How can I adjust the tempo by percentage? about drywetmidi HOT 8 CLOSED

Hi,

First of all, do you need to change speed of playback using Playback class of the library or you need to create new file that is faster or slower than original one?

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Hi,

Create a new file with faster/slower tempo. Well, I don't need to create a file - just require an object in memory.

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Well, you can use this code:

midiFile.GetTrackChunks().First().Events.Insert(0, new SetTempoEvent(SetTempoEvent.DefaultTempo));

foreach (var trackChunk in midiFile.GetTrackChunks())
{
    foreach (var setTempoEvent in trackChunk.Events.OfType<SetTempoEvent>())
    {
        var microsecondsPerQuarterNote = setTempoEvent.MicrosecondsPerQuarterNote;
        setTempoEvent.MicrosecondsPerQuarterNote = (long)Math.Round(microsecondsPerQuarterNote * 0.8);
    }
}

This code changes all Set Tempo events so playback will be 20% faster (0.8 means quarter note will be 20% shorter in terms of microseconds). To decrease speed use multiplication with values greater than 1.0.

Please let me know if it works.

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This works, thank you.

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Hi,

This method doesn't seem to work on the midi file below. It doesn't match the tempo of the audio file produced by Ableton.

I increased tempo from 120 to 150 => setTempoEvent.MicrosecondsPerQuarterNote = (long)Math.Round(microsecondsPerQuarterNote * 0.75f);

The only difference I can see from the other files I tried is that Ableton recognizes this midi file as having a 6/8 time signature.
ravel_miroirs_3.zip

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Hi,

How did you change tempo with Ableton? Just set 150 instead of 120? And then export to wav? Can you attach audio file produced by Ableton?

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Also why you use 0.75? 120 / 150 = 0.8. 0.8 should give you the correct result.

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Ah. You are right. I was dividing in the wrong order. thanks!

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