Over modulated audio

Former user wrote on 9/6/2010, 12:26 PM
I was given a tape (Mini DV) that has badly over-modulated audio on it (an interview with a clip-on mic). The waveform(s) are clipped at least half the time, and the nature of the person speaking is to really project their voice -- which makes it even worse.

There is very little chance of getting the audio recut. Is there method for trying to recover the audio? It doesn't have to be perfect, but right now it's so distracting that I really can't use it.

Thanks for any suggestions offered.

Jim

Comments

Byron K wrote on 9/6/2010, 12:56 PM
I feel your pain. Coming from the audio side, I've found that distorted audio is much much harder to fix than low levels. ):

Some things I've done to try and get something salvageable is to run it thru a compressor and try to get the levels down nicely then use EQ to bring down the frequencies that are tending to drive the levels out of range. You can also try to raise the frequencies slightly that are not distorting to enhance the voicing. It may not sound "natural" or the same as the the original recording but hopefully get something usable.

If you have good audio software you may be able to shape the clipped wave forms to curve nicely but that is a LOT of work.

Maybe others have some software or better recommendations.
rs170a wrote on 9/6/2010, 1:04 PM
Sound Forge Pro has a "Clipped Peak Restoration" tool.
iZotope Rx has a "Declipper" tool.
No guarantees with either of these but it's worth a try.

Mike
Former user wrote on 9/6/2010, 1:08 PM
I was downloading the demo version of Sound Forge Pro when your message posted. If it works then I have an excuse to spend some money on a new software package -- can't have too much software nowadays ;-)

Thanks!
rs170a wrote on 9/6/2010, 1:18 PM
If you're looking more for audio restoration than a full set of audio tools, I think most folks on here will agree with me when I say that you'll be hard pressed to beat iZotope.
I've heard some of what it's capable of and it amazes me.
Do a search on this forum and I'm sure you'll find some examples.

Mike
farss wrote on 9/6/2010, 1:28 PM
+1 for iZotope's Rx when it comes to fixing clipped or distorted audio.

Bob.
Former user wrote on 9/6/2010, 1:33 PM
Mike,

I found the "Clipped Peak Restoration" tool in SF but it's ghosted. Any ideas on how to access it?

Jim
rs170a wrote on 9/6/2010, 1:40 PM
Jim, did you bring in a file to work on?
If yes, maybe this is a limitation of the trial version?

Mike
Former user wrote on 9/6/2010, 1:48 PM
Being the trial version might be the issue. But, from what I've read there shouldn't be any limits other than the time it will operate.
Former user wrote on 9/6/2010, 1:54 PM
I just downloaded, installed and gave iZotope's Rx a try and it worked pretty well. The audio is still pretty rough, but I think some music might take care of masking the remaining issues.

Now I have to wait until my client gets back into their office tomorrow so I can let them know the issues and see if they want to increase their budget enough to cover the additional expense of "repairing" every sound bite they want used in the completed video.

As always, thanks for the help :-)
farss wrote on 9/6/2010, 2:03 PM
It's quite likely that what's happened to this audio is not hard digital clipping. It's pretty easy to overload the transmitter in wireless systems. That kind of analog clipping is impossible to fix in SF which simply looks for a series of samples at a defined value.
Don't ask me how Rx works its magic but it really is magic compared to what SF's tool can do.
You're probably just wasting your time even trying to get SF to fix your problem. It's OK if you have hard digital clipping of only 1 or 2 dB, beyond that it really cannot help much even with a lot of manual fiddling around. Rx seems to have the smarts to compute what got lost in the clipped parts, I take my hat off to them because I would have rated the task beyond impossible.

Bob.
AGB Productions wrote on 9/7/2010, 10:50 AM
Occasionally I've run into the same problem, someone who didn't record the sound with usable gain settings. Since SoundForge was all I had at my disposal, I isolated the area of interest, did the Clipped Peak restoration (normally set at -6 dB, no limiting), followed immediately by Click and Crackle Removal (normally using the "Remove lots of Crackle" default), followed by EQ, followed by Normalize. For some spoken word, this works "good enough." For some music, ditto.
Of course if the sound was WAY out of line (>6 dB), too bad, time to re-shoot it, after saying a few words in ancient Latin (I think that's the language!).