Qt: no playback on linux

Question

I have tried (I think) every possible way of playing audio in a Qt project, none of which have worked:

• QSound::play(...)
• QMediaPlayer
• QAudioOutput, from http://doc.qt.io/qt-4.8/qaudiooutput.html

None of these solutions play WAV or MP3, and I have tried loading the files from a resource ( qrc:media/file.wav ) or simply from disk ( /full/path/to/file.wav ).

I think the problem is with codecs. QAudioDevice::supportedCodecs() returns an empty list. I'm on a linux system that has no problems playing audio/video (Ubuntu 14.04, usually playing in VLC... that uses its own codecs?).

Playing with QSound (WAV & MP3):

QSoundEffect(pulseaudio): Error decoding source

QMediaplayer (WAV): nothing happens

QMediaplayer (MP3):

GStreamer; Unable to play - "qrc:media/lowtone.mp3"

Answer 1

Qt uses specific media backends for each platform(link is qt5, but it was the same in Qt4). From the error it looks like your version is using GStreamer .

Check if the gstreamer dev packages on your distribution are well installed, because QAudioDevice::supportedCodecs must return at least audio/pcm . Work on the package setup until your test program show pcm . See https://wiki.qt.io/Building_Qt_for_Linux

You may also need to install plugins (also dev packages) before being able to play wav or mp3 using phonon.