Gentoo blocked libav and ffmpeg

Tuesday, March 3rd, 2015

Well gentoo needs you to chose ffmpeg or libav for update deep worlds to work. My system was moaning that libav + ffmeg were blocking each other.

The error is something like this :

[blocks B ] media-video/ffmpeg ("media-video/ffmpeg" is blocking

* Error: The above package list contains packages which cannot be
* installed at the same time on the same system.

(media-video/ffmpeg-0.10.2::gentoo, ebuild scheduled for merge)
pulled in by media-video/ffmpeg required by @selected

(media-video/libav-0.8.2::gentoo, ebuild scheduled for merge) pulled
in by
required by (virtual/ffmpeg-0.10.2-r1::gentoo, ebuild scheduled for

I decided to use libav. Which appears to be the more active and stably developed.

I simply added -ffmpeg to my USE flag in /etc/portage/make.conf.

E.g :

USE="$USE -ffmpeg" #use libav

Then I removed ffmpeg from my system

sudo emerge -C media-video/ffmpeg
sudo emerge -C virtual/ffmpeg

Next was the big emerge

sudo emerge -avuDN world

which now no longer moans about blocking packages.

Minecraft 1.8.2 – ArrayIndexOutOfBoundsException at LinuxDisplay.getAvailableDisplayModes()

Thursday, February 19th, 2015

I tried to play minecraft 1.8.2 this evening, only to have it crash on every startup with :

Time: 19/02/15 18:58
Description: Initializing game

        at avf.a(SourceFile:310)
        at net.minecraft.client.main.Main.main(SourceFile:124)
Caused by: java.lang.ArrayIndexOutOfBoundsException: 0
        at org.lwjgl.opengl.LinuxDisplay.getAvailableDisplayModes(
        at org.lwjgl.opengl.LinuxDisplay.init(
        at org.lwjgl.opengl.Display.(
        ... 4 more

The cause seems to be the move from lwjgl 2.9.1 to 2.9.4 with Minecraft 1.8.2.

After a lot of debugging and swearing from me, Steve found out that it was an issue with my dual monitors. Installing xrandr fixes lwjgl and then allows minecraft to start.

The issue comes from this line in the XRandR class which doesnt throw any exception when the command isnt available.  Parsing command line output from a child process in Java is really a bad idea.


* Utility for working with the xrandr commmand-line utility. Assumes
* xrandr v1.2 or higher.

Crazy mouse speed fix

Tuesday, January 6th, 2015

I recently bought a Logitech Business Mouse but when I plugged into my desktop (running Gentoo Linux) it was running at ludicrous speed.

When I opened the “Mouse and Touchpad” UI and tried changing the Acceleration down from 2.0 to 0.1.

Default XFCE mouse speedThis made the mouse better but I didn’t like how it felt.  I cant really describe what was wrong with it.

I found this blog which said I could enable “Constant Deceleration” to fix this issue so I ran :

xinput --list

which lists the core pointers

Virtual core pointer                    	id=2	[master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer              	id=4	[slave  pointer  (2)]
⎜   ↳ Logitech USB Optical Mouse              	id=12	[slave  pointer  (2)]

I then ran :

xinput -set-prop "Logitech USB Optical Mouse" "Device Accel Constant Deceleration" 2.5

which slows down the 800dpi to be closer to my older mouse.    This meant the mouse was working the same my old Dell one but it wasnt being remembered after a reboot.

Created /etc/X11/xorg.conf.d/50-mouse-acceleration.conf with the following contents

Section "InputClass"
   Identifier "Logitech USB Optical Mouse"
   MatchIsPointer "true"
   MatchProduct "Logitech USB Optical Mouse"
   Option "ConstantDeceleration" "2.5"

Note : sudo emerge -av x11-apps/xinput

Blender and the Space Navigator under Gentoo

Saturday, May 22nd, 2010

I have used Blender for some years now and I recently began to think about buying a 3dconnexion Space Navigator.

I read that Blender and the Space Navigator worked under Linux and managed to borrow a Space Navigator from work over this long weekend.

I downloaded the 32bit drivers (3DxWare for Linux (i386)) from as well as the “Blender plug-in for Linux i386 (beta)

Installing the Space Navigator driver

I extracted the 3dxware-linux-v1-4-3.i386.tar.gz file to /tmp/3d/

tar -xvzf 3dxware-linux-v1-4-3.i386.tar.gz -C /tmp/3d/
cd /tmp/3d/
sudo ./

I then recieved an error saying was missing.

/etc/3DxWare/daemon/3dxsrv: error while loading shared libraries: cannot open shared object file: No such file or directory

I pressed CTRL-C to abort the script.

After a little checking I found that I have but not 3, so I created a symbolic link from libXm 4 to 3.

sudo ln -s /usr/lib/ /usr/lib/

I then re-ran the install script again.

This time it all worked.  I did not configure it to auto start though.

Now I simply started the driver via

sudo /etc/3DxWare/daemon/3dxsrv -d usb

and was greeted by the blue lights on the Space Navigator and the messages

3DxWareUNIX = V1.4.3
Device      = SpaceNavigator
Firmware    = V3.17

there was also a minimised window called 3DxWare 1.4.3, which appears the be the settings dialog (like the Windows Control Panel control)

I then ran the xcube example from /tmp/3d/ and the space navigator worked great.  I changed a few settings as I prefer pressing and pulling to be zoom in and out.

Installing the Blender plugin

I was a little surprised by this, as the forums said I should have a ~/.blender/ directory and I didnt.

I decided that creating the directory couldn’t cause any problems so I created a directory

mkdir -p ~/.blender/plugins/

and copied the 3DxNdofBlender.plug file into it.  The new NDOF icons appeared at the bottom of the viewport.  See

Home and End key with rxvt

Tuesday, March 31st, 2009

I use cygwins rxvt at work and have had problems with the End and Home key not working.

I also had the same issue at home using rxvt-unicode on gentoo.

After lots of search last night I finally found the fix for urxvt.

Simply add this to your ~/.inputrc file

# home and end keys for rxvt

I then tried this at work this morning and found it works on cygwins rxvt too.