v4l2 (Color Spaces in Video)

[mxochicale]

Streamed video to your host computer is in the format RGBA32 for V4L2VideoCaptureOp in holoscan-sdk [1], meaning that video has four channels stored in 32 bits [2]. So, you might need to drop alpha channels to match the usual three channel input and this can be done definitng your destination data type e.g. "rgb888" or "rgba8888") [3]. Maybe you would to refresh your memory on color space, chroma subsampling, bit depth and more [4]

[1] https://github.com/nvidia-holoscan/holoscan-sdk/blob/main/python/holoscan/operators/v4l2_video_capture/pydoc.hpp
[2] https://en.wikipedia.org/wiki/RGBA_color_model
[3] https://github.com/nvidia-holoscan/holoscan-sdk/blob/main/python/holoscan/operators/format_converter/pydoc.hpp
[4] https://video.matrox.com/en/media/guides-articles/introduction-color-spaces-video

extras

• [Multimedia] GPU processing of V4L2 live video on NVIDIA Jetson with CUDA https://www.youtube.com/watch?app=desktop&v=EV3DafjteBQ
  • https://www.kernel.org/doc/html/v5.8/admin-guide/media/vimc.html
  • https://www.kernel.org/doc/html/v5.8/driver-api/media/v4l2-core.html
  • https://docs.nvidia.com/jetson/archives/l4t-archived/l4t-3242/index.html#page/Tegra%20Linux%20Driver%20Package%20Development%20Guide/camera_sensor_prog.html
• https://github.com/severin-lemaignan/webcam-v4l2
• https://github.com/narfster/v4l2cxx
• libv4l2cpp C++ wrapper for V4L2 https://github.com/mpromonet/libv4l2cpp
  • https://github.com/lagadic/visp/blob/master/tutorial/grabber/tutorial-grabber-v4l2-threaded.cpp
• https://www.youtube.com/user/VispTeam/videos
• https://arcoresearchgroup.wordpress.com/2020/06/02/virtual-camera-for-opencv-using-v4l2loopback/
• https://bitbucket.org/OscarAcena/ocv-virtual-cam/src/master/
• https://www.linuxtv.org/wiki/index.php/V4L2_Userspace_Library
• https://stackoverflow.com/questions/62528583/capture-image-with-v4l2-on-jetson-tx2
  • https://elixir.bootlin.com/linux/v4.9.237/source/include/uapi/linux/videodev2.h#L499
  • https://elixir.bootlin.com/linux/v6.9-rc1/source/include/uapi/linux/videodev2.h
• https://lightbits.github.io/v4l2_real_time/
• https://github.com/pyrovski/h264-v4l2-capture/tree/master
• ..