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Author Topic: video with audio capture system reality check  (Read 1639 times)

Tom Young

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video with audio capture system reality check
« on: November 05, 2013, 11:01:22 am »

I'm a seasoned live audio guy who installs the occasional video capture system in HOW projects. Due mostly to lack of documentation and then/also my base ignorance, I need help mentally sorting out what is going on in a system I have installed.

The system consists of a PTZ camera feeding (2) DVR's (plus camera controller and video monitor). I am also feeding a stereo audio mix from the FOH mixer to the stereo inputs of the 1st DVR. The 2nd DVR is for when the event goes over the disk record time limit OR if the 1st deck fails.

As installed, the system is wired like this: composite video (from camera) and stereo audio connect to inputs on the top DVR ("primary"). Composite video and stereo audio outputs (of top deck) connect to inputs of bottom DVR ("backup"). Then, composite video and stereo audio outputs of this 2nd DVR feed the inputs on the video monitor. See block diagram.

This system works. But I don't know how the signals are handled within the DVR's. So the questions are:

1. when in non-record mode I can see the video signal on the monitor and hear the audio through the video monitor speakers. This indicates that the audio I am hearing comes from the DVR's inputs (no digital conversion). Right ?

2. when the primary DVR is recording, I suspect I am monitoring its outputs of that deck via the inputs of the backup deck. Right ?

3. If answer to #2 is yes, the signal has gone through input (analog to digital) and output (digital to analog) processing/conversion. Right ?
 
4. video and audio appear to be synced when viewed. Is the A/D and D/A conversion the same for video as it is for audio ? If not, what are the two different conversion rates ?

Thanks for any help on this-
« Last Edit: November 05, 2013, 11:57:12 am by Tom Young »
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Tom Young
Electroacoustic Design Services
Oxford CT
203-888-6217

Erik Jerde

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Re: video with audio capture system reality check
« Reply #1 on: February 10, 2014, 10:04:03 am »

Hey Tom, hard to answer all your questions without knowing the dvr models and probably doing actual measurements.  I would recommend you make a slight change and just use a DA to split your input signal and feed the dvrs and monitor separately.  Right now it looks needlessly complicated and the chaining of devices is worrysome.

Just looked at the date of your post, you're probably past the issue now but if not I hope this helps.
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