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Is there an automatic way to warp one audio track to another (same performed music)?


bhuether

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Hi,

 

I am about to make some guitar music videos. I am recording audio in a separate room, from where I am doing the video. I am doing solo performances, so it is just guitar. This means I will have two audio files that are similar. Since it is solo performances, I speed up, slow down a bit between recordings. So what I need to do is warp my separately recorded audio to the video's audio.

 

Is there a way to do this automatically? This does not amount to simply shifting one audio track by some constant time. It amounts to adjusting one file to match the contour of the video's audio, which amounts to time warping (while preserving pitch).

 

I can do this manually, but I am hoping there is automatic method, and since the two audio files are of same performed music, I figure there has to be some cross-correlation based method that can automatically stretch one audio file in an adaptive way such that the result is an audio file that is almost totally in sync with the video's audio.

 

Ideas?

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This will be either tedious or expensive or both.

 

Instead, record the video with camera audio, the re-record audio with the video-sound in your headphones. This ensures sync without effort. Or you do it the other way round and mime to the recording.

 

Beware the youtube-fake-guitar-police though, they're ruthless.

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When I record the audio that I want to use, I want to focus 100% on the performance. If I am recording while listening to a previously recorded performance, then that is going to distract me quite a bit.

 

This should be doable using a cross correlation approach. The way I picture it working is I choose some number of contiguous segments in the reference audio, which would correspond to, say, bars in the audio from the video. In the desired audio file I play the same solo piece on guitar, which means every bar of music played in the reference audio is also played in the target audio.

 

Then the algorithm iterates through the 100 segments. For a given segment, it then performs cross correlations across sliding windows in my desired audio file. In theory that should result in a pretty strong peak in the correlation where I play the corresponding part in the desired audio file. So that should give me 100 adjust points/markers in the target file and then perform warping of each segment in the target file. so that bars in target are starting/ending at same time as bars in the reference.

 

Maybe Smart Tempo can help here?

 

But, in the end I may just do this manually...

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If I am recording while listening to a previously recorded performance, then that is going to distract me quite a bit.

No offense, but musicians in the studio do this constantly. Also, if you've ever played in a band, you were also playing while listening to the others. Anyway, shoot the video while listening to the recording and the recording will be great.

 

This should be doable using...

And it might. However you have a task to complete (or so I guess), so pipe dreams won't help you.

Also, by twisting and bending your great recording to the video, you're compromising the quality of that recording.

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While it's not possible to do it automatically*, you could do it manually, using Flex Time. If the the tempo differences are subtle and the transients easily identified, then it shouldn't be too difficult, however it will be a time consuming process.

 

Actually you may want to try using Groove Tracks? It depends so much on the type of material recorded, on how easy it is for Logic to detect transients etc... that it's hard to tell if this is going to work or not, but if it works, then Groove Tracks is the automatic way to match your recording's transients to the position of transients on another track.

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The pieces I am playing are classical, on steel string acoustic, flat picked. So there should be good transients. Though, some of them are rather fast tempo, like some Bach stuff, and Paganini, where transients might be blurred more. I guess I will just do the recordings then figure out a method afterwards :-) thanks
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Just learned of a plugin for Reaper that seems to do exactly what I need:

 

https://forum.cockos.com/showthread.php?p=2354401#post2354401

 

I think it is more suited for vocals, but given nature of what I am recording I think it might just be a promising solution. Will check it out, and compare with groove tracks method as well.

 

 

thanks,

Brian

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