use v4l2 overlay in qt application

MajidKamali

Hi.
I have a raspberry pi 3 B+ with qt 5.12.4 installed on it.
I want to use camera v1 module in qt.
v4l2 is installed and v4l2-ctl --overlay=1 shows camera output with awesome quality and frame rate.
Is there a way to use this overlay in Qt (preferably QML)? e.g. access shared memory or use opengl etc.
I want to call v4l2-ctl via QProcess and show live camera in my application. If you have a better alternative, I'm listening :)

Thanks

jsulm

@majidkamali Why not using https://doc.qt.io/qt-5/qcameraviewfinder.html instead of starting another process?

MajidKamali

@jsulm Camera does not work at all :-(
I created a simple widget program and copy code from QCameraViewfinder doc.
shows defaultServiceProvider::requestService(): no service found for - "org.qt-project.qt.camera" in console output :-(

jsulm

@majidkamali I think you need GStreamer and its plugins for QCamera

MajidKamali

all gstreamer plugins are installed via apt-get in raspberry pi
good, bad, ugly, qt plugin
Do I need to recompile Qt to recognize gstreamer? I am using a manually compiled Qt 5.12.4 (in /opt/Qt5.12), but system has Qt 5.11 via apt-get

SGaist

Hi,

Did you also install the GStreamer development packages ?

Otherwise your build is likely missing the related plugins.

MajidKamali

Did you also install the GStreamer development packages ?

Yes I did. from apt-get

Otherwise your build is likely missing the related plugins.

How can I figure it out? I did not add any multimedia related option in configure script for configuring compiled Qt 5.12.4. (no skip option used)

SGaist

You can check the content of the plugins folder of your custom Qt installation.

The detection is done when configure is run. If you added the development packages after having run configure, it won't detect it.

The tests logs will also contain these information.