CameraRecorder without audio

  • Hi,

    in my app running on embedded target (iMX6) I need to record videos. I am trying to use the QML CameraRecorder (using the videoRecorder property of Camera). The problem I am facing is, that the camera output is slowed down extremely as soon as I enable the videoRecorder. On the console I can see the error CameraBin warning: "Can't record audio fast enough" (which is comming from gstreamer. As I don't need any audio recorded in the video at all, I am looking for a way to set things up so that I can record only the video without any audio. I have searched for a solution for 2 days now and I couldn't find any answer. So maybe someone here on the forum can help out.

    Thx, YenZi

  • So, I just found out that this gstreamer pipeline on the commandline works just fine and records the camera capture to a file :

    gst-launch-1.0 -e imxv4l2videosrc ! imxvpuenc_h264 bitrate=4096 ! h264parse ! mp4mux ! filesink location=video.mp4

    Now the question would be, how I can control these gstreamer pipeline params just by using the QML Camera component ?

  • Qt Champions 2018

    Have you tried setting the muted property of your CameraRecorder to true ?

  • @GrecKo it's right, see.

    Camera Recorder QML

    Cleiton Bueno

    Blog | Linkedin | B2Open

  • Hi @GrecKo ,

    yes, I've set muted: true. Makes no difference.

  • Hi @Cleiton-Bueno,

    even if I set muted: true the gstreamer pipeline still seems to have audio encoding included. The biggest problem is, that I don't have control over the gstreamer pipeline working as the backend for QtMultimedia elements.

  • @YenZi An alternative so you do not have to change QtMultimedia source-code, create patches and everything else is to block the kernel module regarding the mic part of the webcam, for example:

    Listing the drivers/modules for the audio interfaces:

    $ cat /proc/asound/modules
      0 snd_hda_intel

    Then add in the blacklist this module, be careful that more than one can identify the WebCamera/Camera:

    # echo "blacklist snd_hda_intel" >> /etc/modprobe.d/blacklist.conf

    So the module will not load and the capture will not work.

    Cleiton Bueno

    Blog | Linkedin | B2Open

  • @Cleiton-Bueno thanks for your suggestion. I have disabled audio in my kernel completely now. Now I get the message CameraBin warning: "Could not open audio device for recording." which shows, that I really removed audio support.
    Unfortunately, this still doesn't solve my basic issue, which is a extremely sluggish video output when the videoRecorder property is enabled in the Camera. That means, the audio encoding was not causing this problem at all.

    Thx, Jens

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