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Fix get_piano_roll pedal implementation #195

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Fix get_piano_roll pedal implementation #195

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42bd646
Fix get_piano_roll rounding error with pedal
TimFelixBeyer Nov 6, 2020
8e96587
Off-by-one
TimFelixBeyer Nov 6, 2020
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19 changes: 16 additions & 3 deletions pretty_midi/instrument.py
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Original file line number Diff line number Diff line change
Expand Up @@ -118,29 +118,42 @@ def get_piano_roll(self, fs=100, times=None,
for note in self.notes:
# Should interpolate
piano_roll[note.pitch,
int(note.start*fs):int(note.end*fs)] += note.velocity
int(note.start*fs):int(note.end*fs)+1] += note.velocity

# Process sustain pedals
if pedal_threshold is not None:
CC_SUSTAIN_PEDAL = 64
time_pedal_on = 0
time_pedal_on_exact = 0
is_pedal_on = False
# Keep track of non-quantized offset times
end_times = np.zeros((128, int(fs * end_time)))
for note in self.notes:
end_times[note.pitch, int(note.start*fs):int(note.end*fs)+1] = note.end

for cc in [_e for _e in self.control_changes
if _e.number == CC_SUSTAIN_PEDAL]:
time_now = int(cc.time*fs)
is_current_pedal_on = (cc.value >= pedal_threshold)
if not is_pedal_on and is_current_pedal_on:
time_pedal_on = time_now
time_pedal_on_exact = cc.time
is_pedal_on = True
elif is_pedal_on and not is_current_pedal_on:
# For each pitch, a sustain pedal "retains"
# the maximum velocity up to now due to
# logarithmic nature of human loudness perception
subpr = piano_roll[:, time_pedal_on:time_now]

# Rounding might cause notes to be held for longer
# than would be correct, so we have to take the
# exact timing into account
held_notes = end_times[:, time_pedal_on] >= time_pedal_on_exact
piano_roll[:, time_pedal_on] *= held_notes
subpr = piano_roll[:, time_pedal_on:time_now+1]

# Take the running maximum
pedaled = np.maximum.accumulate(subpr, axis=1)
piano_roll[:, time_pedal_on:time_now] = pedaled
piano_roll[:, time_pedal_on:time_now+1] = pedaled
is_pedal_on = False

# Process pitch changes
Expand Down