Some distortion in my soundfiles - Page 2 at DVinfo.net

Go Back   DV Info Net > The Tools of DV and HD Production > All Things Audio

All Things Audio
Everything Audio, from acquisition to postproduction.


Reply
 
Thread Tools Search this Thread
Old October 11th, 2007, 02:39 AM   #16
Inner Circle
 
Join Date: Feb 2007
Location: Fairfield, Dunedin, New Zealand
Posts: 3,634
Images: 18
Yep.............

If it is, indeed, clipping, it is impossible to "fix".

It is possible to ameliorate (make better) but not possible to replace that which has been lost.

As I said, someone is going to home in here and give you that magic bullet to "ameliorate" it, but fix totally, no, it is simply not possible.

Figure out where it's happening and nail it, once and for all, before you shoot any more stuff that is important. Once the info's gone, it's gone.

CS
Chris Soucy is offline   Reply With Quote
Old October 11th, 2007, 04:30 AM   #17
Major Player
 
Join Date: Aug 2006
Location: Petaluma, CA
Posts: 456
I have good news and bad news

Quote:
Originally Posted by Arvid Unsgaard View Post
The strange thing is that it not get clipped in the camera.
Hi Arvid,

First the good news - I don't think your problem is clipping. I looked at the waveform on the first clip (church singing) and the signal looks fine. If you had a clipping problem, the wavetops would not be smooth sinusoidal tops but instead would look like flat-top mountains. You see, clipping distortion flattens audio waves - once the analog to digital conversion reaches peak, everything above the max is simply all digital ones. But your waveform doesn't have flat-tops, so you don't have a clipping problem. Here's a simple explanation of the A-D quantizing problem. Let's say I have 5 binary digits to guess anyone's age: the digits are 16-8-4-2-1. Your age is 29, in our base 10 that's 16+8+4+x+1, or in digital it's 11101. Now let's do your son who is 7 years old: he's 0+0+4+2+1, or digitally 00111. So far, so good. Now let's try your 52 year old dad - oops, the highest we can go is 16+8+4+2+1 (31 years old), or digitally 11111. And how about your grandfather? Again, 31 is tops, or 11111. You see the problem? Once our A-D converter makes all ones (flat-top square wave), anything higher is still all ones. Clipping (maxing or pegging the meter in red) is not desirable. For those in the know, we call this quantization error (running out of binary digits).

Anway, perhaps part of your problem was that your microphone was too far away from the talent. In that case, perhaps you turned up the audio gain to compensate for the problem. Unfortunately, you're picking up a lot of reflected waves bouncing off floors, walls, etc before reaching your microphone. At any rate, like the clipping problem your options are limited. But perhaps you might try filtering out some of the high frequency audio (low pass filter) which might sound a bit more pleasing.

My second concern was running a mixer output (hot line level signal, 50K ohm high impedence) directly to your PD170 (requires weak microphone level signal, 600 ohm low impedence). Perhaps you shut down the PD170 amplifier gain to try to compensate for the signal mismatch, but I'm guessing you've got an impedence mismatch problem.

Next time you may want to try something like the Matchbox DB25:
http://media.zzounds.com/media/db25m...082f6c8864.pdf

Finally, if the audio sounded better in the camera, I'd guess the problem just isn't as perceptible - the camera speaker isn't a good test. If you aren't doing so already, be sure to wear a good set of headphones while monitoring the audio.

Good luck, Michael
Michael Nistler is offline   Reply With Quote
Old October 11th, 2007, 02:49 PM   #18
Regular Crew
 
Join Date: Sep 2007
Location: sweden
Posts: 38
Hi! Michael!

What can I say, you are awesome. I learn everytime im here.

Thanks.


Arvid
Arvid Unsgaard is offline   Reply With Quote
Old October 11th, 2007, 05:58 PM   #19
Major Player
 
Join Date: May 2007
Location: Toronto, Ontario, Canada
Posts: 287
Quote:
Originally Posted by Arvid Unsgaard View Post
I use the 0db peep to adjust the volume on the camera and then listen all the time on the camera sound.
Arvid, when you use the 0 dB 1 Khz tone from your Shure FP24 mixer, are you adjusting the sound level of the camera to -12 dB ?

Digital recording devices ( including cameras ) have no "head-room" past 0 dB ( any sound louder than 0 dB on your camera may cause clipping distortion ), so normally you would record the 0 dB tone from your mixer at -12 dB on your camera so that you will have an extra 12 dB of "head-room" when you record.

Also, are you using high-quality headphones to monitor the sound you are recording with your camera?

Sony 7506 headphones are pretty much the standard for monitoring sound for video.
Guy McLoughlin is offline   Reply With Quote
Old October 12th, 2007, 02:31 AM   #20
Regular Crew
 
Join Date: Sep 2007
Location: sweden
Posts: 38
Thanks for all your help.

Ok, so I have some problem with my sound, not all the time but...

Yesterday I download waves that have something called clip restoration.

But what do you think i can do to make it better.

I found this:

http://www.mindspring.com/~mrichter/formula/formula.htm

Which tool step by step can I use to get it better, or sounds better?
Arvid Unsgaard is offline   Reply With Quote
Old October 12th, 2007, 02:32 AM   #21
Regular Crew
 
Join Date: Sep 2007
Location: sweden
Posts: 38
Quote:
Originally Posted by Guy McLoughlin View Post
Arvid, when you use the 0 dB 1 Khz tone from your Shure FP24 mixer, are you adjusting the sound level of the camera to -12 dB ?

Digital recording devices ( including cameras ) have no "head-room" past 0 dB ( any sound louder than 0 dB on your camera may cause clipping distortion ), so normally you would record the 0 dB tone from your mixer at -12 dB on your camera so that you will have an extra 12 dB of "head-room" when you record.

Also, are you using high-quality headphones to monitor the sound you are recording with your camera?

Sony 7506 headphones are pretty much the standard for monitoring sound for video.
I use a headphone that came with the mixer - I dont know the name.
Arvid Unsgaard is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > The Tools of DV and HD Production > All Things Audio

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 04:09 PM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network