Fixing Audio Distortion

[Doug Lange]

OK, time to sit on the deck and drink a few cold ones, whether it's beer or iced coffee. (I make a wicked cold-brewed ice coffee with the Toddy Coffee maker.) I've got a great looking little acre lot, snuggled against a birch forest. Nothing finer than Summer in Alaska:-)

When in a perfect world, we get perfect audio. Last week I was doing backup recording of a small chior in a concert hall. The ventilation didn't get turned off. We were riding the levels hot, too, because there were only 8 voices. The house Neumann's clipped on a loud part, dispite the $$ in equipment. Clipping happens. At least I have my goofy recording using an iPod, Mackie 1202 and 2 AKG Blue Lines to add to the messy audio;-) Yes, that's a crazy setup. I wanted to test the limits of an iPod recorder with the AKGs. I'll post the audio just for fun.

Well, time to throw a few rib-eyes on the BBQ. How many should I throw on for us?

[Mark Harmer]

Originally Posted by Alex Thames

for audio that is already recorded badly and can't be re-recorded, I think the point of this thread was to come up with ways to improve or fix the clipped audio.

Alex,

If you haven't got this sorted, I'm emailing you with my email address and you can send the offending audio to me. I'll see what I can do with it.

Mark

[Ty Ford]

Even better, if this was a staged performance, see if the yell from another take will work.

There's a great piece of software called Vocalign that does a pretty amazing job of realigning (time compressing and expanding) the good take to fit the timing of the bad take. I've seen/heard it; what a life saver. The industry has been using it for years. I wrote an article about it about 10 years ago. At that point the guys in Hollywood said Vocalign was cutting ADR sessions to 30% of what they had been because they were able to use other takes a lot of the time and sync them with Vocalign.

Regards,

Ty Ford

PS Adobe's Audition has been mentioned as a passsable declipper, but most of the reports I've heard say it sort of works, but leaves it's own residue. That's why I didn't mention it earlier. (No one else has either, which tends to make me think it's not really up to the job either) Anyone??

[Mark Harmer]

Originally Posted by Ty Ford

Adobe's Audition has been mentioned as a passsable declipper, but most of the reports I've heard say it sort of works, but leaves it's own residue. That's why I didn't mention it earlier. (No one else has either, which tends to make me think it's not really up to the job either) Anyone??

I use Audition quite a lot and was intrigued by Ty's question above. So I ran a comparison between Audition's clip restoration and the Sony plugin. I amplified a piece of audio by 17db, leaving it mostly clipped, duplicated it and and then ran one through Adobe Audition's inbuilt clip restoration and the other through Sony 2.0's clip restoration plugin (both using Adobe Audition as the base software - this won't affect the comparison between the two plugins). Both plugins had the same attenuation setting. The restored audio tracks came out pretty similar. Adobe Audition's effort did leave one particular strange artefact in just one place, but otherwise I'd say there wasn't much to choose between them. I prefer Adobe audition's plugin because I'm used to it, and it has more user-controllable settings and will produce statistics for you as well. Neither managed to restore the quality of the original but the restored audio was usable.

Digital clipping is a severe effect but also one that software can calculate and at least partially restore. However that's a bit different from my experience of some of the stuff that happens in acquiring sound on a camera. When I first started using my XHA1 with a Sennheiser shotgun mic I always thought it sounded a bit "rough". Then we did one shoot which had quite badly distorted audio even though my colleague said she set the record level set to manual and the meters were looking fine (we were shooting in the middle of a children's playgroup and for safety reasons weren't monitoring on headphones).

In a quiet area, we put the mic on the camera and tried some voice tests, and it still had that subtle "rough" quality - it didn't matter what we did with the level controls or whether the camera was in auto or not. The only thing that cured it - completely - was putting the attenuation in, which for quiet speech I had simply assumed wasn't necessary. I came to the conclusion that this was analogue overload distortion in the camera mic input stages. In the case of the video we shot, the clip restoration plugin didn't make any difference to it. We went back and re-shot this particular piece and now I always use the pad in all but the quietest situations and the sound is a lot cleaner.

For those XHA1 users out there, take a few minutes to do some tests with your mic and don't rely on the meter as I was getting distortion even with the meters only peaking halfway up. If it sounds rough, try it with the pad. The XHA1's inputs seem more than usually sensitive - but are also very good quality and low-noise if set up properly.

[Belinda Bowey]

Originally Posted by Mark Harmer

Alex,

If you haven't got this sorted, I'm emailing you with my email address and you can send the offending audio to me. I'll see what I can do with it.

Mark

Hi Mark,

I have a file of bad audio from one of my videographers getting a live feed from a band, the connection was dodgy and kept peaking, am l also able to email you a link to listen to it ???

Belinda

[Paul R Johnson]

Belinda - you did notice he asked the question FIVE YEARS AGO?

[Colin McDonald]

Well, it was in a very big building (long echo)
:-)

[Greg Miller]

Originally Posted by Paul R Johnson

Belinda - you did notice he asked the question FIVE YEARS AGO?

Ah, there's the rub. We ask people to search the archives before asking a question that's been asked and answered previously. So they search the archives, and indeed they find an old thread that's appropriate. Then they append their new question to the old thread, and are [gently] chastised for their efforts.

Or, to condense: some days you just can't win.

[Allan Black]

Belinda, start a new thread and post your link here, we can start again and link back to this thread, there'll be feedback like you wouldn't believe.

Cheers.