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Correct distorted audio due to hot levels.
Any suggestions as to which audio filters should be used to correct or improve distorted audio. the levels were recored hot.
Toss High and Stay in Step
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9 Replies
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If they were clipped in digital recording there’s really nothing you can do.
If it was distorted on analog tape you may be able tp reduce the effect with careful EQ slotting out the frequencies that make the room wobble. But you can’t bring it back, it’s still going to sound like it was… distorted.
If there’s only an ioccasional analog distortion you may also want to try dipping the level at those exact points.
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Thanks!!
Toss High and Stay in Step
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you could try compressing it with a good tube plug in pro tools to smooth it out.
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Minor improvment can be made with the CEDAR decrackle module in the CEDAR for WIndows software. It won’t cure the problem but it does soften a bit.
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no – a compressor will not improve an already distorted signal. If the compressor was in the recording chain, it would be used to keep the rogue transients in check and give a smoother overall level, but adding one after the fact is a wholly pointless exercise…sorry!
One thing you could try in ProTools ( and be very careful when trying it) is to use the pen tool to round off the clipped waveforms…bear in mind that this is only worth attempting on very small occasional distortions – there would simply be too much to do on a large clip. And be judicious because it can easily do more damage. Sometimes the best option is to re-record the offending bits.
adam
Editor/Mixer
Character Options Ltd
Oldham, UK -
I have just tried using Sourceforge Audacity to do this and I can report reasonable success.
I have seen someone working on ProTools round off clipped waveforms with the pen tool but I didn’t want to have to buy ProTools just to do that.
Audacity is a free download from:
https://audacity.sourceforge.net/download/
I did risk the Beta version and had no problems.
You need to export the sections of audio that need fixing as precisely as you can. Open it up in Audacity and then magnify the waveform until you see the sample nodes (dots on the waveform).
Be warned now that there are 1000 samples (or dots) per second.
When you scan through the waveform it appears that crackly distortion shows up as visible irregularities in the wave form.
Whilst it is possible to use the pen tool to manually adjust each node individually, I found it slighty quicker to (using the selection tool) select the irregularity (hump or spike) with a few samples either side and then apply the “repair” effect which will instantly, and very satisfyingly, iron out the irregularity before your eyes.
If you are used to Soundtrack Pro you will find Audacity clunky and awkward to use. I spent a lot of time trying to find the playhead on the timeline.
Some of that may be ignorance on my part and some of it may be down to Audacity being a free 7mb downloadable app.
It took me about an hour to go through 2 seconds worth of faulty audio. This may be because I was just getting the hang of it but at best it is pretty laborious.
But if you are stuck it does iron away the crackly distortion and gives you passable audio where before it was totally unacceptable.
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OK – I can now revise the previous time of 1 hour to go through 2 seconds DOWN to 3-5 minutes to process 1 second.
Before I had magnified the timeline right down so the nodes were spaced about 4mm apart visually.
This time I stopped at the first magnification increment that gave me the nodes. This enable me to whizz through and apply the repair filter much more quickly.
I forgot to mention also that the repair filter will only allow selection and repair of up to 125 samples at a time.
But hey – now we’re cooking!
First post prod color correction, then “smoothcam” – now this. Soon you won’t need any acquisition skills or discipline at all!!
Woo Hoo!
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Thanks, that’s a great tip! It really works…doesn’t take long. It’s just a matter of getting it to look like mountains, and when the mountains and valleys are flat because they went over the edge, just apply “Repair.” Works even better with a negative amplify so they don’t go to the edge. It’s nice to know too that sometimes one might be able to get the data from one channel that isn’t distorted, but just the Repair tool in that Beta-Audacity works great.
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I have been attempting to use the Audacity app to clean up some distorted audio. I have about 7 seconds to clean, but I checked after “Repairing” the first two seconds. Now it sounds as though the VO was recorded under water. I followed all the directions posted but it does not seem to be working. Am I doing something wrong?
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