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Pitch changing software to remove speed variations.

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Pitch changing software to remove speed variations.

Postby James Perrett » Sun Nov 18, 2018 9:44 pm

I'm currently involved in a project where one of the recordings has quite a few pitch variations. It sounds like the tape was catching on the edge of the reel or on some leader tape which caused it to slow down slightly at intervals.

I can see the pitch variations if I look at a spectral view but my problem is that they are too complex to be handled by the tools in RX Standard or the version Adobe Audition that I have. These require you to draw a pitch envelope in a separate plug-in window and, as these variations require at least half a dozen points to be drawn each time, it is almost impossible to line up the points on the curve with the variations shown on the spectral display.

Now I know that Celemony's Capstan is intended to be used for this sort of problem but this project doesn't have the budget for that. I also found something called Pyrespeed but it comes as Python source code and seems to have all kinds of external dependencies which make it difficult for the average user to even contemplate trying it. Another blog mentioned software developed for Matlab but didn't say whether it was available for others to use.

I'm wondering whether I might be able to use Reaper's spectral display but the speed control envelope is only available on the master track and I don't think that you can create a spectral display on the master track.

So I was wondering whether anyone knows of some software that will allow you to create a speed/pitch envelope over a spectral display of the audio? Even better would be software that will show the results of the speed/pitch modifications on the spectrum - does this exist?

Of course the other issue is that it needs to be inexpensive as this isn't something I often need as I've usually managed most things with Audition/Reaper in the past.
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Re: Pitch changing software to remove speed variations.

Postby Matt Houghton » Sun Nov 18, 2018 11:04 pm

Could you use Reaper's stretch markers and disable the pitch preservation? I'm pretty sure that works in a similar way processing-wise to the master tape-speed effect, even if a touch more fiddly.
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Re: Pitch changing software to remove speed variations.

Postby Tim Gillett » Mon Nov 19, 2018 2:32 am

James, is this a music or speech recording? Capstan only works on the polyphony in a music recording. Unless there is some other embedded speed reference like a mains hum or harmonic, I assume any other tool would have to utilise the same Capstan polyphony principle on musical content. Any chance of a short sample of a few speed deviation instances?
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Re: Pitch changing software to remove speed variations.

Postby desmond » Mon Nov 19, 2018 2:57 am

James Perrett wrote:I can see the pitch variations if I look at a spectral view but my problem is that they are too complex to be handled by the tools in RX Standard or the version Adobe Audition that I have. These require you to draw a pitch envelope in a separate plug-in window and, as these variations require at least half a dozen points to be drawn each time, it is almost impossible to line up the points on the curve with the variations shown on the spectral display.

There could definitely be an improvement in RX's toolset for this - I don't think it automatically analyses the audio and shows the pitch curve (like Capstan does), it just lets you manually create a pitch curve to apply to the audio. Should be a feature request to iZotope I think...

Note - you can resize the plugin window to be as large as you need, should you need more space to work in.
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Re: Pitch changing software to remove speed variations.

Postby James Perrett » Mon Nov 19, 2018 2:43 pm

Many thanks for the replies...

I hadn't thought of using stretch markers Matt - in fact I didn't realise that there was an option to use them to change speed as I've only ever used them to correct timing while keeping the pitch constant.

Tim - this is a music recording and these variations often happen where there are long notes so they are easy to see. I'll see if I can post a short sample...

Desmond - I was actually using the RX editor and couldn't find a way to resize the tool window but maybe I should look again (I don't know if the Mac is different in this respect). It would certainly help if I could match the selection size with the tool window size and maybe use RX's transparency feature to overlay them. The other problem with RX is that I can't find a way to zoom in on the vertical scale in the tool window - currently it is set to +/- 20 semitones which is far too much for what I need and makes fine adjustments difficult.
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Re: Pitch changing software to remove speed variations.

Postby desmond » Mon Nov 19, 2018 3:15 pm

James Perrett wrote:Desmond - I was actually using the RX editor and couldn't find a way to resize the tool window but maybe I should look again (I don't know if the Mac is different in this respect).

On the Mac at least you can just drag the lower right corner and resize just like any other window.
it even says this in the RX7 manual in the Variable Pitch chapter:
"Click and drag on the bottom right-hand corner of the module window to customize the window size."

James Perrett wrote:The other problem with RX is that I can't find a way to zoom in on the vertical scale in the tool window - currently it is set to +/- 20 semitones which is far too much for what I need and makes fine adjustments difficult.

I couldn't find a way to change this either (can only shift it, or reset it, but not change the pitch range - the manual implies it's always a fixed range) but at least if the window is larger it's a bit easier to work with. Would be worth playing with at least to see whether it's a viable approach...
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Re: Pitch changing software to remove speed variations.

Postby The Elf » Mon Nov 19, 2018 4:46 pm

I've done this kind of thing in Cubase's VariAudio. I know that doesn't help directly, but to just to let you know it's possible.
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Re: Pitch changing software to remove speed variations.

Postby job » Mon Nov 19, 2018 6:22 pm

James Perrett wrote:...a way to zoom in on the vertical scale in the tool window - currently it is set to +/- 20 semitones which is far too much for what I need and makes fine adjustments difficult.

Put your cursor over it and scroll with the mouse wheel/track pad to zoom the semi-tone scale.
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Re: Pitch changing software to remove speed variations.

Postby desmond » Mon Nov 19, 2018 6:27 pm

job wrote:Put your cursor over it and scroll with the mouse wheel/track pad to zoom the semi-tone scale.

Nice, works for me! I tried every combination of mouse+modifier I could think of, but didn't try that... thanks! :thumbup:
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Re: Pitch changing software to remove speed variations.

Postby James Perrett » Mon Nov 19, 2018 7:48 pm

Looks like this is an area that has been improved in RX7. I've just tried the demo and found that the pitch module is much closer to what I was looking for as you can now see the spectral view in the variable pitch window. I can resize the window but still can't zoom in on the vertical axis as I don't have a scroll wheel on this laptop.

Hmm - I missed the recent RX upgrade window but I'm hoping that they'll do what they usually do and give me an even better offer in a few months.
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Re: Pitch changing software to remove speed variations.

Postby desmond » Mon Nov 19, 2018 7:56 pm

On the Mac, a two-finger scroll gesture also zooms the vertical axis. Maybe you have some similar trackpad gestures on Windows..?
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Re: Pitch changing software to remove speed variations.

Postby James Perrett » Mon Nov 19, 2018 8:56 pm

desmond wrote:On the Mac, a two-finger scroll gesture also zooms the vertical axis. Maybe you have some similar trackpad gestures on Windows..?

Thanks Desmond - that vertical zoom works in exactly the same way on Windows in both RX6 and 7. By some judicious use of zooming and transparency I can overlay the window too.
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