Distortion Caused by Too Much Mic Gain - Can This Be Removed

[brianejsmith]

I made a recordng but had the Mic Gain up too high. When the volume produced by the singers exceeded a certain level distortion was added by the recorder.

Is there any way this can be removed?

[DVDdoug]

There is a Declipper tool ("effect") that you can try. (I'm not sure where I got it... It might be one of the LADSPA Plug-Ins.)

There are other de-clipping and clip repair tools too, but none of them are perfect. Clipping (distortion) happens when you hit a limit and the top (and bottom) wave peaks become flat-topped. In this case you clipped your analog-to-digital converter during recording. The problem is, information is permanently lost and there is simply no way to know the shape or height of the original waveform.

[brianejsmith]

Really kind. Thanks for the info; and the explanation which will help me next time.

On the hunt now for a declipper. There isn't one in my Audacity 2.0.2 set-up that I can see.

[steve]

Audacity has an effect called "Clip Fix" which is below the dividing line in the Effects menu. It's as good as most other clip repair tools but the general rule is that if the clipping is severe enough to hear, then it's probably too severe to repair effectively.

[brianejsmith]

Audacity can "see" the clipping but if I use clipfix it either removes so much that the soundtrack is affected or not enough so that the clipping remains.

I suppose removing a "clip" removed whatever was recorded at the same instant?

It can't reinstate because it doesn't/can't know what to put back?

[steve]

It can't reinstate because it doesn't/can't know what to put back?

That's exactly it.
ClipFix detects where the waveform has been cut off and attempts to reconstruct the missing part by extrapolating the waveform from just before to just after the "missing" part. It is "guessing" what the waveform might have been like before it was clipped. If the clipping is only very minor, then it can guess quite well and do a good job. The more that is missing the harder it is for ClipFix to guess and the less effective the repair is.

[Djard]

You might try zooming in to the most conspicuous spikes of distortion and either lowering their volume with the "Amplify" tool; or, if they appear briefly, cut them out and extend the truncated note by cutting and pasting the signal immediately before or after the cut part. If the edit causes "pop" artifact, try to perform the edit on, say, a drum beat to mask the artifact. The latter option is labor intensive and time-consuming. The best solution would be to re-record the track if possible. Some editing artifact can be ameliorated by attenuating the frequency with the equalizer.

[kozikowski]

See number two.

-- The Four Horsemen of Audio Recording (reliable, time-tested ways to kill your show)
-- 1. Echoes and room reverberation (Don't record the show in your mom's kitchen.)
-- 2. Overload and Clipping (Sound that's too loud is permanently trashed.)
-- 3. Compression Damage (Never do production in MP3.)
-- 4. Background Sound (Don't leave the TV on in the next room.)

The Clip Fix tools actually do a credible job assuming the damage is not too severe, but gentle distortion is never a reason to post on a forum. Posting happens when your show is already trashed.

[steve]

The latter option is labor intensive and time-consuming. The best solution would be to re-record the track if possible. Some editing artifact can be ameliorated by attenuating the frequency with the equalizer.

Yes there are things that you can do if it's a once in a lifetime recording and you have infinite patience, including "drawing in" the waveform with the Draw tool, then smoothing it out with the Repair tool, but unless you have the original Watergate tapes it's probably not worth the effort....."Ameliorated", what a lovely word

[brianejsmith]

Basic problem is you can't record/film and perform at the same time. I need a better monkey!

All in all, the video recorder only cost £159 so I can't ask for too much. But learning enormously as I go here. Thanks to everyone for their help and contributions.

PS "Some editing artifact can be ameliorated by attenuating the frequency with the equalizer" is a rather beautiful sentence; especially for a "techie" oriented person. I particularly like the use of "artifact" rather than the more tempting "artifacts". Delightful use of English.