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Canon GL Series DV Camcorders
Canon GL2, GL1 and PAL versions XM2, XM1.


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Old July 9th, 2004, 05:20 PM   #1
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Recording audio with a MIC

I waas considering this process for reconrding the dialogues (for short movie production) on the XM2:

connect the MIC (shotgun) to XM2's highest input, splitting the mono signal to the two channels.

set the level of the channels differectly:
-12 dBFS on a channel
-6 dBFS on another one

this would allow me to have the same signal recorder on the two channels with differect levels, allowing me to choose the best one in different moments: -12 dBFS signal when there are high volumes, for avoiding distorsions, for example when the actor is screaming, or a door is shut, -6 dBFS for parts where the volume is very low, and would otherwise be disturbed by the noise level of the camera, for example for parts of a dalogue when the actor is speaking at a very low volume, almost breathing.

I would then use normalizing and compression for composing a correct track, with correct dynamic, then taking it all to -10 dBFS (that's the level required by TV stations).

Is this all correct?

PS. I can't use and external recorder device instead of XM2 for the audio.
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Old July 10th, 2004, 07:14 AM   #2
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If your mic output level supports it, use the MIC ATT setting for a better signal to noise ratio.
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Old July 10th, 2004, 10:58 AM   #3
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Don,
I was wondering if I could run a MIC ATT question by you. I've been reluctant to try the MIC ATT at weddings out of fear that it might dampen my audio to much. Since it's impossible for me to test a wedding, I've been relying on riding the audio levels.

But, a problem almost always arises at ceremonies when levels are high for voices and the church lady suddenly sings or the organ music blasts away. Result...instant distortion. I'm currently using twin wireless lavs for all audio but will sometimes use one wireless and a Senn ME66 on-board. Will the MIC ATT stop the clipping without reducing fidelity?
Bob
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Old July 10th, 2004, 12:00 PM   #4
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<<<-- Originally posted by Don Palomaki : If your mic output level supports it, use the MIC ATT setting for a better signal to noise ratio. -->>>

Well yes, as I said, I'll use the highest level input on the XM2, that is, MIC input with MIC ATT on, that's -35 dBU, instead of -55 dBU.

Beyond this... the considerations I made are ok, right?
I mean, once I get the input signal with the best starting signal/noise ratio, it's a good thing optimize my digital recorded signals, considering the input will be mono (for dialogues), and I could this way have the best audio both on low and high volumes, right?
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Old July 11th, 2004, 07:20 AM   #5
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Bob - setup and do a test to see if it meets your needs. Round up a few friends to help with it. Many wireless have a fairly high output level, even at their MIC setting, as does the SENN ME66. If you are getting clipping now, MIC ATT will help a lot, and because the noise floor is lower, you can use more gain in post if needed to correct low levels.

Marco: Personally, I think you are going to a lot of trouble with only 6 dB difference in the channels (12 dB might be more effective), given how easy it is to do audio adjustment in post, but if it meets your needs, what you propose will work. But you cannot use AGC because it will effect both channels at the same time. based on the level in the louder channel.
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Old July 11th, 2004, 12:28 PM   #6
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<<<-- Marco: Personally, I think you are going to a lot of trouble with only 6 dB difference in the channels (12 dB might be more effective), given how easy it is to do audio adjustment in post, but if it meets your needs, what you propose will work. -->>>

Well, considering I only need mono audio for dialogues, I think having two slighty different version of the diaogues, one a little better for low volumes (it should be half volume, with 6 dB difference, right?) and the other one a little better for high volumes), with the possibility of doing cut and paste between the two, using normalization, gain and compressioon for getting the final volume and dynamic I need, could be a good thing.

Probably some tests are needed for finding the levels to use (i Think -12 for a channel is of, but there'žs maybe a better one for the other one, instead of -6...). I think -12 and -6 is a good compromise indeed.


<<<-- But you cannot use AGC because it will effect both channels at the same time. based on the level in the louder channel. -->>>

What's AGC?
Automatic Gain Chooser?
As I said, I want to try this tecnique setting my gain levels on the XM2 manually, using the independent audio gain knobs on the camera.
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Old July 11th, 2004, 06:41 PM   #7
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> What's AGC?

AGC = automatic gain control, also called ALC or automatic level control and even ARC, automatic record level. Basically the camcorder adjusts the gain to keep the average recorded autio level about 12 dB below max allowable digital record level.
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Old July 11th, 2004, 06:48 PM   #8
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Ah, ok, thanx! :-)
Anyway, as I said I would simply deactivate AGC and manually set one channel to -12 dBFS and the other one to -6 dBFS (or a different value), kepping the knobs fixed at their positions after setting them with the test tone.
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Old July 12th, 2004, 08:51 PM   #9
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Macro
I did just what you propose on a recent short. Used a ME66 on a boom into the GL-2 with the manual mic levels set pretty much as you propose for dialog. I'm now finishing post and it has saved my backside a couple times to take the lower channel only when the mic was overdriven into the louder channel. Also you can create some nice stereo audio positioning by using both channels and keeping the hotter one on the side of the screen where the speaker is--if they dont match just flip the channels. Too bad I didn't discover the value of using the mic att switch with such a hot mic until the last day of production. But I'll know better for next time.....
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Old July 13th, 2004, 01:40 AM   #10
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MIC ATT is for me too. It is superb.

3 weeks ago I did a shoot where the woman was speaking into a PA - I couldn't get near the loudspeakers - but, although her voice was "soft", well almost non-existent, and once I got the audio of her speech into Sony's Sound Forge I had plenty of information to doctor-up and resynch. Worked very well indeed. The point I'm making is that it is better that the audio is "soft" than clipped and overly hot. You can't do much with that. Okay the lifted background hum and noise levels I removed with Sony's Noise Reduction and I re-ramped it all with her own EQ profile - worked great!

. .and yes SENN ME66 here too .. .

Grazie
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