Webcam preview with Qt Quick
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wrote on 12 Aug 2016, 23:08 last edited by Aras 8 Dec 2016, 23:11
I am planning to embed a webcam view in my application. In order to understand how that works I tried running the declerative camera sample project. It builds and runs, however I do not see any video from camera -- the view is just black. In the application output inside Qt Creator, I see the following errors:
Starting /home/aras/Qt5.7.0/Examples/Qt-5.7/multimedia/build-declarative-camera-Desktop_Qt_5_7_0_GCC_64bit-Debug/declarative-camera... QML debugging is enabled. Only use this in a safe environment. defaultServiceProvider::requestService(): no service found for - "org.qt-project.qt.camera" defaultServiceProvider::requestService(): no service found for - "org.qt-project.qt.mediaplayer" qrc:///VideoCaptureControls.qml:110: Error: Cannot assign [undefined] to QString qrc:///CameraListButton.qml:65:5: QML CameraListPopup: Binding loop detected for property "currentValue" qrc:///PhotoCaptureControls.qml:135: Error: Cannot assign [undefined] to QString qrc:///CameraListButton.qml:65:5: QML CameraListPopup: Binding loop detected for property "currentValue" /home/aras/Qt5.7.0/Examples/Qt-5.7/multimedia/build-declarative-camera-Desktop_Qt_5_7_0_GCC_64bit-Debug/declarative-camera exited with code 0Why do you think the sample program is not working? Am I missing some libraries?
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wrote on 13 Aug 2016, 01:58 last edited by
Hi Aras,
Did you include multimedia (for QML) and/or multimediawidgets (for C++ QWidget code) in your .pro project file ?
Could you paste your code (you can use service paste from gist github maybe... this can be able to add many different files) ?
Or maybe if you have a public test-case application on git or bitbucket something like that, i would be happy to contribute.
Also, could you tell us wich environment you are running on ? (linux, Osx, Windows) -
Hi,
Do you have GStreamer installed ? If so which version ?
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wrote on 15 Aug 2016, 18:53 last edited by
@jerome_isAviable I am using the declarative camera sample app that comes with Qt installation without any modification, so I assume this is not an error in the code, but something with my environment.
I am using Ubuntu Linux 16.06 64bit. Here is are my gstreamer packages:
$ sudo dpkg -l |grep gstreamer ii gir1.2-gstreamer-1.0 1.8.2-1~ubuntu1 amd64 GObject introspection data for the GStreamer library ii gstreamer-qapt 3.0.2-0ubuntu1.1 amd64 GStreamer plugin to install codecs using QApt ii gstreamer1.0-alsa:amd64 1.8.2-1ubuntu0.1 amd64 GStreamer plugin for ALSA ii gstreamer1.0-clutter-3.0 3.0.18-1 amd64 Clutter PLugin for GStreamer 1.0 ii gstreamer1.0-fluendo-mp3:amd64 0.10.32.debian-1 amd64 Fluendo mp3 decoder GStreamer 1.0 plugin ii gstreamer1.0-libav:amd64 1.8.2-1~ubuntu1 amd64 libav plugin for GStreamer ii gstreamer1.0-plugins-bad:amd64 1.8.2-1ubuntu0.1 amd64 GStreamer plugins from the "bad" set ii gstreamer1.0-plugins-bad-faad:amd64 1.8.2-1ubuntu0.1 amd64 GStreamer faad plugin from the "bad" set ii gstreamer1.0-plugins-bad-videoparsers:amd64 1.8.2-1ubuntu0.1 amd64 GStreamer videoparsers plugin from the "bad" set ii gstreamer1.0-plugins-base:amd64 1.8.2-1ubuntu0.1 amd64 GStreamer plugins from the "base" set ii gstreamer1.0-plugins-base-apps 1.8.2-1ubuntu0.1 amd64 GStreamer helper programs from the "base" set ii gstreamer1.0-plugins-good:amd64 1.8.2-1ubuntu0.1 amd64 GStreamer plugins from the "good" set ii gstreamer1.0-plugins-ugly:amd64 1.8.2-1ubuntu0.1 amd64 GStreamer plugins from the "ugly" set ii gstreamer1.0-plugins-ugly-amr:amd64 1.8.2-1ubuntu0.1 amd64 GStreamer plugins from the "ugly" set ii gstreamer1.0-pulseaudio:amd64 1.8.2-1ubuntu0.1 amd64 GStreamer plugin for PulseAudio ii gstreamer1.0-tools 1.8.2-1~ubuntu1 amd64 Tools for use with GStreamer ii gstreamer1.0-x:amd64 1.8.2-1ubuntu0.1 amd64 GStreamer plugins for X11 and Pango ii libgstreamer-plugins-bad1.0-0:amd64 1.8.2-1ubuntu0.1 amd64 GStreamer development