Problem getting laptop's video signal accepted

[djcmackay]

Hello all, I'm new to the group. I'm trying to increase the amount of videoconferencing happening at my University, and while testing the systems we have got here, I've run up against a minor problem.

When I connect the SVGA output (1000x800) of a linux laptop to our Tandberg systems, the Tandberg says something along the lines "invalid video signal" - even though the same signal, if fed to any SVGA projector, displays just fine.

I'd like to understand (a) what is it about a Tandberg that is different from an SVGA projector - so that we have some ideas of what to do to the linux laptop to fix the problem; or (b) if anyone has a solution, that would be brilliant!

Thanks very much,
David (djcm1@cam.ac.uk)

[djcmackay]

By the way, to be precise, I checked what output the laptop is sending, and it is 1024x768@60 (using a piece of software called i855crt).

i855crt swcursor on 1024x768@60

[Sean Lessman]

By the way, to be precise, I checked what output the laptop is sending, and it is 1024x768@60 (using a piece of software called i855crt).

i855crt swcursor on 1024x768@60

Which is it? SVGA or XGA?

If you are sending 1000x800 (whatever that is), the TANDBERG does not support that as an input resolution. A list of the input resolutions and refresh rates supported can be found in the manual.

Sean

[djcmackay]

Which is it? SVGA or XGA?

If you are sending 1000x800 (whatever that is), the TANDBERG does not support that as an input resolution. A list of the input resolutions and refresh rates supported can be found in the manual.

Sean

Sorry for the imprecision:
I'm sending 1024x768 at 60Hz from a standard PC VGA output.
i.e., a completely standard laptop PC output.

[Tallman2]

Hey dj
Are yo sure your refresh rate is set for 60hz?? I have seen all to often that this is a problem. If it is??? It should work try droppnin down to 800x600 to see if that works.

[helix-2000]

Are you running PVX from laptop? If not what application are you using for video?

[djcmackay]

Thanks for the feedback! I will try dropping resolution to 800x600. The software command I am using to send the screen's contents to the VGA output is
/usr/sbin/i855crt swcursor on 1024x768@60

[djcmackay]

So, I tried different resolutions (800x600, 640x480) and that didn't do any good; then I tried using a different software function to send the output to the VGA port, and THAT did make a difference. The mystery still remains: how come a 1024x768 display that displays fine on a computer projector is not deemed acceptable to the Tandberg? I'd still like to get to the bottom of this, because the change in software has got some downsides.

[Sean Lessman]

...how come a 1024x768 display that displays fine on a computer projector is not deemed acceptable to the Tandberg?

We have seen in the past that some video cards out there do not actually output what they say they output. Typically there are too many or too less number of lines or the refresh rate isn't actually 60Hz and so on. If your video card sending exactly 1024x768 and it is actually 60Hz -- it should work. I have never seen a video card that send the correct signal not work.

Sean