Enhancement: Removing swoosh noises

[Steve Crook]

I've got a number of LPs where one channel has repeating swoosh noises, each swoosh lasting no more than one second. When I look at the waveform in the cleanup view at 2-5000% I can see tiny spikes in the basic waveform, at lower zoom levels the wave just looks fatter than you'd expect.

They're impossible to remove by using normal click removal, but can be cleaned by doing manual repairs. At the default repair width a single manual repair follows the basic waveform really well and eliminates these tiny spikes quite effectively.

But even to remove a relatively short stretch needs a lot of manual repairs.

Would it be possible to select a region in the waveform and then have VS automatically apply a series of manual repairs to fill the selected region?

In the attached screenshot the waveform is 5000% and the highlighted repair is ~170 samples at 192kHz. I hope this explains what I'm trying to achieve...

[Paul Sanders (AlpineSoft)]

I'm not sure I understand this.  Do you mean that you want a single repair covering the entire region, or something else?  I don't understand what 'a series of repairs' might look like.

[Steve Crook]

> Do you mean that you want a single repair covering the entire region, or something else?

1. I select a region in the recording, say 1sec.
2. I ask VS to make a series of contiguous small repairs to that region

My experiments show that a series of relatively small repair regions fit the overall shape of the waveform really well, don't significantly clip peaks, or otherwise mess with the recording. But they do remove those very small peaks that make up this sort of noise. The wider the repair the poorer the fit to the waveform hence wanting a series of contiguous small repairs.

But, obviously, even for a single second, this could be a lot of repairs. At 10 samples per repair @ 192kHz it's ~18k repairs and I can see this would be disruptive for the VS UI as it stands and would pretty much destroy the corrections list. I guess it means inventing a completely new class of repair...

I think what I'm asking for is the equivalent of very fine sandpaper. The sort we use to smooth a rough surface but without changing its shape in any way. I'm sure there are curve fitting algorithms that do this to remove sample noise, but it's not my field.

If I've still not explained myself properly, I apologise. I could provide an album where I've made a short section of these repairs by hand...

[Paul Sanders (AlpineSoft)]

OK, I think I understand now.  Do the repairs really need to be that narrow?  We have optimised VinylStudio to handle a large number of click repairs and something like 100k repairs total (probably more) works fine, but I can see that you might greatly exceed this with this approach if you want such tiny repairs.

[Steve Crook]

Smaller repairs give a better curve fit though the 10 sample width was an extreme I'm regretting suggesting. I'm not saying this is how it should be done, but the only way I could manage it with VS as it is at present.

The original screen print showed a repair of 170 samples but a repair of this width doesn't always leave the overall waveform intact on peakier sections. Perhaps up to 100 samples? If you're interested I can experiment with a few recordings and see what gets the job done with the least damage.

Everything that needs to be removed is generally very low level. Sometimes barely more than small bumps. See the attached image. This is at 5000% and significantly horizontally zoomed. You can see the unevenness in the waveform. It's audible as background noise, largely invisible on speakers unless the music level is low, but inescapable on headphones.

The higher level noise is still way below anything click repair would pick up.

[Paul Sanders (AlpineSoft)]

Hi Steve,

Yes, I'm interested, provided that I can implement it as a series of regular click repairs.  We could call it 'smooth waveform' or something.

100 samples is certainly more reasonable than 10, but it's still uncomfortably small.  So yes, do please experiment and make me an offer.  Also, how long are these swooshy bits (in terms of time) and how many are there please, on a representative recording?

[Steve Crook]

This is a section of a track with this sort of noise. Overall it lasted around 8 seconds, basically on one channel. The image is at 5000% vertically zoomed. It's probably at the worst case end of things mostly the sections of noise are shorter than this, though I've got a few LPs with lower level noise that extends across a whole side.

[Paul Sanders (AlpineSoft)]

OK, thanks.  How many repairs did you need put in and what repair width did you go for in the end?  Also, how long did it take you!

I'm in the throes of cleaning up some old and hairy code at the moment, but once that's done I'd appreciate a copy of that recording (and perhaps one or two other similar ones).  I do like the idea of adding this feature, if its feasible to do so without major surgery.