16 lines
1.7 KiB
Markdown
16 lines
1.7 KiB
Markdown
# kb's blog
|
||
|
||
random and not so random stuff/
|
||
**TinyMOD**
|
||
*Posted on 2011/10/23*
|
||
|
||
At some point in 2007 somebody told me how the Amiga’s sound chip, Paula, was able to modify a sound’s volume digitally without using multiplication – dedicated circuits for that would have been prohibitively expensive for a home computer in 1984: It simply has a 6-bit counter per voice that’s incremented every cycle and if its value is above the set volume, the voice is silenced for that cycle. So effectively it’s PWM with a pulse frequency of about 50Khz.
|
||
|
||
“But wait, shouldn’t that color the sound, ring modulation artifacts and such?” I thought. The answer is of course a resounding no (also all artifacts introduced by the PWM are outside the audible range) but that didn’t stop me from trying to emulate a Paula voice at the full 3.5MHz and then filtering it down to find out how it sounds.
|
||
|
||
Yeah well, and while we’re at it, let’s see if we can hack up a simple .MOD player too without using anything a 68000 didn’t have to offer (multiplications and such). Because coding for a couple of hours and the only being able to play a single waveform is boring.
|
||
|
||
Another few hours later there was one additional never-to-be-published toy project on my HD that way able to play a few MOD files that I liked, and that was about to be abandoned… if it hadn’t been for a thread on pouet.net where somebody was asking for a module player source. And I just came home from a party and was ever so slightly inebriated, so I just pasted the source code there. A discussion spawned, I cleaned up the code a bit and fixed some replay errors, and so here it is, released into the public domain for everyone to enjoy or laugh at:
|
||
|
||
Just add sound output. Have fun :)
|