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Cleaned up the comments in unkOutput2(), and added a big note about the bug

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where low-frequent noises are playing at the beginning of some new sounds.

svn-id: r21265
This commit is contained in:
Torbjörn Andersson 2006-03-13 23:05:11 +00:00
parent d66d7ff76b
commit 221263e275
1 changed files with 17 additions and 9 deletions
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26
engines/kyra/sound_adlib.cpp
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@ -757,7 +757,7 @@ void AdlibDriver::initChannel(Channel &channel) {
// normally here are nullfuncs but we set 0 for now
channel.primaryEffect = 0;
channel.secondaryEffect = 0;
channel.spacing1 = 0x01;
channel.spacing1 = 1;
}
void AdlibDriver::noteOff(Channel &channel) {
@ -784,26 +784,34 @@ void AdlibDriver::unkOutput2(uint8 chan) {
// I believe this has to do with channels 6, 7, and 8 being special
// when Adlib's rhythm section is enabled.
if (_unk4 && chan >= 6)
return;
uint8 offset = _regOffset[chan];
// Clear the Attack Rate / Decay Rate for the channel
// The channel is cleared: First the attack/delay rate, then the
// sustain/release rate, and finally the note is turned off.
writeOPL(0x60 + offset, 0xFF);
writeOPL(0x63 + offset, 0xFF);
// Clear the Sustain Level / Release Rate for the channel
writeOPL(0x80 + offset, 0xFF);
writeOPL(0x83 + offset, 0xFF);
// Octave / F-Number / Key-On
// Turn the note off, then turn it on again. This could be a "note on"
// function, but it also clears the octave and the part of the
// frequency (F-Number) stored in this register. Weird.
writeOPL(0xB0 + chan, 0x00);
// FIXME!
//
// ...and then the note is turned on again, with whatever value is
// still lurking in the A0 + chan register, but everything else -
// including the two most significant frequency bit, and the octave -
// set to zero.
//
// This is very strange behaviour, and appears to be the cause of the
// bug where low-frequent notes are played at the beginning of a new
// sound. However, this is what the original does here...
writeOPL(0xB0 + chan, 0x20);
}