appeal for help with distorted clip at DVinfo.net

Bill Ball · July 26th, 2004, 08:55 AM

I have a distorted audio clip and I have reached the end of my very limited knowledge of audio post. So I am appealing for help from this list. I read Jay’s post book while preparing this project and tried several things on my own but with no luck. It’s the final piece of post on this particular project so I thought I would check for advice here before giving up and living with it.

The clip was recorded outdoors on a Senn. ME66 into a GL-2 over the Shure adapter. One channel was set a little higher than the other. The actor was holding the mic, covered by a Rycote softie, about two feet from his mouth. The mic attn switch was not used.

I tried to be very careful to not let the audio get clipped by using the manual controls on the camera. Working in Adobe Audition 1 (aka Cool Edit) the waveform does not appear to be clipped. Yet the audio sounds like it is pretty heavily clipped.

I suppose the mic may have been overloaded before encountering the level controls in the camera?

At any rate, my question is whether there is anything the can be done in post (using Audition) to improve the situation.

I put a copy of the original waveform (16 bit 48k from the avi file) online at:

http://ball.tcnj.edu/distorted_clip.wav

In case anyone wants to give it a listen. Its about 9 meg.

Bill Ball

Jay Massengill · July 26th, 2004, 10:41 AM

The MicATT switch probably would have saved you. Unless the actor was screaming (I haven't listened to the clip) then it's most likely a case of this hot mic overloading a regular mic input rather than the mic itself overloading. This mic can be overloaded by loud crowds or other sounds that come from all directions at once, but that would be less likely with just one actor.
The regular mic input will always run out of headroom before the mic does even in a situation loud enough to overload the mic.
The MicATT switch or an external attenuator is a very necessary accessory for the K6/ME66 and other hot mics.

As you've already seen, the meters won't be an accurate guide when the mic input gets overloaded. You must monitor the audio and listen for distortion and take steps to correct it. With many cameras with poor headphone circuits this is not always an easy task. You can rig up extra equipment and use the line outs from the camera or you can use a heaphone amp and invest in very good sensitive headphones.

Now on to your problem. There isn't a tremendous amount you can do to fix a clip with heavy distortion. Have you tried rolling off the high frequencies? Do you have music or some other suitable sound for the visuals to put under it?
Does this clip require lipsync? If not then re-record it. Even if it does require lipsync, since it's only one clip you can work with the actor and replace it without too much time or difficulty. If this is a possibility then I'll give more details about how to use your NLE for setting this up. If the actor isn't available, then there isn't much else to do.
You could post this on DV.com where Jay himself gives advice on EQ, multiband compression and other techniques.

Matt Gettemeier · July 26th, 2004, 01:17 PM

I listened to the clip. Did you already split the channels, duplicate the lower channel, thereby dumping the higher channel?

I wouldn't call it totally wasted, but the emotion of the performance is lost from it... so I hear your frustration.

Douglas Spotted Eagle · July 26th, 2004, 01:22 PM

Bill, aside from Matt's recommendation, have you got access to Sony's Noise reduction tool? Their "Clipped Peak" restoration tool does a decent job of recovering audio that is recoverable.

I can't listen to the clip, I'm on a dialup and not about to access 9 meg...

Mike Rehmus · July 26th, 2004, 06:30 PM

I ran statistics on the sample.

Some DC offset was present. I removed it but that didin't change the sound. I tried various filters but the Clipped Peak restoration worked best. It is better but not perfect.

The original file sounded like a person talking without clearing their throat. Now it sounds clearer.

I'd guess you just overloaded the microphone elements as the signal isn't anywhere near clipping levels and shows no signs of having been clipped.

Bill Ball · July 26th, 2004, 06:39 PM

Thanks for the input so far gang.

Mike --could you give me a crack at getting your altered version of the file back?

The clipped filter in Audition didnt seem to do much. Although I saw a demo of Audition 1.5 and it looks a lot more powerful.

At any rate, I'd like to give your version a try. I can't offer you anything other than a thank you in the credits since this is for a no-budget hobby project. I'll eventually post a streaming version of the short online and would be happy to send a DVD as well.

The MicATT stays on in the future with that mic.

