Auto Gain Control

K

Kevino

New member
Hi list,

A very basic quesion but I could really use some help.

I would like to set the audio to auto on my DVX-100.

Shooting event video I put the camer ani auto mode and under AUTO SW in the menu, I have AGC set to -6DB.

But I see that the levels still peak out and I have bad clipping in louder sections.

Is there something I'm doing wrong?

I'd be really grateful for any pointers as this has taken weeks to rescue distorted audio.

Warmest,


K.
 
Kevino,

AGC on the DVX is VIDEO gain - no effect on audio at all.

There is an auto audio limiter on the DVX called ALC, however. Go into menu, recording setup, find ALC and switch it to "ON" if it isn't there already.

That setting only limits, it does nothing to boost low audio.

On a similar note, the audio levels meter (in the viewfinder / lcd) goes from white to red at -12db. In digital audio, clipping and distortion do not start until 0db. That means you can see the meter go into the "red zone" on the DVX but no distortion will take place until it hits 0db, so it's OK to run in the red as long as you do not hit 0db. The limiter should help you there but it's always best to set levels properly.

Most "pro" audio level meters have 3 colors (usually green, orange/yellow, and red) to denote where the "caution area" (orange/yellow) is, and the "red zone" is used in those devices to signal distortion is or may be happening. The better units also have a clip light to signal when distortion takes place. Unfortunately, the DVX meter is not the same.

Having said that, I would also say that you must be mindful of the dynamic audio range you are shooting. It is always best to do a "sound check" of the shot to allow proper audio level settings with the round level dials below the LCD.

6db is what the human ear perceives as a doubling of volume level so you only have 2 perceived doublings in volume before distortion if you set the average levels at -12db (which is the average level to adjust for for). This should be enough for "normal" dynamic range, but going from a whisper to loud scream exceeds that.

Ken :)
 
Last edited:
Barry,

Thanks!

Glad to help where I can.

I'm waiting to receive your book (from the rebate package) so I can really dig in to the video end of things.

Ken :)
 
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