Video Delay...

S

Shy Clyman

Freshman
Sep 28, 2012
29
0
0
New York, NY
I hope this is the right forum for this...
anyway. Im being brought in to engineer and oversee a large outdoor event. Soundwise Im not too worried. In the past they had problems with the delay times and delay hangs etc. But i have already straightened everything out with the rental co. The locations and deployment of the speakers arent ideal. but we are dealing with permits and a very tough city... my concern is that the system is being delayed for live music etc. In the past they have had problems with the video syncing up near the delay hangs (the farther away form the stage the worse it got) Im no video guy but that has to be bc the video wasnt delayed to outer screens? What can I do to make sure that this goes off without a hitch, i want this account :)

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Re: Video Delay...

What format will the video be?
How will it be transported to the screens?
What type of processing, switching, playback etc. is on the front end?
How deep is the area to be covered?
About how far out of sync did it appear to be?
I assume at the far delay systems the video was ahead of the audio.

Depending on the above answers to those questions the video screens at the stage
may already be lagging behind the audio and live action on the stage.
Video delay lines that can delay a video signal in the order of 1000's of milliseconds
cost big money.

Don't forget that the speed of sound is at a stand still compared to light. Depending on the distance
to be covered with the delay systems even if the audio and video is in perfect sync say in the front row
the further back you go the audio will get further behind the video.

Delaying the video may get the sync closer but it will only be in sync in one area for the audience.
 
Re: Video Delay...

Don't forget that the speed of sound is at a stand still compared to light. Depending on the distance
to be covered with the delay systems even if the audio and video is in perfect sync say in the front row
the further back you go the audio will get further behind the video.

Delaying the video may get the sync closer but it will only be in sync in one area for the audience.
Click to expand...

Read this over and over until you fully comprehend it. I had a client (they build advanced commercial aviation products, like airplanes and structural components thereof) who, in spite of masters degrees in engineering, failed to understand this.
 
Re: Video Delay...

Tim McCulloch said:
Read this over and over until you fully comprehend it. I had a client (they build advanced commercial aviation products, like airplanes and structural components thereof) who, in spite of masters degrees in engineering, failed to understand this.
Click to expand...

In addition to this being true, video is usually already delayed 100ms or more due to framebuffers and other monkeybusiness in the video chain, so it looks funny at the front of your area in the other direction with audio being way ahead of video.
 
Re: Video Delay...

TJ Cornish said:
In addition to this being true, video is usually already delayed 100ms or more due to framebuffers and other monkeybusiness in the video chain, so it looks funny at the front of your area in the other direction with audio being way ahead of video.
Click to expand...
Yeah, usually you need to delay the audio to line up with the video.

Generally, the audio can be lagging the video by a pretty good amount before things get screwy.

We are used to seeing this every day as we watch someone's lips move well before whatever they are saying actually makes it to our ears and then is processed into "hearing" by our meat computer.
 
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