Howto setup dual screen for Compiz in Ubuntu Hardy

If you need to give presentations with your laptop and you are running Ubuntu Hardy, you might find that the gnome-display-properties (System>Preferences>Screen Resolution) do not work out of the box. So it is impossible to connect a beamer unless you clone. The same is true for a dual screen setup with Compiz.



There is however a very easy trick to solve this. I have tested it with an Asus Eee PC 701 4G and with my Ati Radeon X600 desktop system. I am now enjoying running dual screen with all the 3d desktops enabled.

The problem is that the default screen size configuration is too small, which does not allow you to place too screens next to each other. On the other hand Compiz can not handle texture sizes bigger than 2048x2048, which means for example two monitors of 1024x768. If you want to use bigger resolution, it is still possible, but you will need to turn off compiz and will loose the 3d effects.

So to solve it, fire up a terminal:

$ sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf.backup
$ sudo gedit /etc/X11/xorg.conf

Then find the "Screen" section and change it like this:

Section "Screen"
 Identifier "Default Screen"
 Monitor  "Configured Monitor"
 Device  "Configured Video Device"
 SubSection "Display"
  Virtual 2048 2048 
 EndSubSection
EndSection

To undo, you can just type:

$ sudo cp /etc/X11/xorg.conf.backup /etc/X11/xorg.conf

After doing this, you will be able to use gnome-display-properties with ease and run dual screen setups like this:

How to write a wxPython video player with Gstreamer

wxPython ships by default with the wx.MediaCtrl for very basic playback of music or videos. As I would like to do more advanced video manipulation, I was curious if I could use Gstreamer directly in wxPython to create my own pipelines. It was surprisingly easy.
For those who don't know Gstreamer, I quote the website (http://www.gstreamer.org):

GStreamer is a library that allows the construction of graphs of media-handling components, ranging from simple playback to complex audio (mixing) and video (non-linear editing) processing. Applications can take advantage of advances in codec and filter technology transparently.

There are python bindings for it, of which the documentation can be found on http://pygstdocs.berlios.de
I would also suggest to read these introductions to gstreamer & python:

• Introducing Gstreamer
• Getting started with GStreamer with Python
• Using Gnonlin with GStreamer and Python

I translated the video player example 2.2 of the tutorial from pyGtk to wxPython:
http://pygstdocs.berlios.de/pygst-tutorial/playbin.html

It should be straightforward to use this as a base for implementing your own pipelines. I work on Ubuntu, where I could install everything straight from the standard repositories.

Here is the source code:

#!/usr/bin/env python
#Example 2.2 http://pygstdocs.berlios.de/pygst-tutorial/playbin.html

import sys, os
import wx
import pygst
pygst.require("0.10")
import gst

import gobject
gobject.threads_init()

class WX_Main(wx.App):
  
   def OnInit(self):
       window = wx.Frame(None)
       window.SetTitle("Video-Player")
       window.SetSize((500, 400))
       window.Bind(wx.EVT_CLOSE,self.destroy)
       vbox = wx.BoxSizer(wx.VERTICAL)
       hbox = wx.BoxSizer(wx.HORIZONTAL)
       self.entry = wx.TextCtrl(window)
       hbox.Add(self.entry, 1, wx.ALL|wx.ALIGN_CENTER_VERTICAL, 4)
       self.button = wx.Button(window,label="Start")
       hbox.Add(self.button, 0, wx.ALL|wx.ALIGN_CENTER_VERTICAL, 4)
       self.button.Bind(wx.EVT_BUTTON, self.start_stop)
       vbox.Add(hbox, 0, wx.EXPAND, 0)
       self.movie_window = wx.Panel(window)
       vbox.Add(self.movie_window,1,wx.ALL|wx.EXPAND,4)
       window.SetSizer(vbox)
       window.Layout()
       window.Show()
       self.SetTopWindow(window)
      
       self.player = gst.element_factory_make("playbin", "player")
       bus = self.player.get_bus()
       bus.add_signal_watch()
       bus.enable_sync_message_emission()
       bus.connect('message', self.on_message)
       bus.connect('sync-message::element', self.on_sync_message)
      
       return True
      
   def start_stop(self, event):
       if self.button.GetLabel() == "Start":
           filepath = self.entry.GetValue()
           if os.path.exists(filepath):
               self.button.SetLabel("Stop")
               self.player.set_property('uri',"file://" + filepath)
               self.player.set_state(gst.STATE_PLAYING)
       else:
           self.player.set_state(gst.STATE_NULL)
           self.button.SetLabel("Start")
                      
   def on_message(self, bus, message):
       t = message.type
       if t == gst.MESSAGE_EOS:
           self.player.set_state(gst.STATE_NULL)
           self.button.SetLabel("Start")
       elif t == gst.MESSAGE_ERROR:
           self.player.set_state(gst.STATE_NULL)
           self.button.SetLabel("Start")
  
   def on_sync_message(self, bus, message):
       if message.structure is None:
           return
       message_name = message.structure.get_name()
       if message_name == 'prepare-xwindow-id':
           imagesink = message.src
           imagesink.set_property('force-aspect-ratio', True)
           imagesink.set_xwindow_id(self.movie_window.GetHandle())
          
   def destroy(self,event):
       #Stop the player pipeline to prevent a X Window System error
       self.player.set_state(gst.STATE_NULL)
       event.Skip()
          
app = WX_Main()
app.MainLoop()

