Import Error when Integrating Qt and GStreamer.

Matthew Waters ystreet00 at
Tue Apr 6 02:11:18 UTC 2021

Ah, so your problem is use with the Qt designer not showing finding the 
relevant qml code.  That use case is currently not supported by qmlglsink.

The issue is that the necessary QML item is contained within the 
qmlglsink element itself and is registered dynamically when the element 
itself is instantiated.  Qt designer doesn't know anything about 
GStreamer so cannot perform this initialisation for you. There are no 
qmldir or qmltype files for qmlglsink.

The 'fix' involves are rather complicated restructure of the qmlglsink 
element to support placing the qml part/plugin in a separate .so that is 
findable with Qt tools (using qmldir or whatever).


On 6/4/21 11:22 am, iotsystek wrote:
> Thank you for your input, its greatly appreciated.
> When I attempted to install using: sudo apt install gstreamer1.0-qt5 as
> expected it shows as already being installed.
> /[sudo] password for ubuntu:
> Reading package lists... Done
> Building dependency tree
> Reading state information... Done
> gstreamer1.0-qt5 is already the newest version (1.14.5-0ubuntu1~18.04.1).
> The following packages were automatically installed and are no longer
> required:
>    linux-headers-5.4.0-62-generic linux-hwe-5.4-headers-5.4.0-42
> linux-hwe-5.4-headers-5.4.0-58 linux-hwe-5.4-headers-5.4.0-59
> linux-hwe-5.4-headers-5.4.0-60
>    linux-hwe-5.4-headers-5.4.0-62 linux-image-5.4.0-62-generic
> linux-modules-5.4.0-62-generic linux-modules-extra-5.4.0-62-generic
> Use 'sudo apt autoremove' to remove them.
> 0 upgraded, 0 newly installed, 0 to remove and 26 not upgraded.
> /
> When I run: gst-inspect-1.0 qmlglsink I get the expected output.
> /Factory Details:
>    Rank                     none (0)
>    Long-name                Qt Video Sink
>    Klass                    Sink/Video
>    Description              A video sink that renders to a QQuickItem
>    Author                   Matthew Waters <matthew at>
> Plugin Details:
>    Name                     qmlgl
>    Description              Qt gl plugin
>    Filename
> /usr/lib/x86_64-linux-gnu/gstreamer-1.0/
>    Version                  1.14.5
>    License                  LGPL
>    Source module            gst-plugins-good
>    Source release date      2019-05-29
>    Binary package           GStreamer Good Plugins (Ubuntu)
>    Origin URL
> GObject
>   +----GInitiallyUnowned
>         +----GstObject.............................You get the idea.
> /
> I say expected because my simple test code compiles and runs as expected
> displaying a video in a QML window.  This error is preventing me from being
> able to do any UI development using the designer.
> I found a short video regarding imports on Youtube.  From that and what I
> have read on other sites, could this problem be related to NOT having either
> plugins.qmltypes or qmldir files in the folder with the file?
> If so do you know where I could find those files?
> Do you have a working example?
> Thanks in advance for any further assistance.
> <>
> --
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> gstreamer-devel at

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