Bill

July 26th, 2004, 08:55 AM	#1
Bill Ball Major Player Join Date: Jan 2004 Location: NEW JERSEY Posts: 216	appeal for help with distorted clip I have a distorted audio clip and I have reached the end of my very limited knowledge of audio post. So I am appealing for help from this list. I read Jay’s post book while preparing this project and tried several things on my own but with no luck. It’s the final piece of post on this particular project so I thought I would check for advice here before giving up and living with it. The clip was recorded outdoors on a Senn. ME66 into a GL-2 over the Shure adapter. One channel was set a little higher than the other. The actor was holding the mic, covered by a Rycote softie, about two feet from his mouth. The mic attn switch was not used. I tried to be very careful to not let the audio get clipped by using the manual controls on the camera. Working in Adobe Audition 1 (aka Cool Edit) the waveform does not appear to be clipped. Yet the audio sounds like it is pretty heavily clipped. I suppose the mic may have been overloaded before encountering the level controls in the camera? At any rate, my question is whether there is anything the can be done in post (using Audition) to improve the situation. I put a copy of the original waveform (16 bit 48k from the avi file) online at: http://ball.tcnj.edu/distorted_clip.wav In case anyone wants to give it a listen. Its about 9 meg. Bill Ball

July 26th, 2004, 01:22 PM	#4
Douglas Spotted Eagle VASST Join Date: Jan 2004 Location: Stockton, UT Posts: 5,648	Bill, aside from Matt's recommendation, have you got access to Sony's Noise reduction tool? Their "Clipped Peak" restoration tool does a decent job of recovering audio that is recoverable. I can't listen to the clip, I'm on a dialup and not about to access 9 meg... __________________ Douglas Spotted Eagle/Spot Author, producer, composer Certified Sony Vegas Trainer http://www.vasst.com

July 26th, 2004, 06:30 PM	#5
Mike Rehmus Wrangler Join Date: May 2002 Location: Vallejo, California Posts: 4,049	I ran statistics on the sample. Some DC offset was present. I removed it but that didin't change the sound. I tried various filters but the Clipped Peak restoration worked best. It is better but not perfect. The original file sounded like a person talking without clearing their throat. Now it sounds clearer. I'd guess you just overloaded the microphone elements as the signal isn't anywhere near clipping levels and shows no signs of having been clipped. __________________ Mike Rehmus Hey, I can see the carrot at the end of the tunnel!

July 26th, 2004, 10:41 AM	#2
Jay Massengill Trustee Join Date: Jul 2003 Location: Burlington Posts: 1,976	The MicATT switch probably would have saved you. Unless the actor was screaming (I haven't listened to the clip) then it's most likely a case of this hot mic overloading a regular mic input rather than the mic itself overloading. This mic can be overloaded by loud crowds or other sounds that come from all directions at once, but that would be less likely with just one actor. The regular mic input will always run out of headroom before the mic does even in a situation loud enough to overload the mic. The MicATT switch or an external attenuator is a very necessary accessory for the K6/ME66 and other hot mics. As you've already seen, the meters won't be an accurate guide when the mic input gets overloaded. You must monitor the audio and listen for distortion and take steps to correct it. With many cameras with poor headphone circuits this is not always an easy task. You can rig up extra equipment and use the line outs from the camera or you can use a heaphone amp and invest in very good sensitive headphones. Now on to your problem. There isn't a tremendous amount you can do to fix a clip with heavy distortion. Have you tried rolling off the high frequencies? Do you have music or some other suitable sound for the visuals to put under it? Does this clip require lipsync? If not then re-record it. Even if it does require lipsync, since it's only one clip you can work with the actor and replace it without too much time or difficulty. If this is a possibility then I'll give more details about how to use your NLE for setting this up. If the actor isn't available, then there isn't much else to do. You could post this on DV.com where Jay himself gives advice on EQ, multiband compression and other techniques.

July 26th, 2004, 01:17 PM	#3
Matt Gettemeier Major Player Join Date: May 2003 Location: St. Louis, Missouri Posts: 936	I listened to the clip. Did you already split the channels, duplicate the lower channel, thereby dumping the higher channel? I wouldn't call it totally wasted, but the emotion of the performance is lost from it... so I hear your frustration.

July 26th, 2004, 06:39 PM	#6
Bill Ball Major Player Join Date: Jan 2004 Location: NEW JERSEY Posts: 216	Thanks for the input so far gang. Mike --could you give me a crack at getting your altered version of the file back? The clipped filter in Audition didnt seem to do much. Although I saw a demo of Audition 1.5 and it looks a lot more powerful. At any rate, I'd like to give your version a try. I can't offer you anything other than a thank you in the credits since this is for a no-budget hobby project. I'll eventually post a streaming version of the short online and would be happy to send a DVD as well. The MicATT stays on in the future with that mic. Bill