opl: Handle negative time division values.

A negative time division file indicates the MIDI file uses SMPTE time
rather than the normal time system. This is not supported yet, but for
the time being, return a sensible time division value that doesn't
cause the sound to stutter and the game to become unplayable.

This fixes #352, although the affected MIDIs do not yet play properly.

1 files changed, 13 insertions, 1 deletions

diff --git a/src/midifile.c b/src/midifile.c
index 6e40a274..94ec4441 100644
--- a/src/midifile.c
+++ b/src/midifile.c
@@ -699,7 +699,19 @@ int MIDI_GetNextEvent(midi_track_iter_t *iter, midi_event_t **event)
 
 unsigned int MIDI_GetFileTimeDivision(midi_file_t *file)
 {
-    return SHORT(file->header.time_division);
+    short result = SHORT(file->header.time_division);
+
+    // Negative time division indicates SMPTE time and must be handled
+    // differently.
+    if (result < 0)
+    {
+        // TODO: Figure this out.
+        return 96;
+    }
+    else
+    {
+        return result;
+    }
 }
 
 void MIDI_RestartIterator(midi_track_iter_t *iter)