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Old 10-30-09, 12:22 AM   #1
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Default Several problems with >2 head

Today, I assembled my four head workstation (dual G92/GTS 250's):


The display second from the left is the "main" display, on which appears GDM at startup, and (by default) my Gnome menu bar. The left display will primarily be used for watching video using mplayer, MythTV, and Flash (for hulu and mlb.tv). The right two displays will be used for vertical emacs windows for development.

I am using Ubuntu Karmic with nvidia kernel module 185.18.36, and fvwm (2) is my window manager.

The problems:

(1) TwinView is basically unusable in this configuration, as far as I can tell: if one uses TwinView for each Device, one ends up having to use Xorg Xinerama to stitch the two displays together (something that the nvidia-settings utility, in fact, sets up when you configure it in the obvious way), which results in two Xinerama screens, each spanning two monitors. This is unhelpful, as I want four Xinerama screens for practical purposes. The README seems to imply this, as it says that once Xorg's Xinerama is in use, the Xinerama emulation and geometry provided by TwinView goes away. I'm wondering if there is a work around for this (specifying the Xinerama screen geometries explicitly so I can get four of them), or if TwinView is really unusable in this configuration.

(2) In lieu of TwinView, I specified four Devices, one for each of the two screens of each video card, and the stitched them together using Xorg Xinerama. This works great from a geometry standpoint, except that mouse cursor (maybe focus?) transitions between the main display and other displays (!!) cause the video to briefly stutter/pause. I can live with this, but I don't think I should have to. Does anyone understand what I am talking about? In MythTV, I've tried OpenGL and XVideo-blit output, both with and without OpenGL vsync, and in no case does the problem disappear, though the problem seems to be less extreme with Xv-blit, though the video output uses more CPU than in OpenGL mode. I've not tried VDPAU, because I'm still using MythTV-0.22, which doesn't have official VDPAU support. (Is VDPAU expected to address this?) I have also not tried XvMC, because in the past it's always been more trouble than it's worth.

(3) This is more of a general Xinerama question, but I figured people here might have an idea of how to solve this. If I maximize a window in one of the two vertical displays on the right, the bounding box is limited by the top of the Gnome menu bar on the main display. Is this a peculiarity of fvwm?

I've attached my xorg.conf.
Attached Files
File Type: txt xorg.conf.txt (4.4 KB, 96 views)
happyfunbot is offline   Reply With Quote
Old 10-30-09, 01:44 AM   #2
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Join Date: Jul 2005
Location: Munich
Posts: 910
Default Re: Several problems with >2 head

Originally Posted by happyfunbot View Post
I'm wondering if there is a work around for this (specifying the Xinerama screen geometries explicitly so I can get four of them), or if TwinView is really unusable in this configuration.
If bad hacks count as work arounds, then you may like to have a look at this one:
(check posting #10).


JaXXoN is offline   Reply With Quote

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