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Goal: To create a program that will be able to turn off and on lights to music based on events that are triggered from midi notes.

Hello all, I am hoping that this isn't too broad of a question to ask. I am working on a project where I get events from a midi file and turn those events into time. I take a note from the midi file and append it to a list as the time it was placed

Example: https://i.stack.imgur.com/fVLNO.jpg

I take all of those and place them into a list. Don't worry about how I do that as that is not my main goal to discuss. I've just substituted the list with a hard-coded one on my example code.

I now have a list of times that I want lights to either turn on or off, now I just need to set an infinite loop with a timer that starts at 0 seconds (with the start of the song) and when the timer == (the next time in the list) it will print out a line. Here is my code:

import socket
import sys
import random
import time
from pygame import mixer
from mido import MidiFile

masterList = [12.37, 14.37, 15.12, 15.62,16.36, 17.61, 18.11, 19.11, 19.61, 20.35,]
mixer.init()
song = mixer.Sound('song.wav')
startTime = time.time()
endTime = startTime + song.get_length()
print(masterList)
print('Starting song.')
song.play()
print('Playing song, timer:',startTime)
while time.time() <= endTime:
    #print(round(time.clock(),1),masterList[0])
    if round(time.clock(),2) == masterList[0]:
        print(round(time.clock(),2),"<-",masterList[0],"------------------")
        del masterList[0]
    #print('playing...')
    time.sleep(.01)
mixer.quit()

Here is a video of it runing: https://www.youtube.com/watch?v=VW-eNoJH2Wo&feature=youtu.be Ignore the deprecation warnings

It works but sometimes, due to the nature of programming, the time.clock() does not always == the next item in the list. I knew that this would be a problem going in as you can't rely on how long the code takes to execute. Sometimes it takes a few more milliseconds than usual to complete a while loop so then when you call the time.clock() method it != the next time in the list. Then the list does not remove it's first item and then it will never equal that first item.

I tried going by 10 milliseconds (.1) but it doesn't give me the accuracy I need.

Also, it seems clunky, sometimes the events are delayed a few milliseconds and it makes the effect not as pleasing. As you can see from my video the times of the prints aren't lined up completely where they need to be, even though they are perfectly placed on where they need to be in the midi file.

Question: Is there a more elegant way of tackling this? I seem to keep finding ways of patching it to work better and then it always goes back to the nature of programming, where the cpu always is unreliable. I've been trying to think of different ways of doing this but I can't come up with any. Your help would be much appreciated!!

nmendez
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1 Answers1

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Since you're deleting the notes as you play them, have you tried using >= instead of ==?

E.g.,:

while time.time() <= endTime:
    #print(round(time.clock(),1),masterList[0])
    if round(time.clock(),2) >= masterList[0]:
        print(round(time.clock(),2),"<-",masterList[0],"------------------")
        del masterList[0]

That way the note will play as soon as possible after the specified time, and remove it from the queue. Only way to know actual performance is to test it, but at the very least it won't skip notes.

Kal Zekdor
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  • Oh my... Why didn't I think of this.... Thank you so much! I will incorporate this but again, I am hopfully going to find a more elegant way of doing this. I mean, how to those machines that run light shows to music work? There has to be a better way – nmendez Dec 15 '18 at 05:15
  • You may want to look into https://www.pygame.org/docs/ref/event.html since you're using PyGame, but sometimes the simplest answers escape us. Edit: Assuming you can process the song file in realtime, if you're doing pre-processing your approach isn't a bad one. – Kal Zekdor Dec 15 '18 at 05:20