[Scummvm-cvs-logs] SF.net SVN: scummvm: [21197] scummvm/trunk/engines/kyra/sound_adlib.cpp

[eriktorbjorn at users.sourceforge.net]

Revision: 21197
Author:   eriktorbjorn
Date:     2006-03-10 00:19:53 -0800 (Fri, 10 Mar 2006)
ViewCVS:  http://svn.sourceforge.net/scummvm/?rev=21197&view=rev

Log Message:
-----------
Since updateAndOutput2() is the only function that sets up wave forms and
stuff, it pretty much has to be our "set instrument" function. Also, while I'm
not entirely sure of the implications, "unk23" is the Algorithm bit for the
Feedback / Algorithm register, so I've renamed it "algorithm".

Modified Paths:
--------------
    scummvm/trunk/engines/kyra/sound_adlib.cpp
Modified: scummvm/trunk/engines/kyra/sound_adlib.cpp
===================================================================
--- scummvm/trunk/engines/kyra/sound_adlib.cpp	2006-03-10 07:56:22 UTC (rev 21196)
+++ scummvm/trunk/engines/kyra/sound_adlib.cpp	2006-03-10 08:19:53 UTC (rev 21197)
@@ -127,7 +127,7 @@
 		uint8 unk24;
 		uint8 unk25;
 		uint8 unk28;
-		uint8 unk23;
+		uint8 algorithm;
 		uint8 unk39;	
 		uint8 unk40;
 		uint8 unk3;
@@ -157,7 +157,7 @@
 	void update1(uint8 unk1, OutputState &state);
 
 	void updateAndOutput1(uint8 rawNote, OutputState &state, bool flag = false);
-	void updateAndOutput2(uint8 unk1, uint8 *dataptr, OutputState &state);
+	void setInstrument(uint8 regOffset, uint8 *dataptr, OutputState &state);
 	void updateAndOutput3(OutputState &state);
 
 	void adjustVolume(OutputState &state);
@@ -771,38 +771,48 @@
 	writeOPL(0xB0 + _curTable, state.regBx);
 }
 
-void AdlibDriver::updateAndOutput2(uint8 unk1, uint8 *dataptr, OutputState &state) {
-	debugC(9, kDebugLevelSound, "updateAndOutput2(%d, %p, %d)", unk1, (const void *)dataptr, &state - _outputTables);
+void AdlibDriver::setInstrument(uint8 regOffset, uint8 *dataptr, OutputState &state) {
+	debugC(9, kDebugLevelSound, "setInstrument(%d, %p, %d)", regOffset, (const void *)dataptr, &state - _outputTables);
 	// Amplitude Modulation / Vibrato / Envelope Generator Type /
 	// Keyboard Scaling Rate / Modulator Frequency Multiple
-	writeOPL(0x20 + unk1, *dataptr++);
-	writeOPL(0x23 + unk1, *dataptr++);
+	writeOPL(0x20 + regOffset, *dataptr++);
+	writeOPL(0x23 + regOffset, *dataptr++);
 
 	uint8 temp = *dataptr++;
 
 	// Feedback / Algorithm
+
+	// It is very likely that _curTable really does refer to the same
+	// channel as regOffset, but there's only one Cx register per channel.
+
 	writeOPL(0xC0 + _curTable, temp);
 
-	state.unk23 = temp & 1;
+	// The algorithm bit. I don't pretend to understand this fully, but
+	// "If set to 0, operator 1 modulates operator 2. In this case,
+	// operator 2 is the only one producing sound. If set to 1, both
+	// operators produce sound directly. Complex sounds are more easily
+	// created if the algorithm is set to 0."
 
+	state.algorithm = temp & 1;
+
 	// Waveform Select
-	writeOPL(0xE0 + unk1, *dataptr++);
-	writeOPL(0xE3 + unk1, *dataptr++);
+	writeOPL(0xE0 + regOffset, *dataptr++);
+	writeOPL(0xE3 + regOffset, *dataptr++);
 
 	state.unk24 = *dataptr++;
 	state.unk25 = *dataptr++;
 
 	// Level Key Scaling / Total Level
-	writeOPL(0x40 + unk1, calculateLowByte1(state));
-	writeOPL(0x43 + unk1, calculateLowByte2(state));
+	writeOPL(0x40 + regOffset, calculateLowByte1(state));
+	writeOPL(0x43 + regOffset, calculateLowByte2(state));
 
 	// Attack Rate / Decay Rate
-	writeOPL(0x60 + unk1, *dataptr++);
-	writeOPL(0x63 + unk1, *dataptr++);
+	writeOPL(0x60 + regOffset, *dataptr++);
+	writeOPL(0x63 + regOffset, *dataptr++);
 
 	// Sustain Level / Release Rate
-	writeOPL(0x80 + unk1, *dataptr++);
-	writeOPL(0x83 + unk1, *dataptr++);
+	writeOPL(0x80 + regOffset, *dataptr++);
+	writeOPL(0x83 + regOffset, *dataptr++);
 }
 
 void AdlibDriver::updateAndOutput3(OutputState &state) {
@@ -825,7 +835,7 @@
 
 	// Level Key Scaling / Total Level
 	writeOPL(0x43 + _outputTable[_curTable], lowByte);
-	if (state.unk23) {
+	if (state.algorithm) {
 		lowByte = calculateLowByte1(state);
 
 		// Level Key Scaling / Total Level
@@ -916,7 +926,7 @@
 
 uint8 AdlibDriver::calculateLowByte1(OutputState &state) {
 	int8 value = state.unk24 & 0x3F;
-	if (state.unk23) {
+	if (state.algorithm) {
 		value += state.unk26;
 		value += state.unk27;
 		value += state.unk28;
@@ -1077,7 +1087,7 @@
 int AdlibDriver::updateCallback17(uint8 *&dataptr, OutputState &state, uint8 value) {
 	uint8 *ptr = _soundData;
 	ptr += READ_LE_UINT16(_soundData + (value << 1) + 0x1F4);
-	updateAndOutput2(_unkOutputByte1, ptr, state);
+	setInstrument(_unkOutputByte1, ptr, state);
 	return 0;
 }
 
@@ -1353,7 +1363,7 @@
 	_unkOutputByte1 = _outputTable[6];
 
 	_unkValue6 = *(ptr + 6);
-	updateAndOutput2(_unkOutputByte1, ptr, state);
+	setInstrument(_unkOutputByte1, ptr, state);
 
 	entry = *dataptr++ << 1;
 	ptr = _soundData + READ_LE_UINT16(_soundData + entry + 0x1F4);
@@ -1363,7 +1373,7 @@
 
 	_unkValue7 = entry = *(ptr + 5);
 	_unkValue8 = entry = *(ptr + 6);
-	updateAndOutput2(_unkOutputByte1, ptr, state);
+	setInstrument(_unkOutputByte1, ptr, state);
 
 	entry = *dataptr++ << 1;
 	ptr = _soundData + READ_LE_UINT16(_soundData + entry + 0x1F4);
@@ -1373,7 +1383,7 @@
 
 	_unkValue9 = entry = *(ptr + 5);
 	_unkValue10 = entry = *(ptr + 6);
-	updateAndOutput2(_unkOutputByte1, ptr, state);
+	setInstrument(_unkOutputByte1, ptr, state);
 
 	// Octave / F-Number / Key-On for channels 6, 7 and 8
 


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