[Coladam] More about tone channels attenuation (volume) -and- digital sounds (PART 2)

Daniel Bienvenu newcoleco at yahoo.fr
Fri Dec 11 15:44:44 CET 2009


Hello D.Vik,

Well, your version sounds much better. I don't understand yet how it's encoded exactly, but it sounds impressive. I did read about the subject at least twice in the msx forum.

http://www.dvik-joyrex.com/development/pcmtest.zip

Question : Can you reduce the rom file a little bit?


I don't know if it's the same thing for you... I've tested with bluemsx and the real thing, and it was really slower with the real console than bluemsx... could it be because of the video part can slow down the execution? I did experiment this situation with a Commodore 64 long time ago.


A last thing before going to sleep, I've tested 2 possibilities so far for a compression and this is what I've got :

1 - 11K : Using nibbles (4bit) into bytes gives the ROM size predicted (approx 11K) but the player is now more slower ... to be optimized.

2 - 18K : Using a 5bit format leaves a wasted 3bit per byte. I've decided to try a primitive RLE compression. The compression result is not impressive but the sound quality is somewhere between the 6bit and the 4bit versions. Unfortunately, the player is not only slower but too slow; I'll think of something to solve that problem... I hope.


I've calculated and using 4 6bit values into 3 bytes gives also something near 18K. It's a possibility.


Note: Maybe it's clear now that what I'm trying to do is to improve my devkit which is still under developments. My good old sound tool that deals with digital sounds did gives nice results but I knew it can be improved and the idea I had by analyzing the tone channel attenuations helped me to think about a possibility, a good compromise between quality and rom space. How can I increase the sound quality without adding too much data in the process? That's the question I wanted to answer. My goal is not to make the best sound quality ever, but to get something that can fit the needs within a standard coleco.


Have a nice day!

Daniel


      


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