Camera viewfinder fails to load in Lubuntu 14.04

  • Hi,

    I’m trying to use the camera viewfinder on Linux. The compilation works fine, but when I try to launch the program all I get is a black screen, with the following in stderr:

    @GStreamer-CRITICAL **: gst_object_ref_sink: assertion 'GST_IS_OBJECT (object)' failed@

    I tried both the Qt 5.2.1 from APT and 5.3.0 from the official online installer. Same result. I tried to install some stuff that seems related (libqt5multimedia5-plugins, for example), but nothing yields success. Is there something that I should install/compile to make this work?


    p.s. For what it’s worth, the same application works perfectly on my OS X machine with Homebrew Qt.

  • uranusjr, I get the same problem when running the camera example. Do you have a solution for this problem? Thanks.

  • I ended up switching to another Linux distribution (Linux Mint Qiana, for the record), and after installing libqtmultimedia5-plugins everything works fine.

    Since Mint Qiana and Lubuntu 14.04 are both based on Ubuntu 14.04, I suspect Lubuntu has some plugin and/or codec dependency missing somewhere out of the box. But I really can’t tell what. Sorry. :(

  • How to install libqtmultimedia5-plugins? How can I tell if it is installed on my box? I cannot find it in Qt maintainence tool. Thanks.

  • I used the Qt distribution provided by APT. If you use Ubuntu (or its derivatives like Mint), you can install Qt libraries with

    sudo apt-get install qt5-default libqt5multimediawidgets5 libqt5multimedia5-plugins

    You may or may not need more packages; these work for me. Also note that the package name in my previous post is wrong. Sorry.

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