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Old June 3rd, 2005, 10:38 AM   #1
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Audio dummy needs help understanding specs

I own a JVC GY-DV500U. The camera has two XLR jacks. The specifications for the camera read...
"16-bit, 48kHz, 2-channel PCM audio/12-bit, 32kHz, 2-channel PCM audio"

The problem I'm having is this... A local band wants me to show up at their next concert and video tape them doing their deal. They want me to tie directly into their mixer. At a pre-production meeting a big discussion ensued about the audio capabilities of my camera. I was under the impression that each input on the back of my camera could carry a stereo signal. After reviewing the manual, however, we thought that maybe each jack was capable of only carrying a mono signal.

Hence the confusion... Is the camera capable of supporting 4 channels (a left and a right on Channel 1 & a left and a right on Channel 2), or 2 channels (a monaural input on Channel 1 & a monaural input on Channel 2).

Here's a link to the camera's PDF manual. http://books.jvcservice.com/download...1035/28765.pdf

Any help would be greatly appreciated!
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Old June 3rd, 2005, 11:52 AM   #2
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As I read your manual, you can record 2 channels of audio on the tape and the camera has two sets of inputs, the Ch1/Ch2 mike inputs in front for the built-in microphone and Ch1/Ch2 audio inputs on the rear. Each half of each pair can be selected independently. Channel 1 on the tape can receive either Front 1 or Rear 1. Channel 2 on the tape can receive either Front 2 or Rear 2. But I don't see anything to suggest that it's possible to record 4 channels of audio on the tape with your camera, even though the DV spec does permit 4 and some cameras, like the XL2, can record on all 4 (but at some loss of quality). The rear inputs can be selected for either line level or microphone level signals. If you record mono, you can send the signal to either recording channel 1 or recording channel 2 depending on which input you plug into or with an external mixer to split the mike signal into two feeds you can send it to both of them at once. If you record stereo, the left signal would go to Audio Channel 1 and the right signal to Audio Channel 2.

Since dialog is usually mono in the final mix, fed equally to left and right or the left, right, and centre, and recorded with either lavs or a shotgun mike just out of frame pointed at the talent instead of the on-camera mike, some writers suggest recording the same feed on both channels. Your external microphones would feed a small portable mixer and from there into the camera. The mixer would let you combine the one or more incoming mike signals into one mono signal, then split that in the mixer to feed identical signals out of both its L & R line outs. Feed those into the Ch1 & Ch2 rear inputs on your camera. Record the Left channel, Ch1, with the camera's meters hitting just under 0db on the peaks. Record the Right channel, Ch2, with the peaks hitting -20dB, much lower. That way if there's an unexpected super loud sound that would overload and distort the main recording, you have an insurance duplicate on the other channel that's not overloading and you can pick the best one to use when you edit.

Steve
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Old June 3rd, 2005, 12:03 PM   #3
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After posting my note and then re-reading your message, to clarify it looks like you can accomodate one stereo signal, the left channel output from the band's mixer recording on audio channel one and the right channel from the mixer going to audio channel 2. The two options in the spec you quoted are an "or" condition, not an "and" condition, meaning you have a choice of recording either 16 bit or 12 bit audio (go with 16 bit for the higher quality, there'd be no advantage to 12).
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Old June 3rd, 2005, 01:03 PM   #4
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This answer is MOST helpful! Thank you so much!
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Old June 3rd, 2005, 02:04 PM   #5
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As Steve points out, you could take a stereo output (2 channels) from their mixer and feed it into your camera.

One thing to watch out for is that the feed may not be very good. It probably won't have any audience noise, so that may seem a little weird. As well, the mix may not include all the instruments you need.

