SCUMM: Store sample rate in Mac MI1 / Loom savegames

This keeps the music from breaking when loading a savegame that was
made with a different sample rate than the current one. It also
breaks all savegames made in the past eight hours, but I don't think
it's necessary to maintain savegame compatibility within a pull
request, as long as it still works with savegames made before it.

2 files changed, 19 insertions, 8 deletions

diff --git a/engines/scumm/player_mac.cpp b/engines/scumm/player_mac.cpp
index cd1df51938..04c66c400c 100644
--- a/engines/scumm/player_mac.cpp
+++ b/engines/scumm/player_mac.cpp
@@ -107,16 +107,11 @@ void Player_Mac::saveLoadWithSerializer(Serializer *ser) {
 		}
 	} else {
 		static const SaveLoadEntry musicEntries[] = {
+			MKLINE(Player_Mac, _sampleRate, sleUint32, VER(94)),
 			MKLINE(Player_Mac, _soundPlaying, sleInt16, VER(94)),
 			MKEND()
 		};
 
-		// Note: This will fail slightly when loading a savegame if
-		// the mixer output rate has changed, because the pitch
-		// modifier and remaining samples were calculated from it. As
-		// a result, the first note to be played will be out of tune,
-		// and the channels will probably be slightly out of sync.
-
 		static const SaveLoadEntry channelEntries[] = {
 			MKLINE(Channel, _pos, sleUint16, VER(94)),
 			MKLINE(Channel, _pitchModifier, sleInt32, VER(94)),
@@ -132,6 +127,9 @@ void Player_Mac::saveLoadWithSerializer(Serializer *ser) {
 			MKEND()
 		};
 
+		uint32 mixerSampleRate = _sampleRate;
+		int i;
+
 		ser->saveLoadEntries(this, musicEntries);
 
 		if (ser->isLoading() && _soundPlaying != -1) {
@@ -141,9 +139,22 @@ void Player_Mac::saveLoadWithSerializer(Serializer *ser) {
 		}
 
 		ser->saveLoadArrayOf(_channel, _numberOfChannels, sizeof(Channel), channelEntries);
-		for (int i = 0; i < _numberOfChannels; i++) {
+		for (i = 0; i < _numberOfChannels; i++) {
 			ser->saveLoadEntries(&_channel[i], instrumentEntries);
 		}
+
+		if (ser->isLoading()) {
+			// If necessary, adjust the channel data to fit the
+			// current sample rate.
+			if (_soundPlaying != -1 && _sampleRate != mixerSampleRate) {
+				double mult = (double)_sampleRate / (double)mixerSampleRate;
+				for (i = 0; i < _numberOfChannels; i++) {
+					_channel[i]._pitchModifier = (int)((double)_channel[i]._pitchModifier * mult);
+					_channel[i]._remaining = (int)((double)_channel[i]._remaining / mult);
+				}
+			}
+			_sampleRate = mixerSampleRate;
+		}
 	}
 }
 
diff --git a/engines/scumm/player_mac.h b/engines/scumm/player_mac.h
index a30111bda0..0585eb16b0 100644
--- a/engines/scumm/player_mac.h
+++ b/engines/scumm/player_mac.h
@@ -69,7 +69,7 @@ private:
 	Common::Mutex _mutex;
 	Audio::Mixer *const _mixer;
 	Audio::SoundHandle _soundHandle;
-	const uint32 _sampleRate;
+	uint32 _sampleRate;
 	int _soundPlaying;
 
 	void stopAllSounds_Internal();