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QMediaPlayer no video only audio



  • I'm trying to get the basic VideoPlayer example to run but I do not get any video, only audio (https://doc.qt.io/qt-5.11/qtmultimedia-multimediawidgets-videowidget-example.html). Hoping someone can give me some things to try. I'm running KDE on Ubuntu 18.04. I have tested all the videos I'm trying in other tools and they work just fine.

    Qt 5.11.2 (x86_64-little_endian-lp64 shared (dynamic) release build; by GCC 5.3.1 20160406 (Red Hat 5.3.1-6)) on "xcb"
    OS: Ubuntu 18.04.1 LTS [linux version 4.15.0-38-generic]



  • Ok - got it working. The Qt multimedia library installed with my linux distro (5.9.5) apparently doesn't work so I:

    • installed 5.11.2 in ~/qt5.11.2
    • ran a "make clean"
    • ran qmake from "~/qt5.11.2/gcc_64/bin/qmake"
    • ran make
    • export LD_LIBRARY_PATH="~/qt5.11.2/gcc_64/lib"
    • export QT_PLUGIN_PATH="~/qt5.11.2/gcc_64/plugins"
    • ran the application

    With 5.11.2 the video and audio appear to be working.

    Thanks for the help


  • Lifetime Qt Champion

    Hi and welcome to devnet,

    What kind of video is that ?
    Did you check that you have all of the GStreamer stuff installed ?



  • I tried with every type of video file I have locally, mov, avi, mp4, etc. I tried installing every gstreamer package I could get my hands on.

    ii gir1.2-gstreamer-1.0 1.14.1-1~ubuntu18.04.1 amd64 GObject introspection data for the GStreamer library
    ii gstreamer-qapt 3.0.4-0ubuntu1 amd64 GStreamer plugin to install codecs using QApt
    ii gstreamer1.0-alsa:amd64 1.14.1-1ubuntu1~ubuntu18.04.1 amd64 GStreamer plugin for ALSA
    ii gstreamer1.0-clutter-3.0:amd64 3.0.26-1 amd64 Clutter PLugin for GStreamer 1.0
    ii gstreamer1.0-doc 1.14.1-1~ubuntu18.04.1 all GStreamer core documentation and manuals
    ii gstreamer1.0-fluendo-mp3:amd64 0.10.32.debian-1 amd64 Fluendo mp3 decoder GStreamer 1.0 plugin
    ii gstreamer1.0-gl:amd64 1.14.1-1ubuntu1~ubuntu18.04.1 amd64 GStreamer plugins for GL
    ii gstreamer1.0-libav:amd64 1.14.1-1~ubuntu18.04.1 amd64 libav plugin for GStreamer
    ii gstreamer1.0-nice:amd64 0.1.14-1 amd64 ICE library (GStreamer plugin)
    ii gstreamer1.0-packagekit 1.1.9-1ubuntu2.18.04.3 amd64 GStreamer plugin to install codecs using PackageKit
    ii gstreamer1.0-plugins-bad:amd64 1.14.1-1ubuntu1~ubuntu18.04.1 amd64 GStreamer plugins from the "bad" set
    ii gstreamer1.0-plugins-base:amd64 1.14.1-1ubuntu1~ubuntu18.04.1 amd64 GStreamer plugins from the "base" set
    ii gstreamer1.0-plugins-base:i386 1.14.1-1ubuntu1~ubuntu18.04.1 i386 GStreamer plugins from the "base" set
    ii gstreamer1.0-plugins-base-apps 1.14.1-1ubuntu1~ubuntu18.04.1 amd64 GStreamer helper programs from the "base" set
    ii gstreamer1.0-plugins-good:amd64 1.14.1-1ubuntu1~ubuntu18.04.1 amd64 GStreamer plugins from the "good" set
    ii gstreamer1.0-plugins-ugly:amd64 1.14.1-1~ubuntu18.04.1 amd64 GStreamer plugins from the "ugly" set
    ii gstreamer1.0-pulseaudio:amd64 1.14.1-1ubuntu1~ubuntu18.04.1 amd64 GStreamer plugin for PulseAudio
    ii gstreamer1.0-tools 1.14.1-1~ubuntu18.04.1 amd64 Tools for use with GStreamer
    ii gstreamer1.0-vaapi:amd64 1.14.1-1~ubuntu18.04.1 amd64 VA-API plugins for GStreamer
    ii gstreamer1.0-x:amd64 1.14.1-1ubuntu1~ubuntu18.04.1 amd64 GStreamer plugins for X11 and Pango
    ii libgstreamer-gl1.0-0:amd64 1.14.1-1ubuntu1~ubuntu18.04.1 amd64 GStreamer GL libraries
    ii libgstreamer-plugins-bad1.0-0:amd64 1.14.1-1ubuntu1~ubuntu18.04.1 amd64 GStreamer libraries from the "bad" set
    ii libgstreamer-plugins-base1.0-0:amd64 1.14.1-1ubuntu1~ubuntu18.04.1 amd64 GStreamer libraries from the "base" set
    ii libgstreamer-plugins-base1.0-0:i386 1.14.1-1ubuntu1~ubuntu18.04.1 i386 GStreamer libraries from the "base" set
    ii libgstreamer-plugins-base1.0-dev 1.14.1-1ubuntu1~ubuntu18.04.1 amd64 GStreamer development files for libraries from the "base" set
    ii libgstreamer-plugins-good1.0-0:amd64 1.14.1-1ubuntu1~ubuntu18.04.1 amd64 GStreamer development files for libraries from the "good" set
    ii libgstreamer1.0-0:amd64 1.14.1-1~ubuntu18.04.1 amd64 Core GStreamer libraries and elements
    ii libgstreamer1.0-0:i386 1.14.1-1~ubuntu18.04.1 i386 Core GStreamer libraries and elements
    ii libgstreamer1.0-dev 1.14.1-1~ubuntu18.04.1 amd64 GStreamer core development files
    ii libreoffice-avmedia-backend-gstreamer 1:6.0.6-0ubuntu0.18.04.1 amd64 GStreamer backend for LibreOffice
    ii phonon-backend-gstreamer:amd64 4:4.9.0-1 amd64 Phonon GStreamer 1.0 backend
    ii phonon-backend-gstreamer-common:amd64 4:4.9.0-1 amd64 Phonon GStreamer 1.0.x backend icons
    ii phonon4qt5-backend-gstreamer:amd64 4:4.9.0-1 amd64 Phonon Qt5 GStreamer 1.0 backend



  • Tried uninstalling all gstreamer related packages. Once uninstalled the application core dumps. I reinstalled everything and it's back to showing a black video window. Audio works fine.


  • Lifetime Qt Champion

    Does it do the same with your distribution provided Qt ?



  • Thanks for the help! All of my testing had been with the distribution qt (version 5.9.5). I installed 5.11.2, and 5.0.2 and had the same results.



  • Ok - got it working. The Qt multimedia library installed with my linux distro (5.9.5) apparently doesn't work so I:

    • installed 5.11.2 in ~/qt5.11.2
    • ran a "make clean"
    • ran qmake from "~/qt5.11.2/gcc_64/bin/qmake"
    • ran make
    • export LD_LIBRARY_PATH="~/qt5.11.2/gcc_64/lib"
    • export QT_PLUGIN_PATH="~/qt5.11.2/gcc_64/plugins"
    • ran the application

    With 5.11.2 the video and audio appear to be working.

    Thanks for the help


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