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  1. Qt
  2. QTBUG-126277

V4L2 loopback camera has warped colors

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Details

    • Bug
    • Resolution: Unresolved
    • P2: Important
    • None
    • 6.7.1
    • Multimedia
    • None
    • Linux/X11
    • Multimedia, weeks 15-16, Multimedia, weeks 18-19

    Description

      When using V4L2 loopback to create a capture device with yuv420p pixel format, the video frame colors are skewed.

      Steps to reproduce:

      1. Create a loopback capture device with the v4l2loopback kernel module: sudo modprobe v4l2loopback video_nr5
      2. Play test stream over loopback device using ffmpeg: ffmpeg -re -f lavfi -i testsrc -vf format=yuv420p -f v4l2 /dev/video5
      3. Preview loopback camera using the declarative-camera or camera examples

      Expected

      • Test video is shown as normal

      Actual

      • Video brightness (Y-plane) is shown normally with colors (UV) being warped.
      • Using ffplay or VLC for preview shows correct colors

      Attachments

        1. umbrellas.jpg_yuv420p_bt709_full.png
          40 kB
          Mikko Hallamaa
        2. umbrellas.jpg_yuv420p_bt709_full_actual.png
          35 kB
          Mikko Hallamaa
        3. umbrellas.jpg_yuv420p_bt709_full_diff.png
          26 kB
          Mikko Hallamaa
        4. umbrellas.jpg_imc1_bt709_video.png
          40 kB
          Mikko Hallamaa
        5. umbrellas.jpg_imc1_bt709_video_actual.png
          38 kB
          Mikko Hallamaa
        6. umbrellas.jpg_imc1_bt709_video_diff.png
          36 kB
          Mikko Hallamaa

        Issue Links

          relates to

          Bug - A problem which impairs or prevents the functions of the product. QTBUG-134196 R16 video texture formats don't have a working fallback for GLES 2.0

          • P2: Important - Urgent, should be fixed, but will not stop the release.
          • In Progress
          For Gerrit Dashboard: QTBUG-126277
          # Subject Branch Project Status CR V
          640116,7 QVideoFrame: Fix calculation of UV line stride dev qt/qtmultimedia Status: NEW 0 -1

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            People

              mikko.hallamaa Mikko Hallamaa
              mikko.hallamaa Mikko Hallamaa
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              Dates

                Created:
                Updated:

                Gerrit Reviews

                  There is 1 open Gerrit change