[Interest] Phonon video

R. Reucher rene.reucher at batcom-it.net
Thu Mar 29 15:57:05 CEST 2012

Phonon is highly dependent on the back-end and in case of the video-player, 
especially on the quality of the available codecs... on Windows, I've had best 
results with the codecs from


I can assure you that Phonon still works this week :). But surely, Windows 
updates can ruin your live... and it's not a problem of Qt / Phonon.

HTH, René

On Thursday 29 March 2012 14:34:42 Bo Thorsen wrote:
> Hi people,
> I've been trying to figure out why phonon suddenly doesn't work anymore.
> It plays audio just fine but not video. I'm completely stuck.
> I built and ran the qmediaplayer demo and saw the same thing, so it's
> not my code. And the same code plays the files just fine on Linux. But
> just for reference, here it is anyway:
>      mPlayer = new Phonon::MediaObject(this);
>      mVideo = new Phonon::VideoWidget;
>      Phonon::createPath(mPlayer, mVideo);
>      if (!mPlayer->hasVideo()) {
>          qDebug() << "Phonon video sink is not available";
>          ...
>      }
> hasVideo() returns false, and any attempt at adding a video file to
> Phonon gives me a "Pause Called" in the debug output window. This is the
> code used to play a file:
>      mVideo->show();
>      mVideo->resize(200, 200);
>      mPlayer->enqueue(Phonon::MediaSource(filename));
>      mPlayer->play();
> Calling Phonon::BackendCapabilities::availableMimeTypes() gives me a
> list of 54 mimetypes with both audio and video types in it. The files
> I'm trying to play are supported, and Windows Media Player plays them
> just fine.
> Now here's the really strange part: Last week it worked. But suddenly,
> video playback is gone. I have no clue what happened in between. I might
> have updated Windows, but if that breaks Phonon, we have a real problem.
> I can see that the DS94 backend is still there in both my 4.8.0 and
> 4.7.4 plugins.
> This really worries me. The code is for a customer with an embedded
> system that's going to be deployed on machines in many countries.
> Calling those back to fix a Phonon problem *is not* an option. If Phonon
> can't deliver a stable environment (and I currently seriously doubt
> this), I will have to ditch it.
> I obviously tried to search the net for this, and found plenty of people
> with the same result. But none with a solution for it. I hope someone
> here can help.
> I'm on Windows 7 x64 and Windows XP 32 bit, using a fully updated SDK
> 2.4.1 with both visual studio 8 and mingw compilers and Qt versions
> 4.8.0 and 4.7.4.
> Bo Thorsen,
> Fionia Software.
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