AGC Defeat question at DVinfo.net

G. Lee Gordon · June 15th, 2010, 08:41 PM

I've been filming several interviews in a studio with the mic plugged in directly into the T2i and have been very satisfied with the results. I recently took it on the street for some OTS interviews and the sound would randomly cut in and out. Is this the AGC function everyone is complaining about?

James Donnelly · June 16th, 2010, 07:09 AM

If you mean by that what is described as pumping, where AGC kicks in to raise the gain when nothing much is happening, resulting in background noise being heard at loud volumes, then yes.

But the way you phrase it, cutting in and out, it doesn't sound like AGC. Can you be more specific?

G. Lee Gordon · June 18th, 2010, 04:02 PM

Out on the streets, when the wind started to blow the sound would cut off. I've never experienced that before. That is why I was wondering if that was due to the AGC function.

Bruce Foreman · June 18th, 2010, 09:10 PM

Yes. The wind "scraping" across the mic holes can be a loud enough noise and the AGC cuts the recording gain suddenly. Two ways to try to get around this are the use of an external mic with furry windmuff (will help but may not completely eliminate "pumping") or the use of an external audio recorder like the ZoomH2 or ZoomH4n (both also with furry windmuff - available from thewindcutter.com).

I actually often use both at once, the Rode SVM with "Deadcat" windmuff on the camera plugged into the mic input and my ZoomH2 with windmuff on a stand out in front of the cam and as close to the talent as I can get it without it showing in the picture.

The camera audio is mainly for synchronization when I position the WAV audio from the ZoomH2 on a separate audio track in the editing package. I synch on the command "Action" for each scene by aligning the waveforms. When it's right and sync looks good I mute the camera audio and trim each scene where I need for "in" and "out" points.

The camera audio can also be a "backup" in case the Zoom audio went south.

For good audio you almost have to use an external audio recorder with these DSLRs.

June 15th, 2010, 08:41 PM	#1
G. Lee Gordon Major Player Join Date: Aug 2003 Location: Dallas, TX Posts: 431	AGC Defeat question I've been filming several interviews in a studio with the mic plugged in directly into the T2i and have been very satisfied with the results. I recently took it on the street for some OTS interviews and the sound would randomly cut in and out. Is this the AGC function everyone is complaining about? __________________ "Get Er Done!!!"

June 18th, 2010, 04:02 PM	#3
G. Lee Gordon Major Player Join Date: Aug 2003 Location: Dallas, TX Posts: 431	Out on the streets, when the wind started to blow the sound would cut off. I've never experienced that before. That is why I was wondering if that was due to the AGC function. __________________ "Get Er Done!!!"

June 16th, 2010, 07:09 AM	#2
James Donnelly Major Player Join Date: Apr 2010 Location: Chelmsford England Posts: 287	If you mean by that what is described as pumping, where AGC kicks in to raise the gain when nothing much is happening, resulting in background noise being heard at loud volumes, then yes. But the way you phrase it, cutting in and out, it doesn't sound like AGC. Can you be more specific?

June 18th, 2010, 09:10 PM	#4
Bruce Foreman Trustee Join Date: Nov 2006 Location: San Angelo Texas Posts: 1,518	Yes. The wind "scraping" across the mic holes can be a loud enough noise and the AGC cuts the recording gain suddenly. Two ways to try to get around this are the use of an external mic with furry windmuff (will help but may not completely eliminate "pumping") or the use of an external audio recorder like the ZoomH2 or ZoomH4n (both also with furry windmuff - available from thewindcutter.com). I actually often use both at once, the Rode SVM with "Deadcat" windmuff on the camera plugged into the mic input and my ZoomH2 with windmuff on a stand out in front of the cam and as close to the talent as I can get it without it showing in the picture. The camera audio is mainly for synchronization when I position the WAV audio from the ZoomH2 on a separate audio track in the editing package. I synch on the command "Action" for each scene by aligning the waveforms. When it's right and sync looks good I mute the camera audio and trim each scene where I need for "in" and "out" points. The camera audio can also be a "backup" in case the Zoom audio went south. For good audio you almost have to use an external audio recorder with these DSLRs.