Live worship recording - Delay problems at DVinfo.net

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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 April 6th, 2009, 03:57 AM   #1
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Live worship recording - Delay problems

Hi everyone!

Our church has just set up a new building with 3 XHG1's and 1 XLH1 connected via HD-SDI and Genlock feeding through a broadcast pix switchboard then back out to HD 1080p projectors. This all looks great.. however there is a definite frame delay getting back to the projectors.. and this just isn't cutting it. We purchased the cameras because of the Genlock feature to prevent this lag in video but it is happening anyway..?

For our music portion of the service the clap is very noticeable. If the cameras are causing the problems then I am afraid we'll have to get rid of them :(

Any feedback is greatly appreciated.
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Old April 6th, 2009, 08:15 AM   #2
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Hi Michael,

You don't need to get rid of the camera, what you need are seamless switchers (Extron 408) to switch seamlessly & get rid of the delay. They are quite expensive but it does the work, you can switch from PC/Camera/DVd without the delay. You can ask a local AV Company for a demo.

my 2 cents
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Old April 6th, 2009, 01:07 PM   #3
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here is the switcher we are using:

Broadcast Pix Slate 1000Ghd

I know nothing about switchers.. I'm a DP/Camera Op.. so broadcast is new to me.

I do know the switcher wasn't cheap.. (at least in my opinion.. $30K); and so far does a great job.. we are just trying to fix the delay in the system.
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Old April 6th, 2009, 01:10 PM   #4
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sorry I think its 100 (not 1000)

here's a link: Roscor Corporation - Roscor Direct
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Old April 6th, 2009, 02:32 PM   #5
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There are always delays whenever you go from analgue to digital and back again. The switcher claims a single frame delay, but there's also the delay coming out of the camera and the delay going back to analogue for the projectors. Genlock in itself, doesn;t get rid of delays - but having genlocked sources means the switcher doesn't have to re-synchronise them. The Panasonic MX-50 was really popular as it could sync non-genlockable sources, but most people could spot the delay. It only takes a few frames of delay going through the total system to be visible. 5 frames is quite obvious and many people can spot less than this.

I've had a search around and cannot find the specification of these cameras dealing with any frame delays - so I guess the only solution is to try another camera and see if the delay gets better? Best of luck.
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Old April 10th, 2009, 10:55 AM   #6
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I remember reading somewhere that Canon XH- and XL-series have one frame delay on SDI output. I'm not 100% sure of this, as I have no personal experience, but searching the web with keywords like "canon xl h1 sdi delay" gives a few hundred results.

As far as I know, Genlock does help a bit, but no more than one frame. Frame based video mixers without Genlock (usually cheap) needs to receive a full frame from camera before it can sync the sources, because cameras might be drawing frames with different timing. With Genlock, the mixer itself gives sync signal to cameras and as the sources are synced, there is no need to use frame based synchronization. This is pretty much the same that Paul said above. In your system the cameras seems to be already Genlocked.

One professional told me that many low-delay live production systems are based on following:
1. Video output on cameras is analog and Genlocked
2. Usage of analog video SWITCHER, not even a mixer, but a simple switcher, that just changes the the source with practically no delay.
3. Video projectors with little processing as possible (no scaling etc.)

I'm pretty sure that modern digital system can have almost identical results, but I think you need to put a serious load of $$$s to achieve such low delay.

I've used a low-budget live production system which contains (briefly) Sony PD-150's, Datavideo's mixer, Extron's scaler and matrix switcher and Christie's projectors. The delay is about 4-5 frames, which can be quite easily spotted, especially when shooting music events. In this system, the worst link seems to be Datavideo's video mixer (SE-500).
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Old April 10th, 2009, 12:17 PM   #7
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Michael,

Have you tried feeding the camera directly to the projector (bypassing the switcher) to see how bad the delay is? This would tell you whether it is the camera or the switcher adding the delay.

How is the output of the switcher getting to the 1080p projector? Is the switcher outputting HD-SDI (1080i) which your are upscaling to 1080p? This could also be the source of some delay.
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