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