files for libraries from the "bad" set ii libgstreamer-plugins-base1.0-0:amd64 1.8.2-1ubuntu0.1 amd64 GStreamer libraries from the "base" set ii libgstreamer-plugins-good1.0-0:amd64 1.8.2-1ubuntu0.1 amd64 GStreamer development files for libraries from the "good" set ii libgstreamer1.0-0:amd64 1.8.2-1~ubuntu1 amd64 Core GStreamer libraries and elements ii libreoffice-avmedia-backend-gstreamer 1:5.1.4-0ubuntu1 amd64 GStreamer backend for LibreOffice ii phonon-backend-gstreamer:amd64 4:4.8.2-0ubuntu2 amd64 Phonon GStreamer 1.0 backend ii phonon-backend-gstreamer-common:amd64 4:4.8.2-0ubuntu2 amd64 Phonon GStreamer 1.0.x backend icons ii phonon4qt5-backend-gstreamer:amd64 4:4.8.2-0ubuntu2 amd64 Phonon Qt5 GStreamer 1.0 backendSorry for the late reply guys! I did not realize you had replied. I just enabled email notification in my profile for this forum (they were disabled by default). I appreciate your help!
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wrote on 15 Aug 2016, 19:32 last edited by
Here is the application output in Qt Creator:
Starting /home/aras/Qt5.7.0/Examples/Qt-5.7/multimedia/build-declarative-camera-Desktop_Qt_5_7_0_GCC_64bit-Debug/declarative-camera... QML debugging is enabled. Only use this in a safe environment. defaultServiceProvider::requestService(): no service found for - "org.qt-project.qt.camera" defaultServiceProvider::requestService(): no service found for - "org.qt-project.qt.mediaplayer" qrc:///VideoCaptureControls.qml:110: Error: Cannot assign [undefined] to QString qrc:///CameraListButton.qml:65:5: QML CameraListPopup: Binding loop detected for property "currentValue" qrc:///PhotoCaptureControls.qml:135: Error: Cannot assign [undefined] to QString qrc:///CameraListButton.qml:65:5: QML CameraListPopup: Binding loop detected for property "currentValue" /home/aras/Qt5.7.0/Examples/Qt-5.7/multimedia/build-declarative-camera-Desktop_Qt_5_7_0_GCC_64bit-Debug/declarative-camera exited with code 0 -
IIRC, the gstreamer backend is built against 0.1 so one thing you could do is re-build the plugin against 1.0.
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IIRC, the gstreamer backend is built against 0.1 so one thing you could do is re-build the plugin against 1.0.
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The QtMultimedia module provides the backends. You don't need to rebuild the whole module, just the gstreamer backend.
You can grab the sources from the installer to get you started.
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wrote on 15 Aug 2016, 23:18 last edited by
I went into software repository and installed anything matching
gstreamer1.0*and then tried running the sample app again. Now the video is working. So it was a dependancy on one of the gstreamer1.0 packages. Unfortunately I dont know which one.Thank you for your help @SGaist and @jerome_isAviable !
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wrote on 17 Aug 2016, 21:36 last edited by
I am now having this exact problem on a second machine. Searching through repository for any packages related to gstreamer and installing them -- it seems so ad hoc!
Is there any way to see in Qt Creator or in the application output what library should be providing the camera service? That way I can just install that library instead of the other 200 and be sure I got it right. Any suggestions?
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I'm not 100% sure but I think it's the
gst-plugins-goodpackage. -
wrote on 22 Aug 2016, 19:01 last edited by
Thanks for the hint @SGaist ! On this new install it was the
gstreamer0.10-plugins-goodset that I was missing. I had the version1.0installed instead of0.1.I am going to mark this thread as resolved, but I still would like to know if there is a better way to figure out what library is missing. So if you know, please chime in! Thanks!
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You're welcome !
If you would like to use the latest version of gstreamer, you'll likely have to re-build the QtMultimedia backend.
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