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View Full Version : Extra Frames of Delay Out of VGA?



blazer003
01-15-2008, 07:49 PM
I have set up tests and have found that component out to a CRT Television screen via either component or composite has 3 frames of delay (video is delayed compared to live action in front of screen) with a non genlocked camera, which I believe is normal.

Because our projectors are native 1024x768 resolution (and going component is very laggy at 6 frames), I'd love to go live video out on one of our VGA ports, however I'm getting 5 frames of delay from VGA out to a regular CRT computer monitor and 5.5-6 (probably 5 frames and a field) on the projector.

That obviously means that an extra 2 frames are being added by some part of the process of the system getting the video to the graphics card. Whether it's the processing time on the card itself, or something with the drivers (which are up to date) I don't know.

I have a GeForce 7600 GS graphics card.

Anybody using VGA out for live IMAG? If so, how many frames are you behind from live action to screen? If it's 3 or under, what kind of card are you using?

I'm very willing to buy a new card, however I don't want to just keep buying until one works. Anything else anybody can think of that may be effecting the timing? And yes I have desktop manager turned off.

Oh, and if I go component directly to the projectors, there are 6 frames of delay total. The projector is adding 3 frames of delay to process and scale the image, so that's a no go. I need to get it down to 4 frames or less.

The projectors are Sanyo PLC-XF35N.

jsanfilippo
01-19-2008, 08:52 AM
I don't have an answer to your question, as I use component out to my Sanyo projectors, too, and haven't tried VGA out. But my projectors certainly do add some latency. I know my VT is running tight... genlocked cameras.... everything seems good there.

I was wondering about using a high end scaler external to the projectors and Newtek.... running the component up to the projectors but having a scaler up there just before the projectors. But I don't know if I'll get any less delay using a dedicated scaler. Anyone tried it?

But as a next step, i'll try running VGA out from my VT and see if that's better.

What was your process for measuring... so we can talk the same language.

Cineman
01-19-2008, 11:30 AM
Jamie,

I honestly think that your friend Jef, Pizazz has done the most study and has the most knowledge on high end dedicated scalars. Eons ago we were gonna spend some time together visiting booths and researching this together at NAB until I got sidetracked. He has gone much further than that today.

Guess it is common knowledge now that for lowest latency using VGA out to the projectors, is to have the VT computer set to the projectors native resolution?

I predict that you will have slightly more latency sending VGA output from the VT. Since it depends so much on your VT's computer and projector specs, my own tests wouldn't apply for you folks.

Nes Gurley

bob anderson
01-19-2008, 11:52 PM
Usually, the "extra delay" you mention is an issue with the projector. Projectors often have native 2 to 10 frame delays. (They are "designed" for your home theater, where that's not too bad)

But there's more to the equation. Every un-synced input you plug into your VT ads to the delay of the final output. (The VT has to internally sync all the inputs) I've seen delays, from the VT and the projector adding up to 15 frames making the projector output pretty unusable.

So.. consider a frame sync/TBC to remove this "part" of the delay issue for your inputs. (Anyone remember those DPS TBC 3's you sold for $100?) Also.. run the projector out in the projectors native resolution. If the cable run from the VT to the projector is over 50 Feet, consider an active cable solution, which is basically a DVI cable with a line driver built in.

I managed to get that 15 frame delay down to a "tolerable" 6 frames.

By the way.... In the NewTek trade show main stage... they use a digital delay on the house PA to match the delay in the VT.. A smart solution.

Bob Anderson

PIZAZZ
01-20-2008, 09:02 AM
By the way.... In the NewTek trade show main stage... they use a digital delay on the house PA to match the delay in the VT.. A smart solution.



uh. While an audio delay can work in really large rooms to sync things up, in a tradeshow environment it would be too disorienting to the talent. I am not sure what tradeshow you are referring to but at Siggraph there was no audio delay in use. I know because I did the AV for the booth as I am also for NAB in a few months.

PIZAZZ
01-20-2008, 09:07 AM
I was wondering about using a high end scaler external to the projectors and Newtek.... running the component up to the projectors but having a scaler up there just before the projectors. But I don't know if I'll get any less delay using a dedicated scaler. Anyone tried it?.

Yep tried it. Yep bad idea. The scaler adds even more latency to the output.




But as a next step, i'll try running VGA out from my VT and see if that's better.

Definitely give that a shot if you can Jamie, Try not to go through an active DA if you can to see if there is a real difference. Go straight out of the VT with the second or in your case 3rd/4th head. Set the resolution on that output head to the native resolution of the projector which I believe in your case is 1024x768.

Let us know how you come out.

jsanfilippo
01-20-2008, 09:11 AM
I've come to accept the latency I have here, because it's not too bad (which is why i haven't done anything about it recently)... but reducing it a few frames would be nice. it's definately a few frames less on a CRT monitor when compared with the projector output.

i'll try using the VGA out, since I have output #4 free and will report back. i'm wondering why i haven't tried before... i think all the cabling is there already. there's no difference between VGA program out and Video program out, is there?

PIZAZZ
01-20-2008, 09:20 AM
there's no difference between VGA program out and Video program out, is there?

There is actually... VGA Program out in use allows you to key an IVGA input directly over the top of it. Kinda sorta giving you a 2nd DSK layer. This is much better implemented in VT5 with the capability to fade in the IVGA.

BTW when are you ready to update to 5. The waters fine come on in. :)

Cineman
01-20-2008, 09:41 AM
there's no difference between VGA program out and Video program out, is there?
Think that this is not what you are really asking, but that answer will be in it. VGA program out is what you see on the VT interface VT Vision for Program Out. Video program out would be as you would see it on an NTSC Program Out Master Monitor. The differences would be as seen on comparing these two.

Of course there are adjustments for your projector, so it could be changed there. Should be able to make a latency comparative test before any need to do that.

Nes Gurley