There are some posts on the forum about this. You may want to use a seperate recorder for the mixer feed or for the audience, while your camera records the other.
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Old June 3rd, 2005, 02:14 PM   #6
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A few other points about this camera:
The front low-mounted volume wheel can still affect the audio recording level even if you've disabled it using the rear menu. Make sure it's at "10" and tape it down if you are using the rear volume controls for a stereo line-level feed from a mixer.
The front mic input phantom power is turned on or off using the front menu.
The low-cut filters for both audio channels are turned on or off in one of the menus.
If you want a single mic to be recorded to both channels, you must use the front input. This input is mic level only.
The rear inputs have 3 switch settings, MIC/MIC Phantom On/LINE. There is no MIC ATTenuate setting. If you use condenser mics in a loud situation, you can overload these mic inputs and the recording level controls won't help.
I would use the LINE input setting and an external mixer feeding the two rear inputs with balanced XLR connections.
This camera has pretty clean audio, but it is sensitive to dynamic sounds. I would record with peaks around -12db to -10db and listen carefully for distortion on the peaks.
Be aware that the band's output from their mixer will be set up for their PA system and not necessarily optimized for video recording. I will often use a separate mixer that uses the direct outputs from their mixer to give duplicate but separate EQ and control. Add your own ambient mics to this mixer to get a more open sound that includes audience reaction, etc.
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Old June 4th, 2005, 04:05 PM   #7
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Amazing. I can't tell you how impressed (and happy) I am with everyone's feedback.

Jay, I had NO idea that the level setting of the front jack could effect the levels on the rear jacks. I just checked the camera and found the front wheel at "2". Might explain why I felt the deck levels had to be absurdly high to record normal audio. Can't wait to try a test.

The band has planned on providing me a feed from a separate mixer. Part of their pre-planning was... "Should we give him 'left' on channel 1 and 'right' on channel 2... OR can we give him 4 separate channels (#1 on ch1-L, #2 on ch1-R, #3 on ch2-L, and #4 on ch2-R)?" Their preference would be to split into 4 because they can separate more instruments and vocals, but Glenn's point about audio quality is of concern. I suspect that I'm better off counseling them to plan on 2 channels... Ch1 = Left, Ch2 = Right.

No kidding... you all are the best. Thank you for your advice, recommedations and input!
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Old June 5th, 2005, 02:46 PM   #8
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Quote:
Originally Posted by Joe Peifer
Amazing. I can't tell you how impressed (and happy) I am with everyone's feedback.

Jay, I had NO idea that the level setting of the front jack could effect the levels on the rear jacks. I just checked the camera and found the front wheel at "2". Might explain why I felt the deck levels had to be absurdly high to record normal audio. Can't wait to try a test.

The band has planned on providing me a feed from a separate mixer. Part of their pre-planning was... "Should we give him 'left' on channel 1 and 'right' on channel 2... OR can we give him 4 separate channels (#1 on ch1-L, #2 on ch1-R, #3 on ch2-L, and #4 on ch2-R)?" Their preference would be to split into 4 because they can separate more instruments and vocals, but Glenn's point about audio quality is of concern. I suspect that I'm better off counseling them to plan on 2 channels... Ch1 = Left, Ch2 = Right.

No kidding... you all are the best. Thank you for your advice, recommedations and input!
Just thinking out loud here, how about renting a multi-track digital audio recorder like those by Edirol or Fostex to capture the audio from the band's preferred multitrack feed, OR use a laptop with a multitrack audio interface to record direct to hard disc? You would also record a guide track on your DV tape using the on-camera mike during the shoot and use it to line up the video and audio up when you're in post, throwing the scratch track away in the final edit. Trying double system with a common analog audio recorder wouldn't work well but if you record the audio digitally you shouldn't have problems establishing and maintaining synch in post even though audio and video are recorded separately. Another advantage of such an approach is that you'll have all 4 or even more tracks of the separate instruments and vocals from the band and can remix them at leisure in post to give you the best sound - the mix for the final video might be quite different from one that sounds best for a live performance. That would give you more flexibility in the shoot as well since you could stop tape in the camera to select another shot while the audio recorder continues to roll and not lose the audio during the gap in video.
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