From 495694da29ff736fba2fdc696553ee7197247174 Mon Sep 17 00:00:00 2001
From: Simon Howard
Date: Sat, 10 May 2014 14:00:41 -0400
Subject: opl: Add API to adjust tempo.

When the tempo is changed, the times on all active timers must be
adjusted to match the new timing values. Add an API to do this and
invoke it when a tempo change meta event is read.
---
 src/i_oplmusic.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

(limited to 'src')

diff --git a/src/i_oplmusic.c b/src/i_oplmusic.c
index f38e7162..489b6d55 100644
--- a/src/i_oplmusic.c
+++ b/src/i_oplmusic.c
@@ -1016,6 +1016,12 @@ static void PitchBendEvent(opl_track_data_t *track, midi_event_t *event)
     }
 }
 
+static void MetaSetTempo(unsigned int tempo)
+{
+    OPL_AdjustCallbacks((float) us_per_beat / tempo);
+    us_per_beat = tempo;
+}
+
 // Process a meta event.
 
 static void MetaEvent(opl_track_data_t *track, midi_event_t *event)
@@ -1041,7 +1047,7 @@ static void MetaEvent(opl_track_data_t *track, midi_event_t *event)
         case MIDI_META_SET_TEMPO:
             if (data_len == 3)
             {
-                us_per_beat = (data[0] << 16) | (data[1] << 8) | data[2];
+                MetaSetTempo((data[0] << 16) | (data[1] << 8) | data[2]);
             }
             break;
 
@@ -1168,19 +1174,19 @@ static void TrackTimerCallback(void *arg)
 static void ScheduleTrack(opl_track_data_t *track)
 {
     unsigned int nticks;
-    unsigned int ms;
-    static int total = 0;
+    uint64_t ms;
 
     // Get the number of milliseconds until the next event.
 
     nticks = MIDI_GetDeltaTime(track->iter);
-    ms = (nticks * us_per_beat * TEMPO_FUDGE_FACTOR) / ticks_per_beat;
-    total += ms;
+    ms = nticks;
+    ms *= us_per_beat * TEMPO_FUDGE_FACTOR;
+    ms /= ticks_per_beat;
 
     // Set a timer to be invoked when the next event is
     // ready to play.
 
-    OPL_SetCallback(ms, TrackTimerCallback, track);
+    OPL_SetCallback((unsigned int) ms, TrackTimerCallback, track);
 }
 
 // Initialize a channel.
-- 
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