Help with over modulated audio.... at DVinfo.net

Peter Vaughn · November 15th, 2006, 07:51 AM

Hi there everyone...I'm having lots of trouble tweaking an over-modulated interview that is airing on television in the next month. I'm using VEGAS 6, is there a special plug in, or a specific way to use SOUND FORGE to help negate the over modulation?
Any help would be greatly appreciated.
Peter Vaughn

A. J. deLange · November 15th, 2006, 09:59 AM

Not sure what is meant by "over modulated". Does this mean that a wireless mic was used and the transmitter over driven? Or does it mean that the gain control on the recorder was set too high and the signal was consequently clipped? In either case the situation isn't great. With the wireless it might (and I emphasize "might") be possible to construct the inverse of the effective transfer function (as the limiting will be soft) and run the recorded signal through it thus removing some of the distortion. For clipping (hard limiting) laborious manual reconstruction of the rounded parts of the flattened peaks (provoded the clipping isn't too bad) might improve things. Apple's Soundtrack Pro has a filter which is supposed to fix clipping but I don't know how effective it is. Heroic endeavor by an experienced speech processing engineer might be able to extract the formant frequencies and use them to drive a vocal tract model but you won't get this done in a month.

Peter Vaughn · November 15th, 2006, 10:08 AM

Yes, a wireless mic, passing through a mixer, was over driven somehow.
So there really aren't any short cuts?

Don Bloom · November 15th, 2006, 10:10 AM

If you mean too loud but not clipped, then there are about 6 fdifferent ways in Vegas to fix it. Clip level, track level, bus level, master level an of course a level envelope across the clip(s) and track. A combination of these OR use the Vegas Non real time FX and try Amplitude modulation OR volume to adjust or again a combination.
If however the audio is clipped, then you've got a real problem BUT it might be able to be improved however it won't be perfect. Copy the audio and place on another track, split the tracks meaning use the BEST channel (left or right) from both copies and then use an envelope to lower the levels, and perhaps try a graphic EQ to adjust the sound then use a PAN envelope to set one to the right and one to the left. It will certainly take some playing around with to "fix" it but keep in mind that you can't fix whats not there. If it's clipped it's gone. You might need a de-esser or to kill some of the top end with the eq but again you need to play with it a bit.

HTHs

Don

Bill Ravens · November 15th, 2006, 10:11 AM

soundforge has a utility to both search for and repair clipped peaks. sometimes it works. i've also been able to do limited repair of overdriven signal by applying heavy compression to the signal.

November 15th, 2006, 07:51 AM	#1
Peter Vaughn Regular Crew Join Date: Sep 2006 Location: Milford Michigan Posts: 38	Help with over modulated audio.... Hi there everyone...I'm having lots of trouble tweaking an over-modulated interview that is airing on television in the next month. I'm using VEGAS 6, is there a special plug in, or a specific way to use SOUND FORGE to help negate the over modulation? Any help would be greatly appreciated. Peter Vaughn

November 15th, 2006, 10:08 AM	#3
Peter Vaughn Regular Crew Join Date: Sep 2006 Location: Milford Michigan Posts: 38	Over Modulated sound... Yes, a wireless mic, passing through a mixer, was over driven somehow. So there really aren't any short cuts?

November 15th, 2006, 09:59 AM	#2
A. J. deLange Major Player Join Date: Jun 2004 Location: McLean, VA United States Posts: 749	Not sure what is meant by "over modulated". Does this mean that a wireless mic was used and the transmitter over driven? Or does it mean that the gain control on the recorder was set too high and the signal was consequently clipped? In either case the situation isn't great. With the wireless it might (and I emphasize "might") be possible to construct the inverse of the effective transfer function (as the limiting will be soft) and run the recorded signal through it thus removing some of the distortion. For clipping (hard limiting) laborious manual reconstruction of the rounded parts of the flattened peaks (provoded the clipping isn't too bad) might improve things. Apple's Soundtrack Pro has a filter which is supposed to fix clipping but I don't know how effective it is. Heroic endeavor by an experienced speech processing engineer might be able to extract the formant frequencies and use them to drive a vocal tract model but you won't get this done in a month.

November 15th, 2006, 10:10 AM	#4
Don Bloom Inner Circle Join Date: Jan 2003 Location: Chicago, IL Posts: 6,609	If you mean too loud but not clipped, then there are about 6 fdifferent ways in Vegas to fix it. Clip level, track level, bus level, master level an of course a level envelope across the clip(s) and track. A combination of these OR use the Vegas Non real time FX and try Amplitude modulation OR volume to adjust or again a combination. If however the audio is clipped, then you've got a real problem BUT it might be able to be improved however it won't be perfect. Copy the audio and place on another track, split the tracks meaning use the BEST channel (left or right) from both copies and then use an envelope to lower the levels, and perhaps try a graphic EQ to adjust the sound then use a PAN envelope to set one to the right and one to the left. It will certainly take some playing around with to "fix" it but keep in mind that you can't fix whats not there. If it's clipped it's gone. You might need a de-esser or to kill some of the top end with the eq but again you need to play with it a bit. HTHs Don

November 15th, 2006, 10:11 AM	#5
Bill Ravens Join Date: Nov 2001 Location: santa fe, nm Posts: 3,264 Images: 10	soundforge has a utility to both search for and repair clipped peaks. sometimes it works. i've also been able to do limited repair of overdriven signal by applying heavy compression to the signal.