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View Full Version : Issues with our Sanyo PLC-XF35N Projector



blazer003
01-14-2008, 06:39 PM
I am trying to figure out the path of least latency and how to improve that path.

Here are the tests that I have done.

Output to CRT TV via composite - 2.5 frames of delay
Output to CRT TV via component (using only the Y channel) - 2.5 frames
Output to a LCD monitor via VGA - 5 frames
Output to our Sanyo PLC-XF35N Projectors via component - 7 frames
Output to our PLC-XF35N Projectors via VGA - 5.5 frames

We are a church trying to do IMAG and yet our delay is too great. If we can get it to 4 frames of delay, we can show it. That is our target.

My test straight from the composite to the CRT TV tells me the VT system itself is causing 3 frames from an un genlocked camera. That's what we'd expect. So far so good.

Straight to an LCD monitor using VGA is 5 frames. So I'm getting 2 extra frames of delay out of my video card which is a GForce 7600GS. Not quite acceptable latency.

Now, if I run component to my projector (which I know the component signal has only 3 frames from my other tests) whith no DAs or any other processing in between, I still pick up 4 extra frames of delay in projector processing, hence the 7 frames of latency.

If I run the VGA to the projector, I only pick up .5-1 frame of added delay to make it 5.5-6, but added on top of the extra 2 I'm getting from my video card, still a no go.

So now I'm at an impasse. I can't go component because my projector takes to long to process it, and I can't go VGA because the video card is causing latency.

So, to ANYBODY doing IMAG, especially with these projectors:

How many frames of delay do you have?
What type of signal are you running?

To anyone using VGA video out for a live situation:
What graphics card are you using and how many frames of latency are you getting?

Many have said that they are getting 2 frames, some 3, others 4 in their live situations. My question is what projector are you using, and are you going out component or VGA?

I have talked to people that have these same projectors and they say their projectors work fine for IMAG. So what, exactly, am I doing wrong?

rbartlett
01-15-2008, 07:00 AM
I don't know all that much on this subject. But what I do know is that digital projection systems that are forced to use their scalers have a latency tax applied to them. Do check that the VT-VGA-output is going out with a resolution that is native to the projector or LCD FPD.

Can the VGA card be connected in either analog-VGA or DVI mode? Try DVI in case this is more immediately serialized over that of the D2A/DAC path.

I'm not sure if the VGA card is able to add frames of latency. I'd imagine that the VT(sw)+Windows+driver layer does this. So if VT(sw)+VT(hw) output is less delayed, then the general purpose nature of a PC architecture is getting in your way.

There is one thing that is worse than long latency across all displays. That is, different latencies across the displays.

(just in case it wasn't obvious, sw - software hw - hardware)

blazer003
01-15-2008, 10:56 AM
Thanks for your reply.

First of all, they are both DVI ports on the card and then I use a simple adapter to change to vga. However, my monitor is connected with DVI (when I was doing my tests) so it's not like there is anything there causing any delay.

Certainly it would seem that Windows and the drivers are causing the latency.

So my question is do people do this (VGA out)? I know I've seen people saying they have. If so, are they getting this added delay, and if not, what cards are they using?

mschwarzzz
03-27-2008, 09:05 PM
Blazer003,
Anybody respond to you in any way? I've got the same issue of about 5+ frames delay and have tried two different graphics cards for VGA output to our Eiki projectors. I'd also really like to know exact configurations of those that have been able to get sub-5 frame delays using VGA output.

NewTek got anything to add?

skyytv
04-05-2008, 06:54 AM
Can you please send me a private message. I would like to know more about IMAG and digital projection in churches. I'm planning on using VT5 for church...

blazer003
04-05-2008, 03:27 PM
The ultimate answer is no. We are actually going to have to possibly go away from VT and buy a hardware switcher because we can't get the extra delay from the graphics card to go away.

No one who is using VGA out (if there is anyone) ever provided me any information what so ever. Not even what graphics card they were using, so maybe nobody is using it because they all have this same problem?

I don't know. I'm frustrated with the whole thing. Again, this doesn't seem to directly be VT's fault.

VT seems to be running ok, but something, whether it's VT or the drivers or the card itself, is adding delay when VT is trying to get its signal out of my graphics card.

ACross
04-07-2008, 09:12 AM
Blazer,

Having done a good number of trade-shows ourselves I can feel your pain on this issue. Getting a low latency through a IMAG system is actually quite a bit more complicated than one would really like it to be. The first thing to be aware of is that pretty much all digital gear adds to the latency of the total system. As the world has gone digital (and cared more about non linear editing than live production), this has become an increasing problem for IMAG and similar systems. This said, the following are some general rules that we have found help :


Where it is possible, I would genlock your cameras to the TriCaster output. This is actually not very difficult assuming you have cameras that have this capability. Simply use a TriCaster composite output as the Genlock source and run it back to the cameras and play with the phase relationship to get the lowest possible latency. Doing this allows TriCaster to bypass the input time-base correctors and this gain a frame or so of latency. You will find that doing this allows you to get a 2 frame latency through the TriCaster.
If at all possible, try running to the projector with analog video simply because it takes a lot of the complex extra steps out of the process. This is of course not always possible, or even desirable but it is worth mentioning.
If you are using DVI or VGA output from the TriCaster, I would try to match the resolution that it runs with the native resolution of the projector. On some (but not all) projectors this allows the unit to avoid using the internal scaler and thus reduce latency.
Some, but not all projectors, actually have a special low latency mode which disables some features of the unit itself. When we are doing trade-shows we always ensure that this is enabled ... it makes the hanging of the projector slightly more complex because you loose some of the ability to position and scale the image but generally this helps a LOT with the latency.
Some cameras seem to have a number of features that actually add more latency than you would expect. For instance, image stabilization has (by definition) to add a field of latency and sometimes more than that, so ensure you disable anything that you can.


I hope that this helps and please do not hesitate to contact me if you have any further questions or comments.

Best regards,

Andrew Cross, Ph.D
Executive VP. of SW Engineering
NewTek, www.newtek.com

johnlacko
04-17-2008, 02:41 PM
5 - 10 - 15 frames.... ha we are getting 20 frames...but not really an issue with our IMAG setup. This is because our screens are located in a different area of the building (video cafe we call it) so we just use our audio DSP to delay the sound about 70 miliseconds to compensate and make video to audio. FYI - signal flow is 3 JVC GY-DV300 cams -> VT5 -> Edirol LVS-400 mixer -> Extron DVS 406 scalar/switcher -> FSR VGA 6 way splitter -> Extron VGA to Cat5 converter -> Cat5 -> Extron Cat5 to VGA converter -> Sanyo PLC-xf31N