How to clean a digitally-distorted recording?

Question

We all know what happens when the recording level goes too high during Analog to Digital conversion: harsh non-musical sound covering everything else (ok, on occasion it might be sort of musical, but that's not the point here). It may also happen for no apparent reason with a buggy soundcard (my case here).

I assume that a totally distorded material will be unrecoverable, but most of the time, only peaks here and there will be affected.

So, do you know any tools that might be of help to erase or soften the digital distortion?

Answer 1

iZotope's RX software is an excellent suite of Noise Reduction tools. They all work really rather well. However, two of them stand out for me as for background noise over dialogue it doesn't compete with the likes of Cedar.

DeClipper - it is able to extrapolate a clipped waveform, therefore removing distortion from a recording. It is quite amazing and does a great job. Now, it doesn't work 100% of the time, especially if the entire recording is distorted. e.g. bust stylus on a record player.

My other favourite is the Spectral Analyzer. Being able to see a graph that displays time and frequency has been a real eye opener and I've been able to use takes that would otherwise sound awful and turn them into perfectly usable ones.

http://izotope.com/products/audio/rx

There's a demo available and the basic version costs $350.

Hope this helps and good luck.

Ian

Answer 2

Cool Edit/Adobe Audition has a Clip Restoration tool.

Answer 3

I have a lot of luck with the Sony Oxford Declicker, especially for dialogue - really softens up the harshness of the distortion, if not removing it completely...

Answer 4

Also +1 for iZotope's RX. I just had to use in a mix archive footage of terrible quality. It was very noisy and mostly clipped. I used both the denoiser and and the declipper and achieved some good results.

Answer 5

Try the Waves Restoration tools. X-Click and X-Crackle are your friend for repairing transient distortion and digital (or analog) clicks and static. I believe there is a demo available.

If you have longer bits of distortion, however, you may be out of luck as no software package will be able to extrapolate entire passages of audio from the surrounding regions.

Answer 6

Waves De-crackle does an OK job of helping to repair clipped audio but the iZotope RX is brilliant. It has saved many of my clients lives. I did a series of shootouts and reviews in Sound on Sound a while back.

http://www.soundonsound.com/sos/aug05/articles/ptrestoration.htm

http://www.soundonsound.com/sos/nov07/articles/restoration2.htm

http://www.soundonsound.com/sos/jul08/articles/izotoperx.htm

Hope that helps,

Mike.

Answer 7

I usually use iZotope's RX and Waves Restoration Tools. In some cases I found useful the Uncompressor of the Waves C4, combined with some phase inversion triks.