11/21/2005 1:22:21 PM

I worked at a conference this summer and used my Sony HC-1000 digital video camera with song show plus. I used firewire in on my laptop that has well enough power to suppor that type of work. But I still have lag between real time and the video. The video on screen is not cued with real time. What do I do?

11/21/2005 2:38:11 PM

As I understand it, there will always be some lag. Fire wire and PCs just aren't fast enough.

I believe that if you really want to do an IMAG implementation, you will need some sort of video mixer to do that, instead, using chroma keying and lower thirds and all that kinda good stuff.

Hopefully a real expert will chime in here. I don't even play an expert on TV.

11/21/2005 3:25:42 PM

Osborn is right.  Anytime you run a live video device through a PC you'll get some sort of lag.  This is because the video feed is software processed instead of hardware processed. 

IMAG devices (video switchers etc) process the video feed through hardware.  They can do this because they're a high end dedicated device that doesn't do anything else.  Because computer hardware is sort of a "all in one" kind of approach they lack the dedicated hardware. 

11/22/2005 6:25:08 AM

So can a imag device be configured to work with SSP? I'm new to SSP, but I'm thinking it would probably just mix the video out of the computer with video out of the camera and mix them in the imag device. If you were using that then I guess you would only use text from SSP?

Am I even close?

Thanks,
Alton

11/22/2005 8:54:38 AM

11/22/2005 9:24:20 AM

Keep in mind that I have very limited third hand knowledge, but this is what I've heard.

You can use some sort of video mixer to combine the output of the SSP computer with the camera(s). You need to set a solid background for SSP and then, with the mixer (I think that's the device), you "chroma key" that color out, so just the words appear and the background goes away, showing the live video behind it.

You may want to do some searches and perhaps ask the question over at http://www.churchmedia.net

Like this thread for instance:
http://www.churchmedia.net/community/forum/showthread.php?t=6677

11/23/2005 12:46:37 AM

We use SSP in an IMAG set up for many of the same features as alot of user do. Text over video is easily accomplished using SSP and a video switcher. Basically you use a DSK (down stream key) with the text as your source and "key" out the background color. You can also use a crop function with the DSK. With a adequately featured switcher you can also do a color key and use transitions to fly in your text using hundreds of transitions. We use a Sony DSF-700, it's a 8 channel switcher w/ 2 SSP machines feeding it graphical content. It also allows for animated lower 3rd titles through SSP as well as basic text over video with no lag. To set up a SSP machine to a video switcher you will need a scan converter to scale the computer resolution to video resolution. Hope this helps

11/23/2005 5:17:06 AM

We have a Sony camera whose output signal is composite video, fed to the projection computer through a composite-to-firewire converter. We've used it only with SSP.

I have used the video as background to a SSP countdown, and as live video (IMAG) using SSP's Live Video pro-module (I wonder whether the old version still works with the beta). There is no apparent lag, it works fine. We don't use it for services (auditorium is too small), only occasionally for special circumstances. Notice we do this limited IMAG without external video equipment.

The situation, I suppose, where we would need a switch (mixer) would be to seamlessly switch between several cameras.

11/29/2005 9:35:49 AM

I played with the old live video and it still works with the beta.

11/30/2005 3:48:14 AM

WOW!!!!!! You must have a pretty Hi-spec computer!!!??? When I have tried it, not only is there lag, but the output video seems to also have a very low frame rate. I can't wait until there is computer hardware (or whatever is needed) out there, so that most computers can display live video to a high enough standard, through programs like SSP. It would make the list of equipment a lot shorter!
Besides, at the moment, the only way I know of to MIX between Computer video signals (VGA, XGA, etc.) and video signals (from cameras and the like) at Computer video signal resolution, is with the Sony AWS-G500 which cost a LOT of money.

