Removing/minimizing digital distortion

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jan
User offline. Last seen 3 years 20 weeks ago. Offline
Joined: 2006-06-06
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Hi,

I was wondering if there is a way to remove or minimize digital distortion from a recording.

The story: 5 years ago we recorded ourselves with a Sony Minidisc recorder on my fathers 50th birthday. I just found the MDs when I cleaned up my flat. Although we and the crowd were absolutely rocking, the microphone and the MD which were recording the event were driven beyond their capabilities. Very much beyond their capabilities I have to admit, because the digital distortion is pretty bad.

I would like to give this recording to my parents, but first I want to clean up the recording as much as possible. Is there any way to get rid of the distortion or to minimize it?

Thank you for your help.

philicorda
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Joined: 2006-05-16
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Don't expect miracles, but you can try...

A Low pass filter.
The Calf multimode filter plugin is good.
Remove as much top end fuzz as possible before it starts to sound too muddy.

Noise reduction/click removal.
Try http://gwc.sourceforge.net/
Even though it's not designed for removing distortion, there are some similarities with removing hiss, crackle and clicks.

High pass filter.
Heavily clipped digital waveforms have sections of hundreds of consecutive samples at exactly the same level. (Where the waveform peaks would be in a normal unclipped recording). If you normalise to -8db or so, then do multiple (50 or so) processes with a 5hz or so high pass filter, these flat peaks begin to round off.
I think this works because the flat sections are at zero hertz. :) It doesn't do all that much.

BenLoftis
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Joined: 2006-03-27
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There is a "declipper" ladspa plugin (swh-plugins package) that may help. I've never tried it.

jan
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Joined: 2006-06-06
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Thanks for all your help! I will try all of your suggestions in the next few days.

With a bit of luck the distortion could get bearable.

Chichi
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Joined: 2009-06-05
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There are many ways used to take away or reduce digital distortion from a recording. 640-460 Not unless you modify the rules of physics. A flexible limiter can only put off a signal from cutting in the first situate. 70-284 Just the once it is abrupt and flat on the top & underneath, yer screwed. You can't un-clip it. You have twisted a composite waveform into a straightforward four-sided figure signal and you no longer have the information in the waveform that would inform you what the signal should be doing if it had not been clipped. 646-653 Thanks.

Danni
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Joined: 2006-07-05
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Audacity has some tools for this... As long as the waveforms are not too far gone... There is the repair tool that can fix an individual clipping (it guesses where the waveform from looking at the audio either side of the clip. This is incredibly time consuming -- there is also a nyquist plugin that automates the process to a certain degree. but has memory issues and will crash if you try to do too much in the one session. Finally I have a working automated version but I have yet to figure out how to commit it to the Audacity guys.