Camera viewfinder fails to load in Lubuntu 14.04

[uranusjr]

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?

Thanks.

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

[stuartx]

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

[uranusjr]

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. :(

[stuartx]

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.

[uranusjr]

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.