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I'm putting together a scene with music that has a steady beat, and then the tempo increases to the point where the beat is far more rapid.

I'd like to alternate between video clips on every beat. I can do this by slicing up one clip and have it on a higher track than the other, but that becomes tedious with the amount of times it need to be done and how small some clips need to be because of the tempo increase.

Here's an example from around 2:40 here

So my question is, is there any way to accomplish this in a simple fashion? I'm not sure if I can do this in After Effects, but if I can, I'm willing to.

Thanks

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3 Answers 3

I would imagine that the music video you posted used manual edits to achieve that effect. However, there are a few automated beat detection utilities out there which you might like. One After Effects / Premiere plugin specifically dedicated to beat detection and music is Mamoworld's Beat Assistant. I haven't used the plugin (cost ~$40), but it should work with Premiere or After Effects. You can see a video tutorial and overview here.

For other ideas, Premiere Elements (but not Pro) does have a built-in beat detection feature. You could also investigate Trapcode's Sound Keys plugin, which might help you more quickly place markers on beats by hand. If you can make cuts based on loudness of the music (as opposed to beats), you may be able to use the "Convert audio to keyframes" keyframe assistant.

Unfortunately, I'm not sure if beat detection tools will be able to easily / perfectly recognize an accelerando or tempo increase like you describe. You may be stuck doing some manual editing to at least identify the beats. Using Premiere's "Add clips to a sequence automatically" could speed up your workflow when it comes time to assemble the clips in place.

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Here are some more relevant links: Keyframe assistant > convert audio to keyframes: motionscript.com/design-guide/basic-audio.html Sound Keys plugin: redgiant.com/products/all/trapcode-sound-keys –  ZeroFlux Dec 17 '13 at 1:29

An incredibly easy way to cut this "by hand" would be to nest your alternating clips and turn that nested sequence into a multicam sequence by right-clicking the nested sequence and hitting "Multicam > Enable". Then, by going into the Multicam Editor (Open this in your "Windows" or "View" menu), you can press play and hit "1" and "2" on your keyboard to cut between the clips in real time (supports up to 4 clips).

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I have used a number of pro NLE editors and I have not heard of this kind of automation. It might be possible via a script, but that is not my area, I am a nuts and bolts editor.

However, I think that your video will be much better to have it cut by hand instead of letting a program decide where to cut it. Yes, it will be an enormous chore to get your video to checkerboard or cross cut back and forth so many times so quickly, but if you really dig editing here's your chance to shine besides if you plan to master editing, this is an opportunity to accelerate the learning curve.

Also the speed increase, or accelerating the tempo is another step that makes this even more demanding, and really should be thought out carefully and done by hand.

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