Too Far Afield » ubuntu

Choppy Flash video in full-screen mode on Ubuntu

Patrick — Wed, 19 Aug 2009 00:59:57 +0000

When I originally upgraded to Ubuntu 9.04 (Jaunty), I noticed that Flash video in full-screen mode was kind of choppy. I never took the time to debug this and instead worked around this by either not watching Flash videos in full screen mode, not watching Flash videos at all or using the excellent Youtube integration of Totem. However, today I did some research into the problem and found a bug in Launchpad, which solved the problem for me. It turns out that there is a bug affecting the Intel stack (in this case Intel stack means not necessarily an Intel graphics card, but Intel processor). The bug is a miscommunication between X.org and the Kernel, which results in a misconfiguration of the Memory Type Range Registers (MTRR) in the Kernel. The result is poor performance in video playback and everything that involves graphics in general. This bug has been fixed upstream and in Karmic. A fix for Jaunty has been developed, but is yet to be released.

You can test, if you are affected, by running cat /proc/mtrr on the command line. If you can’t see a line, which ends in write-combining you are most certainly affected by this. You can further check with lspci -vv and check the Region 0 memory range of your VGA adaptor. If you cant find that memory range in your mtrr file, you are probably affected.

Until the fix is released, one solution is to run this shell script as root after every restart of your X.org server. Warning: Audit any external file before you run it as root on your computer! The script should update the MTRR configuration of the Kernel with the correct settings. If you are affected by the bug, you will notice a slight improvement in overall graphics performance and the full-screen Flash videos should now play as originally intended.

Add missing GPG public key to Debian’s apt

Patrick — Mon, 08 Jun 2009 05:49:57 +0000

Just a quick post, because I always have to look it up: If you get a message like this while installing a new package through apt…

W: GPG error: http://ppa.launchpad.net intrepid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C514AF8E4BA401C3

… you can do the following to get rid of it:

gpg --keyserver pgpkeys.mit.edu --recv-key C514AF8E4BA401C3
gpg -a --export C514AF8E4BA401C3 | apt-key add -

Works on Ubuntu and other derivatives of Debian all the same, of course. Hope this post will safe me some time the next time I run into this.

Remove pages from PDF files on Linux

Patrick — Sun, 24 Dec 2006 19:24:03 +0000

Today I needed to remove some pages from a bunch of PDF files. In search of a tool, I came across the article Manipulating PDFs with the PDF Toolkit. To cut out pages 10-25 from a PDF type:

pdftk old.pdf cat 1-9 26-end output new.pdf

If you don’t have it already, you need to install the Ubuntu/Debian package pdftk first.

In related news: It’s Christmas. So merry Christmas to everyone. I will be quite busy between the years (a translation of zwischen den Jahren, an expression used in Germany to describe the time between Christmas and the first day of the new year). I will participate in a bunch of Christmas-related events today and tomorrow and will be at the 23rd Chaos Comminication Congress in Berlin from December 26. See you there!