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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old May 6th, 2008, 10:21 AM   #1
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Accuracy of XH G1 audio levels?

Hello,

I've been having a bit of an ongoing problem.

When I send tone from a Sound Devices 302 mixer to the camera set to receive line level, I am able to fully open the camera's audio levels and get the reading of -20 dB as is supposed to happen. Now I have 0db on the mixer matched to -20 on the camera. Problem is, with every test I do with real human voices, 0dB on the mixer corresponds to -12 db not -20. Something funny is happening here.

I've also tried connecting mixer to camera at mic level. Here again I am to set the camera pots to mixer tone such that 0dB tone on the mixer Vu equals -20 on the camera. When I do this the same phenomena occurs. In real life situations 0Db on the meter equals -12 on the camera not -20.

I've been trying for days to figure this one out. I'm now beginning to wonder if the anomaly isn't occurring somewhere in the camera for I've noticed something when setting the mixer to camera at mic level. In order to set the camera's two channel levels to -20 to match the 0dB tone coming from the mixer I have to place the camera's audio levels at different points. One channel is 4/9 open the other 2/9. That doesn't make sense.

Guess my question is: How reliable and accurate are the camera's audio levels? When the mixer says 0dB and the camera is saying -12, rather than -20 as it should, is the camera reading correctly?

Thanks.

John
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Old May 10th, 2008, 06:07 AM   #2
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Quote:
How reliable and accurate are the camera's audio levels?
Maybe the issue is peak vs average reading meters,

Accuracy will vary from camcorder to camcorder (due to normal manufacturing tolerances) and due the users ability to interpolate pot settings and what that the A1 meter is really saying given that the display is discrete segments, not like an analog meter where you can readily interpolate between marks.

That said, I will check my A1 later today and report results.

.
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Old May 10th, 2008, 08:05 AM   #3
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Dear John,

The Sound Devices 302 puts out a sine wave as the "Tone" signal. This is the same as for most all mixers.

A sine wave peaks and average will read the same on the Canon XH A1, as it will for most all cameras. The peak energy and the average energy is the same.

So the reading of -20 for the peak and average reading is correct.

For the human voice, the peaks and average readings will be different.

It is not unexpected that the peaks may go to -12 while the average is less than that.

Summary: Everything appears normal.
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Old May 10th, 2008, 12:41 PM   #4
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In summary, the XH-A1 meters appear to be reasonably accurate, and channel balance is good for line input signals at the XLR input jack.

In a quick test: When the XH-A1 is set to XLR, line input, and a nominal 50 ohm, 0 dBM source (actual measured generator signal outout at 1 kHz was 0.847 volts output at no load ) is connected to the XH-A1 XLR input.

With the level pots set to max, the XH-A1 meters read -20 dB, and the signal output to firewire capture was -19.5 dB below the digital maximum sine wave record level. It is the same for each channel. Average noise level in the channel with no input was about -86 dB below max digital record level.

With the level pots set to about half scale (by uncalibrated eye ball), the signal recorded on one channel was -38.0 dB below max record level and the other channel was, -36.5. (This 1.5 dB difference could be my eyeball.) If I used the CH1-CH2 setting (where in the channel 1 XLR input was recorded to both channels, the firewire output was -38.0 dB for both channels. Average noise in the unrecorded channel was about non existant (plus/minus one sample from zero).

At this pot level (-38 dB record level), only one tick mark was lit on the meter, so setting levels by meter this low a level is not a precise operation, much as setting levels at -20 VU on an analog meter is not.
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Old May 10th, 2008, 11:36 PM   #5
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can the A1 level show red when its peaking like the DVX?
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Old May 11th, 2008, 03:25 AM   #6
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Originally Posted by Kiflom Bahta View Post
can the A1 level show red when its peaking like the DVX?
Yes, the last segment on the meter is red.
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Old May 11th, 2008, 08:05 PM   #7
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I don't know what am i doing wrong but my A1 doesn't show red when it is peaking everything is white but my dvx does. Do i have to turn it on somewhere?
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