SoftwareContext and QML Camera

ramn

Hello All,

I've compiled Qt 5.9 for a board with no hardware acceleration and we don't want to use X11. Using linuxfb QML works fine after setting these environment variables.

QT_QPA_PLATFORM=linuxfb:fb=/dev/fb0
QMLSCENE_DEVICE=softwarecontext

Now, I want to use the camera / mediaplayer. Initialising the Camera and VideoOutput QML components but nothing shows up on the screen although GStreamer claims frames are being generated (GST_DEBUG=4). Is there any environment variable needed for setting up the video surface needed by the GStreamer? Any help would be greatly appreciated...

Thanks,
Ram

SGaist

Hi,

Might be a silly question but are you sure you are getting images with content from the camera ?

ramn

Hi @SGaist

If I use QMainWindow (i.e., use widgets) along with QCamera and QCameraViewFinder, the camera works fine.
If I switch to QML application, there is nothing on the screen. Please see the GStreamer output (GST_DEBUG=4) below.

0:00:05.321409586   221   0x268600 INFO              GST_STATES gstelement.c:2419:gst_element_continue_state:<camerabin> completed state change to PLAYING
0:00:05.321595211   221   0x268600 INFO              GST_STATES gstelement.c:2324:_priv_gst_element_state_changed:<camerabin> notifying about state-changed PAUSED to PLAYING (VOID_PENDING pending)
0:00:05.322469461   221   0x1d9860 INFO                 v4l2src gstv4l2src.c:830:gst_v4l2src_create:<camera_source> sync to 0:00:00.133333332 out ts 0:00:02.032928945

0:00:05.368815919   221   0x1d9860 INFO                 v4l2src gstv4l2src.c:830:gst_v4l2src_create:<camera_source> sync to 0:00:00.166666665 out ts 0:00:02.097022611
0:00:05.369229586   221   0x1d9860 WARN                 v4l2src gstv4l2src.c:849:gst_v4l2src_create:<camera_source> lost frames detected: count = 1 - ts: 0:00:02.097022611

0:00:05.403758586   221   0x1d9860 INFO                 v4l2src gstv4l2src.c:830:gst_v4l2src_create:<camera_source> sync to 0:00:00.199999998 out ts 0:00:02.130178903
0:00:05.436278003   221   0x1d9860 INFO                 v4l2src gstv4l2src.c:830:gst_v4l2src_create:<camera_source> sync to 0:00:00.233333331 out ts 0:00:02.165139987
0:00:05.468890711   221   0x1d9860 INFO                 v4l2src gstv4l2src.c:830:gst_v4l2src_create:<camera_source> sync to 0:00:00.266666664 out ts 0:00:02.197661361
0:00:05.503736086   221   0x1d9860 INFO                 v4l2src gstv4l2src.c:830:gst_v4l2src_create:<camera_source> sync to 0:00:00.299999997 out ts 0:00:02.230155986
0:00:05.536265336   221   0x1d9860 INFO                 v4l2src gstv4l2src.c:830:gst_v4l2src_create:<camera_source> sync to 0:00:00.333333330 out ts 0:00:02.265127403
0:00:05.568742294   221   0x1d9860 INFO                 v4l2src gstv4l2src.c:830:gst_v4l2src_create:<camera_source> sync to 0:00:00.366666663 out ts 0:00:02.297644903
0:00:05.603719836   221   0x1d9860 INFO                 v4l2src gstv4l2src.c:830:gst_v4l2src_create:<camera_source> sync to 0:00:00.399999996 out ts 0:00:02.330132236
0:00:05.636222086   221   0x1d9860 INFO                 v4l2src gstv4l2src.c:830:gst_v4l2src_create:<camera_source> sync to 0:00:00.433333329 out ts 0:00:02.365100945
0:00:05.668740336   221   0x1d9860 INFO                 v4l2src gstv4l2src.c:830:gst_v4l2src_create:<camera_source> sync to 0:00:00.466666662 out ts 0:00:02.397607820

Thanks again.

SGaist

If you start your widget application after your QML application, does it work correctly ?

ramn

@SGaist

Sorry for the delayed reply. I don't need to run both the applications. I'm evaluating software rendering and is not working with QML multimedia.

Thanks for your help!

SGaist

Are you thinking about using the Qt Quick 2D renderer ?

dzawisko

@SGaist

Hi SGaist,

You asked:
"Might be a silly question but are you sure you are getting images with content from the camera ?"

I have got that problem with the QML Camera.

I can make images and show images on the screen but I cannot see a video stream in the VideoOutput.
The camera's LED lights like during normal work.

Best Regards
Darek

SGaist

Hi,

Please give more information about your setup.

Qt version
OS version
Camera type
etc.

dzawisko

@SGaist

i.MX6ull
Yocto Rocko with a framebuffer
export DISPLAY=:0
export QMLSCENE_DEVICE=softwarecontext
export QT_QPA_PLATFORM=linuxfb
Qt 5.9.2
2 different type of the USB Camera (UVC) from Logitech

I have got a video output when I am using GStreamer from the command line, for example:
gst-launch-1.0 v4l2src device=/dev/video1 ! imxpxpvideosink

The problem is that I cannot use a GStreamer separate because the imxpxpvideosink doesn't have an overlay feature.
In that case, I have to use a QML Camera inside the Qt application.

Best Regards
Darek

SGaist

Depending on what you need the QtGstreamer module might be interest.

dzawisko

Thank you for your help.
I will check it.

Darek