Fix for Bug [817871]: Added MT-32 master volume adjustment to pause().

svn-id: r10759

1 files changed, 16 insertions, 1 deletions

diff --git a/scumm/imuse.cpp b/scumm/imuse.cpp
index a1fd7dddf6..826def887a 100644
--- a/scumm/imuse.cpp
+++ b/scumm/imuse.cpp
@@ -1200,7 +1200,7 @@ void IMuseInternal::initMT32(MidiDriver *midi) {
 	byte checksum = 0;
 	for (int i = 4; i < 27; ++i)
 		checksum -= buffer[i];
-	buffer[27] = checksum;
+	buffer[27] = checksum & 0x7F;
 	midi->sysEx(buffer, 28);
 	g_system->delay_msecs (500);
 
@@ -1224,12 +1224,27 @@ void IMuseInternal::init_queue() {
 }
 
 void IMuseInternal::pause(bool paused) {
+	if (_paused == paused)
+		return;
 	int vol = _music_volume;
 	if (paused)
 		_music_volume = 0;
 	update_volumes();
 	_music_volume = vol;
 
+	// Kill master volume on the MT-32, because for some
+	// reason the MT-32 often fails to respond to the
+	// channel volume update for a single channel.
+	// (Ref Bug #817871. Reportedly happens in the
+	// original distro, too.)
+	if (_midi_native && _native_mt32) {
+		byte buffer[8];
+		memcpy(buffer, "\x41\x10\x16\x10\x00\x16", 6);
+		buffer[6] = paused ? 0 : 100;
+		buffer[7] = (0 - 0x10 - 0x16 - buffer[6]) & 0x7F; // Checksum
+		_midi_native->sysEx (buffer, 8);
+	}
+
 	_paused = paused;
 }