Methods to fix overmodulated audio?

Pullmanite wrote on 8/3/2005, 9:13 AM

I have several videos of a teacher who overmodulated the mic. His dynamics on the recording are over a huge range: everything from a faint whisper to full-blown yelling. :)

Well, during the loud portions, the mic is being overdriven... the recording levels are fine, but it's obviously distorted. Looking at the waveform, it's leveling out below the peak levels for the recording, so it looks like the audio was being attenuated somehow before it reached tape.

Anyway, I've tried boosting the volume a bit in order to hit the peak level on the audio, then doing some clipped audio restoration with the Sony Noise Reduction plugin. Results aren't that great. Any ways to improve what I've got to work with?

Thanks.

Comments

Chienworks wrote on 8/3/2005, 9:37 AM

Try running clipped peak restoration before increasing the volume. Clipped peak restoration needs some "space" to work with. By increasing the volume you are taking that space away.

Pullmanite wrote on 8/24/2005, 11:38 AM

Sorry it took so long to get back to you on this. I should have explained a bit better.

The microphone's gain was up too high, so either the mic or the camcorder attenuated the signal already. So the audio doesn't really peak at all... it just hits a flat ceiling at about 75% on the waveform. But it sounds distorted. The clipped peak restoration seems to work best if the audio actually peaks... not in this case.

I might need to look elsewhere for a way to reduce the distortion. The teacher has a huge dynamic range; goes from a whisper to a full-blown yell in a split second. :( I have Adobe Audition... any tricks I can try there?

rraud wrote on 8/24/2005, 11:55 AM

You may try taking some mid-range out with EQ... but there's not much that can be done in the case you describe. sorry
Learn more about proper gain staging and use a limiter next time.

drbam wrote on 8/24/2005, 8:09 PM

". . .use a limiter next time"

I agree. Use brickwall limiting. It's about the only way to capture this kind of material without problems.

drbam

PipelineAudio wrote on 8/25/2005, 9:23 PM

http://www.venganza.org
The Flying Spaghetti Monster sometimes reaches across the great gap and helps us mere mortals out. Praying to him is about the best way to deal with this.

Have you tried SF's clipped peak restorer? A lot of eq and some creative multiband compression can SOMETIMES help

farss wrote on 8/28/2005, 6:53 AM

Yes,
as noted previously Clipped Peak Restoration only works on hard digital clipping, if it got clipped in analogue land CPR will do nothing. Solution is to make it more clipped, add as little gain as needed to get flat tops. Give CPR enough headroom via the Reduce Gain Slider, I usually go for at least 6dB and apply post limiting.
Depending on how bad things were the results can vary from amazing to just acceptable.
Bob.

Pullmanite wrote on 8/31/2005, 8:39 AM

Thanks, farss... I tried that but must need to spend some more time tweaking it. Your last sentence there gives me some hope! :)

DustBunny wrote on 9/1/2005, 5:07 PM

farss, worked like a charm! I needed to be a bit more aggressive in boosting the gain, applied clipped peak restoration (worked best at -9 dB), then applied some slight compression and a hard limiter... and it was pretty amazing how well it worked. Thank you!

farss wrote on 9/2/2005, 5:43 AM

Glad I could help.
Bob.