Is there a tool for fixing-up clipped audio?

peterh337 wrote on 6/20/2017, 2:06 PM

I have heard of such tools - they are mentioned here and there online - but there seems to be nothing in Sound Forge Audio Studio that I have.

I also have a collection of old sound editors going back about 20 years but I don't think any of them has anything either.

I am an electronics design engineer so I know that once you saturate and clip the information is gone for ever, but one could much reduce the very bad distortion by detecting the clipping and rounding it off appropriately.

Comments

rraud wrote on 6/20/2017, 3:46 PM

Sure, a lot of waveform restoration tools are available. Magix NR-2 suite (included w/ Sound Forge Pro) has the 'Clipped Peak Restore' plug in. SFP also includes some iZotope plug-ins that can be used. All work very well for occasional digital 'overs'. However.. a severely clipped waveform and analog (preamp) distortion are not so easily fixed, and many cases, just plain can't be repaired, at least not w/o generating other awful sounding artifacts. Magix's SpectralLayers or iZotope's RX can be considered, but are costly and have a steep learning curve. Even with the best of the best, some types of distortion can't be repaired.

peterh337 wrote on 6/20/2017, 3:56 PM

Hmmm... I have Vegas Pro 14 (the $250 upgrade from 13) but have only the Sound Forge Audio Studio 10.

I also have the ancient Cool Edit 2000 :)

This is for very rare situations and I don't really want to spend hundreds on it...

Dexcon wrote on 6/20/2017, 6:58 PM

The free sound editor, Audacity, has a "Clip Fix" function under the Effects tab. I have not used it so I cannot attest to its effectiveness, but at least it is a free option for you to try out.

peterh337 wrote on 6/21/2017, 12:52 AM

I have just tried Audacity's Clip Fix and it works.

It took a while to work it out though. First you have to convert the audio to floating point. Then you have to reduce amplification by -10 dB (using Effect > Amplify) to create headroom for the new (interpolated) peaks.

Also the clip fix doesn't work on audio beyond a certain length. I didn't test it but it looks like more than half an hour stops it working. It completes ok but has not changed anything. So one has to process say a 2hr file in multiple pieces.

Dexcon wrote on 6/21/2017, 1:30 AM

Given the height of the waveform in the attachment, just checking that you first followed Audacity's recommendation for Clip Fix in their user manual:

Before use, reduce amplification by -10 dB using Effect > Amplify... to provide headroom for the reconstruction.

peterh337 wrote on 6/21/2017, 2:29 AM

Yes; I edited my post after you read it :)