vtc, h.239 tandberg-polycom (newbie) [Archive] - VTCTalk.com

ryness

11-10-2005, 09:09 PM

I'm a relatively newbie to VTC, altho not to a/v engineering and computers. I'm hoping this forum can help me get some wrinkles smoothed out in our VTC setup.

We're conferencing with sites and everything is fine until we go to show the contents of the laptop's desktop (powerpoint, or webpage, or whatever). Small text is just unreadable at the far site.

We've got a Tandberg "Educator" system which consists of a 6000 codec and presenter/ePac module. I've enabled the h.239 setting in the codec's config.

Most of our remote sites are using Polycom vsx* models with the "visual concert" box.

My questions:

1) to achieve ideal quality for displaying non-NTSC signal, do I also need a scan converter box to put between my laptop and the Tandberg 6000, or is that builtin to the 6000?

2) subjectively, is h.239 good enough to display the text on web-pages, or should we just use something like Elluminate or VNC's java web-viewer and not even bother trying to show that kind of content over VTC?

3) on the PolyCom side, if they have the "visual concert", do they need to enable it in anyway or is it just on and active if its plugged into their signal-path?

trapehzoid

11-10-2005, 10:34 PM

1) to achieve ideal quality for displaying non-NTSC signal, do I also need a scan converter box to put between my laptop and the Tandberg 6000, or is that builtin to the 6000?

You should be using the VGA input of the system.. that will give you the best possible quality. No extra gear required there

2) subjectively, is h.239 good enough to display the text on web-pages, or should we just use something like Elluminate or VNC's java web-viewer and not even bother trying to show that kind of content over VTC?

h.239 is the transport.. what's important is the transmitted resolution and displays being used. both the tandberg and polycom vsx can do XGA quality nativly. This means you can send basically what you have on the laptop without much degradation to the far end. However, to get that quality, you still must put it on a display that can make the most of that resolution. The units will scale a high res image down to display on whatever output being used. So if you take an XGA image, and try to display on a NTSC TV screen, it will be poor. Hook the display up to something that can display the image at full resolution, like a monitor, projector, or plasma and the image will look nearly as good as the original image. The second part of that to remember is.. and has nothing to do with H.239 is.. how big is your image compared to the distance its being viewed from. VTC doesn't change any of the rules there. You can't expect something 1/2" tall to be readable 20ft away. Make sure your displays are sized for the content and where the audience is relative to the screens.

3) on the PolyCom side, if they have the "visual concert", do they need to enable it in anyway or is it just on and active if its plugged into their signal-path?

Its pretty straight forward once you plug it into the vsx. My guess if you are having quality issues are they are using the regular S-Video or Composite outputs of the VSX, and not the XGA output of the VSX to display their graphics. This is configurable in the unit, based of course on how you have your displays hooked up.

Using H.239 is the way to go, as long as you have some sort of display technology in place to make the most of your PC content. Using something like VNC would be a major pain for people trying to use the system. The only alternative I would offer would be something like web-conferencing.. which has its advantages if people each have their own PC to use in the conference. Otherwise, H.239 is best because its really plug and go.. no extra steps or software required.

Check out what the VSX systems are using for their display setup.