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Forum: General Discussion

Topic: Tempo Detction Algorithm
Can someone explain how the tempo detection algorithm works.

I had it analyze one of the tracks I used when I was a beta tester for Presonus Studio One.
FYI, I was a beta tester from 2010 to 2025. When Fender changed the name to Studio Pro all beta testers contracts were termed.
VirtualDJ failed the tempo analysis for my track in the first 28 seconds. The tempo algorithm was set to FLUID. The algorithm then corrected itself and locked in to the tempo for the rest of my track. What I'm seeing in the waveform is that the algorithm is not 100% detecting the transients due to the variance in where the VirtualDJ places its measure / beat markers.

Does the algorithm analyze from the start of the file or does it start analysis at the first transient?

My track has a variable tempo around 107 BPM.
 
Posted 2 days ago @ 3:57 am
Without knowing what the track is, or seeing a pic of the analysis in the BPM Editor it's hard to comment.

What's the track (artist and title)? Is it commercially available?

What genre is it? Does it have a regular 4/4 time signature all the way through? Are there any sections where the drums/perc are not present?

VDJ will analyse the whole thing, but it does rely on there being a discernable pulse, so ambient sections can cause problems. It's possible to edit and correct in most cases.
 
It’s actually a variable tempo quarter note click track utilizing a sidestick for sound
 
OK so not something you'd typically be playing out to the audience or beat mixing with another track. 😍

Shouldn't be too difficult to edit the grid into place though, if it's only a click. You said it "failed" but how badly out was it?

Yes ideally the algo should be able to follow a simple regular pulse, but it's probably tuned more to kicks....
 
 
It's just a click track, not something with an artist and title.
 
Saw the context after the post. Will leave regardless, in csse he wants to try general songs too.
 
Being a retired musician who started playing with click tracks in 1987, I like to evaluate how a beat detection algorithm detects tempo using a click track. One can see how the algorithm actually analyzes transients. Plus, from my years of experience beta testing with Presonus Studio One, the click tracks give the algorithms the most difficulty.
 
groovindj wrote :
You said it "failed" but how badly out was it?
 
groovindj wrote :
You said it "failed" but how badly out was it?



In the first maybe 12-16 measures, the algorithm at times were almost an 1/8th note off. This was the section that had the extreme variable tempo. Then the algorithm started to stabilize.

FYI, the click track is for one of my backing tracks of a popular pop song. I’m also going to analyze the commercially released version and compare.
 
byronsanto wrote :
the extreme variable tempo

In the 1st post you said it was around 107. Now it has extreme variations? ☹️

byronsanto wrote :
a popular pop song

Is there any reason you're not stating the artist and title (as requested earlier)?

Then we can all take a look - including the devs. 👍
 
Tempos can have an average even though the variable tempo can be outside of the average range for a period of time.

The click track is from a backing track for 24K Magic. I created the backing track maybe 95% to the original in regard to tempo.

Then one must consider the sound used in the click track in which VirtualDJ is analyzing. The initial transient may be confusing the analysis.
 
Thanks for the info.

24K Magic by Bruno Mars is a modern track with a rigid tempo. It's exactly 107 all the way through, from where the beat kicks in at 23 seconds.

The talkbox intro was probably done completely free style, but seems to be in the low 90s.

[EDIT] According to the guy who recorded it (Mr Talkbox) Bruno sent him the intro and he'd not heard the rest of the song. link to video

Actually if started in the right place (so the 'night' of 'tonight' falls on the one), the beat kicks in on tempo at 107.

....but yes, the algorithm struggles when it can't find a clear tempo.



From a DJ point of view, if mixing into 24K Magic, we'd skip the intro and blend in at 107. If coming out of a slow jam set, it could be played including the intro.