[Scummvm-cvs-logs] SF.net SVN: scummvm: [21265] scummvm/trunk/engines/kyra/sound_adlib.cpp

[eriktorbjorn at users.sourceforge.net]

Revision: 21265
Author:   eriktorbjorn
Date:     2006-03-13 15:05:11 -0800 (Mon, 13 Mar 2006)
ViewCVS:  http://svn.sourceforge.net/scummvm/?rev=21265&view=rev

Log Message:
-----------
Cleaned up the comments in unkOutput2(), and added a big note about the bug
where low-frequent noises are playing at the beginning of some new sounds.

Modified Paths:
--------------
    scummvm/trunk/engines/kyra/sound_adlib.cpp
Modified: scummvm/trunk/engines/kyra/sound_adlib.cpp
===================================================================
--- scummvm/trunk/engines/kyra/sound_adlib.cpp	2006-03-13 21:38:20 UTC (rev 21264)
+++ scummvm/trunk/engines/kyra/sound_adlib.cpp	2006-03-13 23:05:11 UTC (rev 21265)
@@ -757,7 +757,7 @@
 	// 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 @@
 
 	// 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
+	writeOPL(0xB0 + chan, 0x00);
 
-	// 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.
+	// 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, 0x00);
 	writeOPL(0xB0 + chan, 0x20);
 }
 


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