Finding out a audios BPM (Beats Per Minute) using PlaybackLoudness?

i_Zolox · April 22, 2020, 2:07am

I know there has been some discussion about a “beat-detection system” in the past. However, the person behind that post was looking to find the High and Low frequencies in the audio.

I am aware that a audios PBL or PlaybackLoudness is a static value with no relation to the audios frequencies, That being said I still want to make a system that will find the average “Beat” or Loudness to determine what tempo, beat, delay I should set on lights to act as if it were pulsating at the beat of the current track. Something similar to how this game does theirs:

EmeraldLimes · April 22, 2020, 5:30am

Not sure what you mean, but I’ve been developing this game, and perhaps this is what you mean by

?

chasedig1 · April 22, 2020, 5:40am

My game does this, it changes the size of the part. Basically, what I do is I change the size of the part on the bottom based on PlaybackLoudness divided by 5, and add that to the original size. You could change the divisor to what works better for your part, but for mine, it’s great.

If you would like to see the game, it is here: Tower Trek - Roblox

i_Zolox · April 22, 2020, 7:22am

I don’t want to change the size or light brightness directly yo the raw PBL as this would be vary aggressive and inaccurate to the actual beat per say

Club_Moo · April 22, 2020, 8:24am

That’s an interesting idea. You’d have to sample it on a regular basis, so you’d need to use
RunService:BindToRenderStep() and then mind the deltas. You’ll have to do filtering on the data,
might not need an FFT, if through the filtering you can pick out the beats. Look up Low Pass Filter, etc.

MagikTheWizard · April 22, 2020, 10:21am

Well I did it for the fun of it when my friend was making Audio Visualizers, but basically here’s what I did:

On heartbeat I’d check the PlaybackLoudness, I have a table where I save the value on heartbeat in so I can “Average” it between all the values, that way we can see what the average of “beats” will be and I just render anything that’s higher than that as a “beat”.

(Of course if you want something more advanced then I’d suggest looking more into sound frequencies)
so basically :

local loudnessValues = {}
game:GetService("RunService").Heartbeat:Connect(function()
   local average = 0
   for _,v in ipairs(loudnessValues) do
        average = average + v
   end

   average = average / #loudnessValues
   local isBeat = sound.PlaybackLoudness >= average
   
    --visualizing code basted on isBeat etc.

    loudnessValues[#loudnessValues + 1] = sound.PlaybackLoudness
end)

Probably not the best way to approach this but that’s basically what I did, yes it’s “real time” and if you’d like to see the output then :
Audio Visualizer - Roblox (open devconsole if you’d like to see isbeat or not)