11/30/2005 10:16:30 AM

I'm sure it seams easier to just run everything through SSP but to have a professionsal presentation video lag just doesn't work. To spend the money to make your computer faster to try to handle live video better you you could be many steps ahead to a video switcher that would solve the lag problem. Even an inexpensive switcher is better than a lagging image. My .02

12/8/2005 7:28:18 AM

I doubt we have more than a few frames lag using a standard current computer (DV camcorders likely will impose additional lag and processing requirements). Since you have a frame-rate problem there are likely issues other than computer speed to consider.

For instance, if you have a media-capable computer you should be able to display TV on your computer. An ATI All-In-Wonder card claimed 120fps on only a 500MHz computer. Therefore, if your camera can provide the same signal required by the ATI AIW, it seems to me you should be able to get a full 30fps with little difficulty.

12/9/2005 3:56:56 AM

Well, I just had a play with a video camera hooked up to the S-video in on the capture card on my church's media computer. I was actually quite impressed with it. There was only a few frames lag, much better than when I used firewire.
It wasn't too jerky either. I suspect if you have different refresh rates on the projector and the input video signal, there will be problems. The trouble is, because I live in a PAL country (50Hz), I cannot seem to match the projector and input video signal refresh rates (projector can't seem to do 50Hz).

12/16/2005 2:28:42 PM

At the risk of "beating a dead horse", I did some simple arithmetic regarding the so-called IMAG "lag" problem. The problem can certainly be real under some circumstances but may not be something so certain or severe as to dread and avoid entirely.

The arithmetic is rather simple. Sound propagates at roughly 1130 feet/second (off-shore people will have to do their own conversion to meters) and video is at 30 frames/second (again, PAL is different, as is film).

That gives you 33 milliseconds per NTSC frame and 37 plus feet per frame.

During IMAG projection time, assume the audio is live and your system incurs 1 frame of video processing lag. That would mean that viewers 37 feet from the screen will see the video perfectly in sync with the audio - while those sitting at a computer monitor (0 feet) will have a 1 frame lag. Those sitting 75 feet back will encounter a 1 frame audio lag behind the video (because it takes two frames of video for the audio to get there), which actually is almost unnoticeable.

For other frames of lag and other distances from the screen, just perform your own arithmetic.

Did I do this right?

12/16/2005 4:53:49 PM

I'm not going to argue the math because I don't know, but it seems that you forgot to account for sound ammplification systems like microphones and speakers.  The church I grew up in had speakers every 20 feet or so which means that I was never more than a few feet from my relative source of sound.

Besides, I doubt most people would really notice a 33 millisecond delay. 

12/17/2005 12:00:22 AM

BTW, our church has an FSR Compass switcher, a $5000 piece of equipment --  and guess what -- it has a video lag as well -- certainly as much as the computer has.

12/17/2005 12:40:06 AM

Alot of the newer switching equipment that scales scans etc. all have various amounts of lag. especially when they start plugging this one into that one for various distribution.

I have been involved in Large Gig's where the FOH sound has been delayed to allow for the "imag" Lag..

I guess it all comes back to processing..

Rod

12/17/2005 12:40:59 AM

Remind me never to buy one of them then!

12/17/2005 12:50:40 AM

Genlock will fix some of your hardware lag issues (if you have no budget!)

12/17/2005 12:51:44 AM

Sorry, way off topic there.

12/17/2005 1:08:07 AM

The only problem I can see, with running everything to the projector at video resolution, is when you want to display full screen computer graphics (like PPT's etc.). From my experience, computer graphics, scaled to video resolution, look terrible on a big screen. It might just be our scaler though. Has anyone displayed PPT's satisfacturily as NTSC/PAL standard video, on their projector? How noticable is the difference between displaying as NTSC/PAL and VGA?

12/17/2005 7:16:42 AM

That stinks!  We have a MX Pro mixer we use with video cameras and it has no lag, it works great.  Our camera guy uses 3 cameras and they go through a Sony or Panasonic switcher that costs about $5000 at least and then they take that feed and feed it to our MX Pro Mixer and seriously we don't have any lag.  Our cameras are very high end also.  We only use live feeds during special times of the year though like the Christmas season. 

