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Old 11-03-12, 06:05 PM   #1
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Join Date: Dec 2004
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Default Driving a projector with lap-top external video output

My apologies in advance for asking a question that I'm sure must have been asked many times before. I've spent hours Googl'ng, recently and on other occasions over the past few years, and haven't found quite what I'm looking for. I assume answers are out there, if I only I could find the right query... So my initial, general question is:

Can anyone point me to a reasonably up-to-date how-to, manual, man page, or similar that describes methods for driving a projector from the external video output of a Linux lap-top with a built-in nVidia graphics adapter? Generic (not nVidia-specific) info would be great too.

My use case is a bit different from those discussed in most of the things I've read, but I don't think it's unique. In fact it seems to be somewhat close to a home theatre kind of setup, perhaps on a larger scale. Here are the highlights...
  • For things like public presentations, it isn't acceptable to clone the built-in lap-top screen, or to see windows being dragged into and out of the screen. I need to be able to control exactly what appears on the output to the projector -- for example, when I play a video, I need the output to show only the video, full-screen. Xinerama might theoretically work, but I've had issues when I've tried it in the past (with KDE), such as the root window background showing up on the 2nd output (OK, I could use a black background), the task bar extending across the entire virtual display, and panning on one screen or the other due to the fact that the two displays don't have the same dimensions. So I'm assuming a separate X screen would work better -- from a terminal in the main screen / X session, I could launch an app like mplayer with DISPLAY set to the other screen, for example.
  • I need the projector to display nothing by default (ie, when no app is displaying anything there) -- but "nothing" here means a black screen, as opposed to no video signals being driven, because I don't want the projector to put up it's blue "no signal" screen and eventually drop back to stand-by mode (until I want it to).
  • In some cases, the projector is some distance from the computer -- for example, in a rear projection configuration -- where the color and sync signals from the VGA output are transmitted over Cat-5 cable using driver/receiver boxes that do not pass DDC/EDID data back from the device at the remote end. Therefore I need to be able to force video settings for the external output, and to make changes relatively easily/quickly, without having to hack xorg.conf. I'm fine with editing config files, running things from the command line, using/writing scripts, etc, but fiddling xorg.conf isn't acceptable because it requires restarting X, and that would kill the (usually many) things I have running on the main screen. In some situations, I have only minutes, if that, to get up and running with a given projector.
  • I need the video output format (pixel dimensions) to match the projector's native resolution, so that I don't get surprised by whatever it might do (scaling, cropping, etc) to cope with a signal that isn't. Some projectors' native resolutions, such as 1280x800, are not in the list of choices given by nvidia-settings, so I need a way to add them if they aren't in the default list.

    (This is OT, but sometimes nvidia-settings doesn't even get that far. Right now the "X Server Display Configuration" screen on my lap-top shows an error

    Unable to load X Server Display Configuration page:

    Failed to find display device 0x00000001 on screen 0 (on GPU-0)
    while parsing metamode:

    'CRT-0: NULL'
    although it didn't have this problem just yesterday and I'm pretty darn sure I haven't changed anything since then.)
  • It would be great to have a (scalable) copy of what's going to the second output available in a window on the primary display, as some commercial presentation software provides, but this isn't a minimum requirement.

Here's an example of equipment I'm currently using, although I've tried this before with other lap-tops and Linux releases, all without finding a good solution:
  • computer: HP Elitebook 8540w
  • graphics adapter (from lspci):
    01:00.0 VGA compatible controller: nVidia Corporation GT216 [Quadro FX 880M] (rev a2)
  • distro: Fedora 14 32-bit (kernel
  • nVidia driver: akmod-nvidia-280.13-2.fc14.i686
  • projector: Panasonic PT-DW730ULS

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