SCUMM: Fix volume levels when playing SFX and music at the same time in AD player.

This sadly decreases the granularity of volume control since AdLib has far
less distinct volume levels as we. However, having music and sfx at the same
time increases the overall experience.

2 files changed, 50 insertions, 14 deletions

diff --git a/engines/scumm/players/player_ad.cpp b/engines/scumm/players/player_ad.cpp
index 16e03d1131..6225efeaeb 100644
--- a/engines/scumm/players/player_ad.cpp
+++ b/engines/scumm/players/player_ad.cpp
@@ -77,6 +77,8 @@ Player_AD::Player_AD(ScummEngine *scumm, Audio::Mixer *mixer)
 	for (int i = 0; i < ARRAYSIZE(_voiceChannels); ++i) {
 		_voiceChannels[i].hardwareChannel = -1;
 	}
+
+	_musicVolume = _sfxVolume = 255;
 }
 
 Player_AD::~Player_AD() {
@@ -98,6 +100,9 @@ void Player_AD::setMusicVolume(int vol) {
 void Player_AD::startSound(int sound) {
 	Common::StackLock lock(_mutex);
 
+	// Setup the sound volume
+	setupVolume();
+
 	// Query the sound resource
 	const byte *res = _vm->getResourceAddress(rtSound, sound);
 
@@ -135,9 +140,6 @@ void Player_AD::startSound(int sound) {
 			_vm->_res->lock(rtSound, sound);
 		}
 	}
-
-	// Setup the sound volume
-	setupVolume();
 }
 
 void Player_AD::stopSound(int sound) {
@@ -222,22 +224,20 @@ int Player_AD::readBuffer(int16 *buffer, const int numSamples) {
 
 void Player_AD::setupVolume() {
 	// Setup the correct volume
-	int soundVolumeMusic = CLIP<int>(ConfMan.getInt("music_volume"), 0, Audio::Mixer::kMaxChannelVolume);
-	int soundVolumeSfx = CLIP<int>(ConfMan.getInt("sfx_volume"), 0, Audio::Mixer::kMaxChannelVolume);
+	_musicVolume = CLIP<int>(ConfMan.getInt("music_volume"), 0, Audio::Mixer::kMaxChannelVolume);
+	_sfxVolume = CLIP<int>(ConfMan.getInt("sfx_volume"), 0, Audio::Mixer::kMaxChannelVolume);
+
 	if (ConfMan.hasKey("mute")) {
 		if (ConfMan.getBool("mute")) {
-			soundVolumeMusic = 0;
-			soundVolumeSfx = 0;
+			_musicVolume = 0;
+			_sfxVolume = 0;
 		}
 	}
 
-	// In case a music is being played set the music volume. Set the sfx
-	// volume otherwise. This is safe because in the latter case either
-	// sfx are playing or there is no sound being played at all.
-	if (_soundPlaying != -1) {
-		_mixer->setChannelVolume(_soundHandle, soundVolumeMusic);
-	} else {
-		_mixer->setChannelVolume(_soundHandle, soundVolumeSfx);
+	// Update current output levels
+	for (int i = 0; i < ARRAYSIZE(_operatorOffsetTable); ++i) {
+		const uint reg = 0x40 + _operatorOffsetTable[i];
+		writeReg(reg, readReg(reg));
 	}
 }
 
@@ -287,10 +287,42 @@ void Player_AD::limitHWChannels(int newCount) {
 	_numHWChannels = newCount;
 }
 
+const int Player_AD::_operatorOffsetToChannel[22] = {
+	 0,  1,  2,  0,  1,  2, -1, -1,
+	 3,  4,  5,  3,  4,  5, -1, -1,
+	 6,  7,  8,  6,  7,  8
+};
+
 void Player_AD::writeReg(int r, int v) {
 	if (r >= 0 && r < ARRAYSIZE(_registerBackUpTable)) {
 		_registerBackUpTable[r] = v;
 	}
+
+	// Handle volume scaling depending on the sound type.
+	if (r >= 0x40 && r <= 0x55) {
+		const int operatorOffset = r - 0x40;
+		const int channel = _operatorOffsetToChannel[operatorOffset];
+		if (channel != -1) {
+			const bool twoOPOutput = (readReg(0xC0 + channel) & 0x01) != 0;
+
+			int scale = Audio::Mixer::kMaxChannelVolume;
+			// We only scale the volume of operator 2 unless both operators
+			// are set to directly produce sound.
+			if (twoOPOutput || operatorOffset == _operatorOffsetTable[channel * 2 + 1]) {
+				if (_hwChannels[channel].sfxOwner) {
+					scale = _sfxVolume;
+				} else {
+					scale = _musicVolume;
+				}
+			}
+
+			int vol = 0x3F - (v & 0x3F);
+			vol = vol * scale / Audio::Mixer::kMaxChannelVolume;
+			v &= 0xA0;
+			v |= (0x3F - vol);
+		}
+	}
+
 	_opl2->writeReg(r, v);
 }
 
diff --git a/engines/scumm/players/player_ad.h b/engines/scumm/players/player_ad.h
index fbf604e3f8..0a0ba8aba1 100644
--- a/engines/scumm/players/player_ad.h
+++ b/engines/scumm/players/player_ad.h
@@ -68,7 +68,10 @@ private:
 	Audio::Mixer *const _mixer;
 	const int _rate;
 	Audio::SoundHandle _soundHandle;
+
 	void setupVolume();
+	int _musicVolume;
+	int _sfxVolume;
 
 	OPL::OPL *_opl2;
 
@@ -88,6 +91,7 @@ private:
 		SfxSlot *sfxOwner;
 	} _hwChannels[9];
 	int _numHWChannels;
+	static const int _operatorOffsetToChannel[22];
 
 	int allocateHWChannel(int priority, SfxSlot *owner = nullptr);
 	void freeHWChannel(int channel);