How to change or recreate your Desktop folder on Ubuntu

The default location of your Desktop folder is ~/Desktop. You might prefer another location. If you by accident deleted the Dekstop folder, it will be stuck in your Trash folder as you can't put it back. These two steps enable you to change or restore your desktop folder:

gedit ~/.config/user-dirs.dirs
killall nautilus

In step 1 look for this entry: XDG_DESKTOP_DIR. Make it like this: XDG_DESKTOP_DIR="$HOME/Desktop"
Instead of step 2 you might also log off and log in again.

This is only tested on Gutsy.

How to install pymedia on Ubuntu (Gutsy)

"Pymedia is a Python library for accessing and manipulating media files. It makes audio and video playback/creation a snap for even a newcomer to programming." There is a deb installer available for pymedia 1.3.5 but not for 1.3.7 So I decided to write this howto.

First install all the dependencies:

sudo apt-get install python-dev libogg-dev libvorbis-dev liblame-dev libfaad2-dev libasound2-dev python-pygame

(Pygame is not really necessary, but recommended.)

Extract a download of pymedia-*.tgz and open a terminal in the extracted folder, so we can build pymedia:

python setup.py build

This should display:

Using UNIX configuration...

OGG : found
VORBIS : found
FAAD : found
MP3LAME : found
VORBISENC : found
ALSA : found
Continue building pymedia ? [Y,n]:

If everything is found press Y

Finally install pymedia:

sudo python setup.py install

Test if pymedia installed correctly by typing this at the python shell:

import pymedia

You may now proceed to the pymedia tutorials.

How to switch between python2.4 and python2.5 on Ubuntu

The default version of python on Edgy is python2.4 and on Feisty is python2.5 If you installed both versions of python and want to switch between them you have once to type this in a terminal:

sudo update-alternatives --install /usr/bin/python python /usr/bin/python2.4 10
sudo update-alternatives --install /usr/bin/python python /usr/bin/python2.5 1

Afterwards you can choose at any time your standard python version by:

sudo update-alternatives --config python

SPE now works on wxPython2.8 and how to switch

Today I switched on my laptop from wxPython2.6 to wxPython2.8 SPE seemed to work quite OK already, except: the bottom panel took too much place and was not draggable to a smaller size. After fixing this annoying bug, I am happily coding now with SPE on wxPython 2.8 For those who want to try out before I release, follow the subversion instructions. I tested the new SPE on Ubuntu (wxPython 2.6 & 2.8) and on Windows (wxPython 2.8). If anybody knows a good subversion client for the Mac, please comment.

sudo wxPython 2.8 has major new features such as AUI (Advanced User Interface), anti-alias graphics (Graphicscontext) and a lot of new widgets (RichTextCtrl, CustomTreeCtrl, SearchCtrl a la Firefox, ...). This might be useful for SPE in the future, but at the moment SPE stays backwards compatible with wxPython 2.6.


On Feisty wxPython is already included in repositories, just type:

sudo apt-get install python-wxgtk2.8

On Edgy you need to use the wxPython coummunity repositories. Open /etc/apt/sources.list:

sudo gedit /etc/apt/sources.list

Add the following lines:

# wxPython APT repository at wxcommunity.com
deb http://wxpython.wxcommunity.com/apt/ubuntu/dapper /
deb-src http://wxpython.wxcommunity.com/apt/ubuntu/dapper /

Then copy and paste these lines in a terminal:

sudo apt-get update
sudo apt-get dist-upgrade
sudo apt-get install python-wxgtk2.8 python-wxtools wx2.8-i18n

If you want to use XRC gui designer, you need python-xml:

sudo apt-get install python-xml

How to download the latest SPE from subversion

If you want to have the latest version of SPE, use subversion which is very easy. Do not forget first to uninstall your previous version of SPE! Windows users can uninstall SPE through 'Add/Remove programs' in the Control Panel (look for 'python-spe*', not for 'spe') and use a subversion client (tortoisesvn, rapidsvn) to get the latest SPE. Linux and mac users need just to copy and paste this in the terminal:

svn checkout svn://svn.berlios.de/python/spe/trunk/_spe

This will create a '_spe' folder. (Do not rename it to 'spe' or another name!) From this folder you can run:

python SPE.py

To browse the subversion repository online, surf to:

http://svn.berlios.de/wsvn/python/spe/trunk/_spe/

For ubuntu: to first remove SPE, type this in the terminal:

sudo apt-get remove spe kiki wxglade

To install subversion (svn), type this in the terminal:

sudo apt-get install subversion

Instructions for Tortoise SVN (thanks Richard):

1. Go to the location you want to download SPE to
2. Right click -> SVN Checkout
3. Paste svn://svn.berlios.de/python/spe/trunk/_spe into the url field
4. Click ok and it should work.