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| This page is a draft that need worked on. Eventually, it'll end up on Techbase as a one-stop shop to send people to when they're having phonon problems.
| | Moved to http://techbase.kde.org/Development/Tutorials/Debugging/Phonon on Mar 8, 2011 --tdfischer |
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| = Environment Variables =
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| In general, there is one easy way to give Phonon devs all the information they need to help fix your problem.
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| Set these environment variables:
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| <pre>
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| $ export PHONON_VLC_DEBUG=5
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| $ export PHONON_GST_DEBUG=5
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| </pre>
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| Then run your program. The terminal will fill up with gobs of debugging output.
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| == Phonon-GStreamer debugging ==
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| === Even more verbose output ===
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| 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.
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| === Pulseaudio ===
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| 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.
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| <pre>
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| $ gst-launch filesrc location=/usr/share/sounds/KDE-Sys-Log-In.ogg ! decodebin2 ! audioresample ! audioconvert ! pulsesink
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| $ gst-launch filesrc location=/usr/share/sounds/KDE-Sys-Log-In.ogg ! decodebin2 ! audioresample ! audioconvert ! alsasink
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| </pre>
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| If they both work flawlessly, blame Phonon-GStreamer.
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| 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.
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| If the second works but the first doesn't, you can blame pulseaudio.
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| Another way to confirm this is by setting the PHONON_GST_AUDIOSINK environment variable. Setting it to e.g. "pulsesink" uses the pulseaudio sink.
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| === Recreating the phonon-gst pipeline ===
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| Phonon-GStreamer creates predicable pipelines. In general, they look like this:
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| <!-- FIXME: We need a nice diagram -->
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| <pre>
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| filesrc -> decodebin2 -> queue -> audioresample -> audioconvert -> pulsesink
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| \
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| -> ffmpegcolorspace -> queue -> xvimagesink
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| </pre>
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| 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.
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| Recreating the playback stream of some video file can be done as such:
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| <pre>
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| $ gst-launch filesrc location=/path/to/video ! decdebin2 name=dec ! audioresample ! audioconvert ! pulsesink \
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| dec. ! ffmpegcolorspace ! xvimagesink
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| </pre>
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| DVD playback is a bit different:
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| <pre>
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| (subpicture stream)
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| /--->---\
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| rsndvdbin -> dvdspu -> ffmpegcolorspace -> queue -> xvimagesink
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| \-> queue -> audioresample -> audioconvert -> pulsesink
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| </pre>
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| This is built with the following:
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| <pre>
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| $ gst-launch rsndvdbin ! dvdspu ! ffmpegcolorspace ! queue ! xvimagesink \
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| rsndvdbin0 ! dvdspu0.subpicture \
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| rsndvdbin0 ! queue ! audioresample ! audioconvert ! pulsesink
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| </pre>
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