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QCamera is not working with CMOS-MIPI-OV5640

  • Hi,

    I am having iMX6 development kit with CMOS-MIPI-OV5640. Kit is having Debian Stretch 9.5.

    At present, I am trying to play live stream using QT (QCamera functionality). I have developed sample code for that and it is working fine with laptop(ubuntu 16.04) and it's webcam.
    But on IMX6 development kit, on the execution of QCamera->start(), the QT application hangs.

    Please find code related to camera:
    QCamera *pCamera;
    //Find Camera
    QList<QCameraInfo> cameras = QCameraInfo::availableCameras();
    foreach (const QCameraInfo &cameraInfo, cameras){
    pCamera = new QCamera(cameraInfo, this); //gives cameraInfo.deviceName() = "/dev/video0"
    pCameraViewfinder = new QCameraViewfinder(this);
    pCameraImageCapture = new QCameraImageCapture(pCamera, this);
    pVBoxLayout = new QVBoxLayout();

    //Set Camera View

    // Start Camera
    pCamera→start(); //Hangs at this line, not able to do anything on UI and gives an error.

    Looking forward to hearing.

    Thank You,
    Nikita Panchal

  • Lifetime Qt Champion

    Hi and welcome to devnet,

    Can you access that camera properly from gstreamer ?

  • Yes.

    I am able to get live stream with :
    gst-launch-1.0 imxv4l2videosrc device=/dev/video0 ! imxeglvivsink

  • Lifetime Qt Champion

    Do you have any error printed on the command line when running your Qt application ?

  • Hi Devent,

    First of thank you for looking into it.
    Qt application itself doesn't print any error on console.

    While analyze the problem I identified two things as below:

    1. Difference between Camera Start method on laptop and IMX6.
      On laptop: pCamera->start() followes status: LoadingStatus -> LoadedStatus -> StartingStatus -> ActiveStatus.
      On IMX6 : pCamera->start() followes status: LoadingStatus
      So, It is stuck to change status from "LoadingStatus" to "LoadedStatus".

    2. I got below error with dmesg command:
      pid: 1170
      uid: [ 1001]
      tgid: 1170
      rss: 150081
      nr_ptes: 405
      nr_pmds: 0
      swapents: 0
      oom_score_adj: 0
      name: CameraStartApp
      Out of memory: Kill process 1170 (CameraStartApp) score 587 or sacrifice child
      Killed process 1170 (CameraStartApp) total-vm:881416kB, anon-rss:599680kB, file-rss:0kB, shmem-rss:644kB

  • Lifetime Qt Champion

    Looks like a device specific source

    @nikita.panchal09 said in QCamera is not working with CMOS-MIPI-OV5640:


    You should consider modifying the gstreamer plugin to use that one in place of the camerabin it currently uses.

  • Hi,

    Thank you for your answer.
    Actually, I am new to GStreamer and qtmultimedia. I would be grateful, if you can provide steps or related website-link to do these things.

    Meanwhile, I found the hardcoded value of camera source as "v4l2src" in below files from QT source. Do these both files requires to change to "imxv4l2videosrc" from "v4l2src" and build it again?

    1. qtmultimedia-5.12/src/plugins/gstreamer/mediacapture/qgstreamerv4l2input.cpp:70: GstElement *camera = gst_element_factory_make("v4l2src", "camera_source");
    2. qtmultimedia-5.12/src/plugins/gstreamer/camerabin/camerabinsession.cpp:542: m_videoSrc = gst_element_factory_make("v4l2src", "camera_source");


  • Lifetime Qt Champion

    That's what I would try first yes. No need to rebuild all of Qt. Only the GStreamer plugin.

  • Hi,

    I followed below steps:

    • Downloaded qt-multimedia
    • Edited mentioned files with "imxv4l2videosrc"
    • Compiled and Installed.

    It works...! I am able to start the camera.

    Thank you

  • Hi,

    Currently, I am trying to record video on IMX6(Debian Stretch 9.5). I am using QT multimediawidget "camera" example (Using QCamera and QMediaRecorder).
    The problem is, On record start (recorder->record) the camera output is slowed down extremely. and after approximate 15 seconds, It gives below error and streaming gets stopped.
    "CameraBin error: "Internal data stream error."

    I am able to record video with gstreamer using below command and it works fine.
    gst-launch-1.0 imxv4l2videosrc device=/dev/video0 imx-capture-mode=5 fps-n=30 ! queue ! imxvpuenc_h264 bitrate=10000 ! avimux ! filesink location=test.avi

    Looking forward to hearing.

    Thank You.

  • Lifetime Qt Champion

    From the looks of it, imxvpuenc_h264 is likely optimised for your device. I would go check the qgstreamercapturesession.cpp content to see how to possibly modify the pipeline to use that encoder.

  • Hi,

    Thanks for your answer.

    While analyzing the problem I found below things as per below:

    1. In the computer, it saves video file as .mkv and in the board, It saves as .ogg
    2. After camera record start it gives error as "CameraBin error: "Internal data stream error."
      simultaneously on the console, I am getting "ERROR: v4l2 capture: mxc_v4l_dqueue timeout enc_counter 0" error.
    3. As per your saying I have to write codec "imxvpuenc_h264". But I am confused that where to change it.
      I have changed "x264enc" to "imxvpuenc_h264" in file qgstreamervideoencode.cpp. But, while recording It is not executing.

    Nikita Panchal

  • Lifetime Qt Champion

    What do you mean by "not executing" ?

  • I have put "qDebug()" on it. It doesn't print on recording start.

  • Lifetime Qt Champion

    Maybe a silly question but are you sure you replaced the plugin once you built it ?

  • Hi,

    I have applied "0001-QCamera-can-t-set-recording-container-format-video-a.patch" patch from below link and it works for me.
    Thanks for your support.

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