Fix MIDI timestamp calculations when you loop AND have time track...

... At least it fixes the gross problem; but there seems to be a small
accumulation of error still each time around the loop, that I don't understand
yet.

src/AudioIO.cpp

@@ -214,7 +214,8 @@
   special "event" of sending all notes off. After that, we destroy
   the iterator and use PrepareMidiIterator() to set up a NEW one.
   At each iteration, time must advance by (mT1 - mT0), so the
-  accumulated time is held in mMidiLoopOffset.
+  accumulated complete loop time (in "unwarped," track time) is computed
+  by MidiLoopOffset().
 
   \todo run through all functions called from audio and portaudio threads
   to verify they are thread-safe. Note that synchronization of the style:
@@ -2144,7 +2145,7 @@ bool AudioIO::StartPortMidiStream()
    if (mLastPmError == pmNoError) {
       mMidiStreamActive = true;
       mMidiPaused = false;
-      mMidiLoopOffset = 0;
+      mMidiLoopPasses = 0;
       mMidiOutputComplete = false;
       PrepareMidiIterator();
 
@@ -3804,6 +3805,19 @@ void AudioIO::SetListener(AudioIOListener* listener)
 static Alg_update gAllNotesOff; // special event for loop ending
 // the fields of this event are never used, only the address is important
 
+double AudioIO::UncorrectedMidiEventTime()
+{
+   double time;
+   if (mTimeTrack)
+      time =
+         mTimeTrack->ComputeWarpedLength(mT0, mNextEventTime - MidiLoopOffset())
+            + mT0 + (mMidiLoopPasses * mWarpedLength);
+   else
+      time = mNextEventTime;
+
+   return time + PauseTime();
+}
+
 void AudioIO::OutputEvent()
 {
    int channel = (mNextEvent->chan) & 0xF; // must be in [0..15]
@@ -3811,13 +3825,10 @@ void AudioIO::OutputEvent()
    int data1 = -1;
    int data2 = -1;
 
-   double eventTime;
+   double eventTime = UncorrectedMidiEventTime();
-   if (mTimeTrack)
+
-      eventTime = mTimeTrack->ComputeWarpedLength(mT0, mNextEventTime) + mT0;
-   else
-      eventTime = mNextEventTime;
    // 0.0005 is for rounding
-   double time = eventTime + PauseTime() + 0.0005 -
+   double time = eventTime + 0.0005 -
                  ((mMidiLatency + mSynthLatency) * 0.001);
 
    time += 1; // MidiTime() has a 1s offset
@@ -3833,8 +3844,8 @@ void AudioIO::OutputEvent()
       AllNotesOff();
       if (mPlayMode == gAudioIO->PLAY_LOOPED) {
          // jump back to beginning of loop
-         mMidiLoopOffset += (mT1 - mT0);
+         ++mMidiLoopPasses;
-         PrepareMidiIterator(false, mMidiLoopOffset);
+         PrepareMidiIterator(false, MidiLoopOffset());
       } else {
          mNextEvent = NULL;
       }
@@ -3958,18 +3969,19 @@ void AudioIO::GetNextEvent()
         mNextEvent = NULL;
         return;
    }
+   auto midiLoopOffset = MidiLoopOffset();
    mNextEvent = mIterator->next(&mNextIsNoteOn,
                                 (void **) &mNextEventTrack,
-                                &nextOffset, mT1 + mMidiLoopOffset);
+                                &nextOffset, mT1 + midiLoopOffset);
 
-   mNextEventTime  = mT1 + mMidiLoopOffset + 1;
+   mNextEventTime  = mT1 + midiLoopOffset + 1;
    if (mNextEvent) {
       mNextEventTime = (mNextIsNoteOn ? mNextEvent->time :
                               mNextEvent->get_end_time()) + nextOffset;;
    } 
-   if (mNextEventTime > (mT1 + mMidiLoopOffset)){ // terminate playback at mT1
+   if (mNextEventTime > (mT1 + midiLoopOffset)){ // terminate playback at mT1
       mNextEvent = &gAllNotesOff;
-      mNextEventTime = mT1 + mMidiLoopOffset - ALG_EPS;
+      mNextEventTime = mT1 + midiLoopOffset - ALG_EPS;
       mNextIsNoteOn = true; // do not look at duration
       mIterator->end();
       mIterator.reset(); // debugging aid
@@ -4000,12 +4012,10 @@ void AudioIO::FillMidiBuffers()
          break;
       }
    SetHasSolo(hasSolo);
-   // Compute the current track time differently depending upon
+   double time = AudioTime();
-   // whether audio playback is in effect:
-   double time = AudioTime() - PauseTime();
    while (mNextEvent &&
-          (mTimeTrack ? (mTimeTrack->ComputeWarpedLength(mT0, mNextEventTime) + mT0) : mNextEventTime)
+          UncorrectedMidiEventTime() <
-             < time + ((MIDI_SLEEP + mSynthLatency) * 0.001)) {
+             time + ((MIDI_SLEEP + mSynthLatency) * 0.001)) {
       OutputEvent();
       GetNextEvent();
    }

src/AudioIO.h

@@ -437,6 +437,11 @@ private:
 #ifdef EXPERIMENTAL_MIDI_OUT
    void PrepareMidiIterator(bool send = true, double offset = 0);
    bool StartPortMidiStream();
+
+   // Compute nondecreasing time stamps, accounting for pauses, but not the
+   // synth latency.
+   double UncorrectedMidiEventTime();
+
    void OutputEvent();
    void FillMidiBuffers();
    void GetNextEvent();
@@ -542,7 +547,9 @@ private:
    /// How many frames of zeros were output due to pauses?
    volatile long    mNumPauseFrames;
    /// total of backward jumps
-   volatile double  mMidiLoopOffset;
+   volatile int     mMidiLoopPasses;
+   inline double MidiLoopOffset() { return mMidiLoopPasses * (mT1 - mT0); }
+
    volatile long    mAudioFramesPerBuffer;
    /// Used by Midi process to record that pause has begun,
    /// so that AllNotesOff() is only delivered once
@@ -613,12 +620,17 @@ private:
    double              mT1;
    /// Current time position during playback, in seconds.  Between mT0 and mT1.
    double              mTime;
-   /// Current time after warping, starting at zero (unlike mTime).
+
-   /// Length in real seconds between mT0 and mTime.
+   /// Accumulated real time (not track position), starting at zero (unlike
+   ///  mTime), and wrapping back to zero each time around looping play.
+   /// Thus, it is the length in real seconds between mT0 and mTime.
    double              mWarpedTime;
-   /// Total length after warping via a time track.
+
+   /// Real length to be played (if looping, for each pass) after warping via a
+   /// time track, computed just once when starting the stream.
    /// Length in real seconds between mT0 and mT1.  Always positive.
    double              mWarpedLength;
+
    double              mSeek;
    double              mPlaybackRingBufferSecs;
    double              mCaptureRingBufferSecs;