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Author Topic: Calculate Video Delay  (Read 3115 times)

Bernard connolly

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Calculate Video Delay
« on: June 02, 2009, 05:46:22 am »

Hi
Wondering if anyone has a tool or software they can recommed to calculate the delay betwwen audio and video on and istalled system. We installed a system and there is a lip sync problem. Another supplier install LCD screens and the response time is really bad. Need to workout the delay and see if we can delay the audio enough to create a working resolution.

Thanks for your help.
Bernard

Ken Freeman

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Re: Calculate Video Delay
« Reply #1 on: June 02, 2009, 11:02:57 am »

Do you want to calculate the delay or measure it?

Ken
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Bernard connolly

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Re: Calculate Video Delay
« Reply #2 on: June 02, 2009, 11:07:34 am »

Well spotted Ken English failed me. I want to measure it.

Mac Kerr

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Re: Correct Video Delay
« Reply #3 on: June 02, 2009, 12:39:42 pm »

Do you want to measure it or fix it? Why not just add delay to the audio 1 frame at a time till the lip sync is OK? figure a frame for each digital video device to start. A video frame is 33ms, so start with 66ms and go up in about 33ms jumps. It's pretty easy to do.

There is a device to measure the lip sync, but my experience has shown it to be kinda flakey. Unfortunately I can't find info on it. It would output an audio and video pulse and then time the audio pulse to the video pulse on the screen. It gave you the offset in frames. As I said, it wasn't very consistent. Doing it by eye is faster and just as accurate.

Mac
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Karl P(eterson)

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Re: Calculate Video Delay
« Reply #4 on: June 02, 2009, 02:16:05 pm »

If I had to guess this is for live application and he is wondering if the delay needed to match the video and audio together would result in an unrealistic delay time for a "live" show, or rather one in which people can hear this delayed audio while looking at the people on stage.

If this is truly the situation the correct answer would be to replace the video cameras/switchers/scalars with a timed system to eliminate as many delays as possible and use a low latency down converter to drive the screens at their native resolution. You will also want to put the screens into "game" mode, or turn the internal scalars off, if there is such an option.

Karl P
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Bernard connolly

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Re: Calculate Video Delay
« Reply #5 on: June 03, 2009, 03:22:46 am »

Thanks guys. Yes its a live application so I cant really delay the audio by much as the on stage act usually bands will hear it and the venue isnt big enough to pump on stage monitors hard.

The whole system is run component and since we didnt supply the screens I think this may be the problem. I have check with the switcher tech guys and they tell me in to out is slightly less than 2 fields, so its not that.

Could the cameras ( again not ours) add delay they are Canon xh g1 half domestic I think. Like the idea of switching to game mode on screens, is the latency less?

The joys of coming into the loop on a job already half done!!!!

Again thanks for coments and thoughts. I suppose I am hoping I missed something simple. Should have included service contract.

Brad Weber

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Re: Calculate Video Delay
« Reply #6 on: June 03, 2009, 08:25:46 am »

Since you are running analog component video there will probably be some latency in the camera converting to that, some in the switcher, some in the projector scaling and possibly some in any other signal processing.  Each by itself may not be a problem but the aggregate of all of them may be.  So while the switcher may be only two fields or one frame, that is added to any other latency.

I believe that Karl was referring to the 'game' mode or turning off the projector's internal scaler being in conjunction with using an external scaler, you still have to have something scaling the component video to the projector's native resolution.
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Brad Weber
muse Audio Video
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