Can this audio be corrected?

[adom]

Hello,
not so long ago I made some LIVE recording in my city and after I got home I noticed that sound was not good - most likely it was too loud during recording so now it sounds bad (I don't know english word for this).

Can this be fixed somehow with some special filters?

Thanks.

[pandy]

This English word is clipping and such distortion can't be fixed - you can try to partially reduce perceived clipping - there are some filters or plugins that may help, Adobe Audition is equipped with some filter capable to improve - partially restore clipped audio however this is not magic - by introducing clipping you loosing data and introduce some harmonics not present in signal - filters may do some blind guess how reshape clipped audio to extrapolate such lost information but it is never same signal as it should be.

https://en.wikipedia.org/wiki/Clipping_%28signal_processing%29

[adom]

Thank you for that short explanation and that link - now i know what is going on.

[manono]

The ReLife VST plugin is pretty decent at fixing clipping. I use it in Audacity but I believe most WAV Editors can use VST plugins. I'll enclose it as I'm having trouble finding the latest version (1.42) before it went to payware with a demo. Scroll down for information about the included Ver. 1.42:

http://www.terrywest.nl/utils.html

[pandy]

This is very nasty clipping as low frequency are heavily clipped however seems that medium and higher frequencies are less affected - there is problem with harmonics from clipped bass line - perhaps doing manual equalization to remove fundamental bass line with harmonically related frequencies can cure this recording but not sure if this is guarantee for success... series of notch filters perhaps with some form of low frequency envelope tracking may work...

[JVRaines]

I don't think the clip filters will work because this is analog distortion, not digital clipping. It could even be what the concert loudspeakers were reproducing. Do you remember how they sounded in person?

[adom]

I have downloaded and installed that filter - will play with it this afternoon and see if I can get any promising results.

... It could even be what the concert loudspeakers were reproducing. Do you remember how they sounded in person?

Hmm... don't remember (I was so absorbed in recording that didn't notice) but you could be right about that because one day earlier I was recording another concert from very same spot and the sound was recorded without any distortions.

Anyway I will try that filter manono pointed to but I know now there may be no improvement at all.

[davexnet]

I had a try using one of the other Demo VST plugins you can find on the interweb, it's called "Perfect DeClipper".
I converted the file to two channel WAV first. The Plugin seems to have removed a little of the fuzziness,
but whether the result is an improvement on the source is debatable.

[adom]

I think there is a slight improvement over the original - I got similar results with Audacity and ReLife plugin - looks like pandy and JVRaines were right: there's not much that could be done.

Anyway, thank you guys for explanation and showing your interest.

[-Habanero-]

This is not a clipping problem, the problem is periodic silencing of the audio. There are tiny, frequent gaps all over the place. Good luck fixing that. The gaps can be interpolated but I don't know of any filter to do this automatically or how good the replication would be even if it could.

[JVRaines]

I'm looking at the waveform in Adobe Audition and I can't seem to find those tiny, frequent gaps. Where are they?

[-Habanero-]

Use a spectrograph instead of a waveform. The most obvious is from 8.000 - 8.300 seconds. But even in the waveform you can see inaudible gaps. Notice there's no content above like 10 Hz in them? The rumbling from the big speakers at the concert was interfering with the inadequate equipment.

If there was clipping, it would look like the second pic which I gained by 15 dB and then brought it back down.

EDIT: Here's also the spectrographic view of the gaps.
http://s14.postimg.org/d2w19po1d/spectrogap.png

[aedipuss]

it may have been the sound pressure level overloading the mic capsule in the recording device causing it to cut out each time. you can see the dropouts in a spectrogragh.