engine.set_bpm(123.45) should affect MIDI timing

[kyungyunlee]

Hi, thanks for the great library!

While trying to confirm that DawDreamer renders MIDI exactly the same as when rendering with Reaper (or any DAW), I found that DawDreamer renders at a slower tempo. Any idea why this is happening?

I am rendering using Addictive keys with a preset I saved.

  engine = daw.RenderEngine(SAMPLE_RATE, BUFFER_SIZE)
  synth = engine.make_plugin_processor("my_synth", vst)
  assert synth.get_name() == "my_synth"

  if ".vst3" in vst:
      assert synth.load_vst3_preset(vst_preset_path)
  else:
      assert synth.load_preset(vst_preset_path)

  assert synth.load_midi(midi_path)

  time.sleep(0.5)

  graph = [
      (synth, []),
  ]
  engine.load_graph(graph)

  engine.render(duration)  
  audio = engine.get_audio()  # Returns array shaped (2, NUM_SAMPLES)

  sf.write(output_wav_path, audio.transpose(), SAMPLE_RATE)

[DBraun]

Taking a slight guess here. The MIDI file contains BPM information at PPQ-rate. Right now load_midi uses this info to place the notes at seconds positions on the timeline. Then engine.set_bpm(90.) or anything else will actually have no effect. I would want to improve this in the future so that you can change the BPM after loading a MIDI file (BPM does affect plugins and PlaybackWarpProcessor). But long story short, my guess is that the BPM of the MIDI file is not what Reaper is set to.

And the unfortunate short term solution is to use some other python library to parse the MIDI notes and feed them to the synth.add_midi_note one at a time with a custom time-scaling.

[kyungyunlee]

@DBraun Oops, I think it's a Reaper thing...Works fine with Logic Pro! Thanks for the quick comment.

I think the changing bpm option would also be quite useful in the future.

[DBraun]

New features in 0.6.6 fix this!