SCI: Add a more generic solution for the problem found in bug #3605269

We now accept signals from all channels if channel 15 is missing. This
is a very rare edge case, but our behavior is now somewhat closer to what
the original interpreter seems to be doing. Mordack's appearance animation
is now synced properly. The more generic workaround works for songs 1840
and 1843, but not for 1849, which is still problematic and we still resort
to manually changing its dataInc selector

1 files changed, 9 insertions, 1 deletions

diff --git a/engines/sci/sound/midiparser_sci.cpp b/engines/sci/sound/midiparser_sci.cpp
index 4e54797960..0e5672460d 100644
--- a/engines/sci/sound/midiparser_sci.cpp
+++ b/engines/sci/sound/midiparser_sci.cpp
@@ -475,7 +475,13 @@ void MidiParser_SCI::parseNextEvent(EventInfo &info) {
 	case 0xC:
 		info.basic.param1 = *(_position._playPos++);
 		info.basic.param2 = 0;
-		if (info.channel() == 0xF) {// SCI special case
+		// Normally, song signalling events are sent through the special SCI
+		// channel 15. There are some songs where that special channel is
+		// missing completely, and the signals are sent through the other
+		// channels. Such a case is the Windows version of KQ5CD, songs 1840,
+		// 1843 and 1849 (bug #3605269). Therefore, we check if channel 15 is
+		// present, and if not, we accept signals from all other channels.
+		if (info.channel() == 0xF || !_channelUsed[15]) {	// SCI special channel
 			if (info.basic.param1 != kSetSignalLoop) {
 				// At least in kq5/french&mac the first scene in the intro has
 				// a song that sets signal to 4 immediately on tick 0. Signal
@@ -491,6 +497,8 @@ void MidiParser_SCI::parseNextEvent(EventInfo &info) {
 					_position._playTick || info.delta) {
 					_signalSet = true;
 					_signalToSet = info.basic.param1;
+					debugC(kDebugLevelSound, "Setting signal of song %d to %d from channel %d",
+							_pSnd->resourceId, _signalToSet, info.channel());
 				}
 			} else {
 				_loopTick = _position._playTick + info.delta;