12/19/2005 7:22:01 AM

OK, in summary my conclusion from all the replies would be that one can't simply blame SSP or PCs as being the cause of a terrible "video lag" and that therefore one should avoid using PC IMAG at all costs.

The so-called lag issue gets complicated for many reasons, not the least is raw sound itself. Sound installation people are concerned about reflections off of walls causing sound to arrive at someones ears from different directions, one delayed from the other by maybe 10 MS. Or we buy signal processors to interject 30MS delays into sound intentionally to enhance vocalists. Or we buy home/auto audio systems that allow choosing the amount of lag (you've seen them, selecting stereo, hall, chamber, whatever-name-they-use to add various kinds of echo to your sound). We deal with a seemingly infinite variety of reverberations and angles, attentuation, and resonant frequency issues. The point being that we work all of these "lag" issues completely apart from a computer or video.

Of course, sync'ing sound to lip motions is a bit more rigid. You might not be able to live with 15 frames of lag but you might find a few frames to be fine. In addition consider there are many IMAG situations that are not focused on closeups of someones mouth/audio.

So go ahead, give it a try, don't be afraid of even trying certain kinds of IMAG. Use it where it works and don't use it where it doesn't work.

12/19/2005 7:28:18 AM

Well, yes, and that is why the experts typically advise to send VGA to the projector and leave the other modes of the projector unused. And why you want to set the VGA to the projector to be at the so-called native resolution of the projector, so that not even the projectors built-in scaler gets invoked.

12/19/2005 7:33:55 AM

You have probably noticed most installations employ speaker clusters. This is usually considered preferable to the other problems caused by distributed speakers.

12/20/2005 3:30:01 AM

The reason I asked those questions, is because if you run everything through a video mixer, whose output goes to the projector, everything will have to go to the projector at video resolution.

12/20/2005 4:42:24 AM

Or put a scaler after the Video mixer and upscale to VGA again...

Rod

12/20/2005 5:28:13 AM

I mean this in the nicest way possible: As far as I can tell, there is not really any point doing that in regards to resolution. Once you have brought the VGA down to video resolution, it's going to stay that quality. To get down to video resolution pixels have to be combined, there is no way of getting them back again.
A good example of this theory is in microsoft paint. If you "stretch" an image to say 20% (like scaling to video resolution), then "stretch" it to 500% (like scaling back to VGA resolution) you will rarely end up with the same quality image you started with.

Having said all of that. There are other issues to take into consideration other than just resolution. But it still seems to me that if VGA is brought down to a video standard, it will always basically be the quality of that standard from then on.

12/20/2005 6:27:08 AM

I agree.. I always want to keep everything to it's "Best" resolution.  I would much rather use a scaler to bring the video up to the computer (VGA) than take it down (to Composite). Unless its for things like stage monitors, then we are talking a whole new ball game though..

In terms of final Output. Adding the scaler to bring the signal back to VGA will help in one way, and this depends on the quality of the Scaler built into the projector. But by using a "Good Quality" scaler to bring the video back to VGA the projector can at least diplay it in its native resolution. This could be alot better quality than using the inbuilt scaler inside the projector to do this. ( some of them even add quite a bit of Lag to the pictures while processing and scaling )

Agreeing that it will not bring back lost resolution. It will however allow the projector to display what it gets as good as possible and in some cases with considerable more light output.

Just my thoughts
Rod

12/21/2005 9:56:38 AM

A couple of years ago we did some extensive testing along these lines. One test was to send the output from a comsumer VHS player to the projector via two cables: VGA and composite video. The VHS output went through a composite amplifier first; one amplifier port went to a scaler and on to the projector as VGA, another went to the projector's video input. We had to switch the projector back and forth so the test team saw only one picture at a time (rather than both versions side-by-side).

It was universally agreed that the up-scaled VHS picture looked "twice" as good as the plain composite picture (whatever twice means).

But notice we did not test beginning with a digital device (i.e., perhaps a computer from an appropriate test file), scan converting down, then scaling back up. In this case I would predict just what has been mentioned in previous posts; the up-scaled VGA would have lost something from the original VGA.