View source for Guidelines and HOWTOs/Debugging/Phonon

= Building Phonon from source =

If you want to have a newer Phonon build than 4.4.3 which is currently shipped by most distributions in KDE 4.6, you can build from source (git). Phonon is now located on git.kde.org.

== Get Dependencies ==

Deb-based distros, run <pre>sudo apt-get build-dep phonon</pre>to be sure you have all dependencies installed.
<br>
OpenSuSE:<pre>sudo zypper si -d phonon</pre>

== Install git ==

In Kubuntu, Debian, etc.:<pre>sudo apt-get install git-core</pre>
In Archlinux:<pre>sudo pacman -Sy git</pre>
In Gentoo:<pre>sudo emerge -av dev-util/git</pre>
In OpenSuSE:<pre>sudo zypper install git</pre>

== Install ccache to speed up compilation ==

Install the package from your distribution and set the size of the cache to 2 GB with the command<pre>ccache -M 2G</pre>
This will take 2Gb of space in your local directory. Enable the use of ccache by adding it to your local .bashrc, described below.

== Define the PATH and local environment ==

Append the following to $HOME/.bashrc:<pre>
    export PATH=$HOME/kde/bin:$PATH
    export PATH=/usr/lib/ccache:$PATH
    export LD_LIBRARY_PATH=$HOME/kde/lib:$LD_LIBRARY_PATH</pre>

Reload your edited .bashrc:<pre>
    source $HOME/.bashrc</pre>
NOTE: if you are not using the bash shell, edit your proper shell config file (~/.zshrc or ~/.tcshrc or whatever it may be).

== Make KDE aware of Phonon’s location ==
<pre>
echo 'export KDEDIR=$HOME/kde' >> $HOME/.kde/env/myenv.sh
echo 'export KDEDIRS=$KDEDIR' >> $HOME/.kde/env/myenv.sh</pre>
Some distributions call the above folder $HOME/.kde4/ , such as OpenSuSE.

== Install locally==

Install in your $HOME dir):<pre>
mkdir $HOME/kde && cd kde && mkdir src && cd src

git clone git://anongit.kde.org/phonon

cd phonon && mkdir build && cd build

cmake -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=debugfull $HOME/kde/src/phonon

sudo make install</pre>

To update your build, it's even easier: <pre>
cd ~/kde/src/phonon

git pull

cd build && sudo make install</pre>

== Build locally from a tarball ==

This is 4.4.4 for example:<pre>
cd ~/kde/src/

wget http://download.kde.org/download.php?url=stable/phonon/4.4.4/src/phonon-4.4.4.tar.bz2

tar xf phonon-4.4.4.tar.bz2

cd phonon-4.4.4 && mkdir build && cd build

cmake -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=debugfull $HOME/kde/src/phonon-4.4.4

sudo make install</pre>

= Environment Variables =

In general, there is one easy way to give Phonon devs all the information they need to help fix your problem.

Set these environment variables:
<pre>
$ export PHONON_DEBUG=5
$ export PHONON_PULSEAUDIO_DEBUG=5
$ export PHONON_VLC_DEBUG=5
$ export PHONON_GST_DEBUG=5
$ export PHONON_XINE_DEBUG=5
</pre>

Then run your program. The terminal will fill up with gobs of debugging output.

== Phonon-GStreamer debugging ==

=== Even more verbose output ===

Phonon-gst has some fancier debug options available. In addition to PHONON_GST_DEBUG, there is PHONON_GST_GST_DEBUG. Setting it to 8 or so will cause the gstreamer libraries to produce ''copious'' quantities of debug output. We're talking thousands of lines of what seems to be useless noise. Roughly 1% of it is useful, but the phonon-gst devs can easily decipher it and drill down to the important bits.

=== Pulseaudio ===

Pulseaudio and phonon try their hardest to get along. Sometimes, it doesn't work. Luckily, there is a way to test gstreamer and pulseaudio to see who is at fault.

<pre>
$ gst-launch filesrc location=/usr/share/sounds/KDE-Sys-Log-In.ogg ! decodebin2 ! audioresample ! audioconvert ! pulsesink
$ gst-launch filesrc location=/usr/share/sounds/KDE-Sys-Log-In.ogg ! decodebin2 ! audioresample ! audioconvert ! alsasink
</pre>

If they both work flawlessly, blame Phonon-GStreamer.

If the first works but the second doesn't, you might have an exotic sound setup that involves tweaking the alsasink parameters to reflect what pulseaudio does to alsa.

If the second works but the first doesn't, you can blame pulseaudio.

Another way to confirm this is by setting the PHONON_GST_AUDIOSINK environment variable. Setting it to e.g. "pulsesink" uses the pulseaudio sink.

=== Recreating the phonon-gst pipeline ===

Phonon-GStreamer creates predicable pipelines. In general, they look like this:

<!-- FIXME: We need a nice diagram -->

<pre>
filesrc -> decodebin2 -> queue -> audioresample -> audioconvert -> pulsesink
                   \
                    -> ffmpegcolorspace -> queue -> xvimagesink
</pre>

If the input stream isn't coming from a file, it is likely coming in via KIO which pipes it into an abstractmediastream. If pulseaudio isn't used, then replace pulsesink with something of alsasink, osssink, or somesuch.

Recreating the playback stream of some video file can be done as such:
<pre>
$ gst-launch filesrc location=/path/to/video ! decdebin2 name=dec ! audioresample ! audioconvert ! pulsesink \
    dec. ! ffmpegcolorspace ! xvimagesink
</pre>

DVD playback is a bit different:
<pre>
  (subpicture stream)
      /--->---\
rsndvdbin -> dvdspu -> ffmpegcolorspace -> queue -> xvimagesink
      \-> queue -> audioresample -> audioconvert -> pulsesink
</pre>

This is built with the following:
<pre>
$ gst-launch rsndvdbin ! dvdspu ! ffmpegcolorspace ! queue ! xvimagesink \
    rsndvdbin0 ! dvdspu0.subpicture \
    rsndvdbin0 ! queue ! audioresample ! audioconvert ! pulsesink
</pre>