Nonetheless it seems like you might be on to something.

Seek and ye shall find my son. Keep looking.


Ron Mitchell


On 9-Dec-09, at 11:26 PM, Daniel Bienvenu wrote:

> Well, my experimentations reveal :
>
> 1 - The table of values concerning all the possible attenuations for  
> a single channel is correct.
>
> 2 - The selection of my 64 values is somehow correct.
>
> 3 - The application of a 6-bit audio sample to a Coleco project is  
> possible.
>
> 4 - BUT THERE'S A GLITCHY PROBLEM.
>
>
> Well, pushing 3 attenuation values to the sound port when the  
> previous one is quite different but the result should me a volume  
> not far away, it generates glitches that sounds like low-volume high  
> pitch periodic noise in the background. But, the idea works... but  
> the resulting sound is "corrupted". I have to admit, I don't think  
> there is a way around the problem, specially if I keep the same  
> strategy. Well, that's not true, I didn't test sending attenuation  
> values backward, instead of FFF, FFE, FFC, FEA, etc., I'll try  
> FFF,EFF CFF, AEF. But I'm expecting the results to be at beat only  
> less noisy but still there.
>
> The best strategy should be to update only one tone channel all the  
> time. That puts me back into my previous digital sound system. But  
> there is a hope, and this time I'll test first and give feedback  
> later... If I don't forget to do so.
>
> Have a nice day!
>
> Daniel
>
>
>
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