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These samples demonstrate how to integrate NVIDIA accelerated GStreamer
plugins with the custom OpenCV software library to acquire frames for
computation.

-------------------------------------------------------------------------------
Sample-wise contents:

- opencv_camera:
    opencv_gst_camera.cpp-  File for GStreamer nvarguscamerasrc plugin use case
                        to use CSI camera for capture.
- opencv_decoder:
    opencv_gst_decoder.cpp- File for GStreamer nvv4l2decoder plugin use case
                        to decode an H264 mp4 file.
- opencv_encoder:
    opencv_gst_encoder.cpp- The file opens a CSI nvarguscamerasrc camera pipeline
                        for capture and encoding to an H264 mp4 file.

-------------------------------------------------------------------------------
Prerequisites:

The development environment must include GStreamer libraries and OpenCV 3.3.1
installed through JetPack.

- GStreamer
    Installation command:

        sudo apt-get install libgstreamer1.0-0 gstreamer1.0-plugins-base \
        gstreamer1.0-libav gstreamer1.0-plugins-good gstreamer1.0-plugins-bad \
        gstreamer1.0-plugins-ugly gstreamer1.0-tools gstreamer1.0-alsa

- OpenCV 3.3.1
    JetPack builds OpenCV with GStreamer enabled. To verify GStreamer support,
    run on python shell:

        >>> import cv2
        >>> print (cv2.getBuildInformation())

    GStreamer flags should be enabled in the output.

        >>>
        General configuration for OpenCV 3.3.1 ================================
          Version control:               3.3.1-2-g31ccdfe11

          Platform:
            Timestamp:                   2019-02-06T09:45:58Z
            Host:                        Linux 4.9.140-tegra aarch64
            CMake:                       2.8.12.2
            CMake generator:             Unix Makefiles
            CMake build tool:            /usr/bin/make
            Configuration:               Release
          ...
          ...
          ...

          Video I/O:
            DC1394 1.x:                  NO
            DC1394 2.x:                  NO
            FFMPEG:                      YES
              avcodec:                   YES (ver 57.107.100)
              avformat:                  YES (ver 57.83.100)
              avutil:                    YES (ver 55.78.100)
              swscale:                   YES (ver 4.8.100)
              avresample:                NO
            GStreamer:
              base:                      YES (ver 1.14.1)
              video:                     YES (ver 1.14.1)
              app:                       YES (ver 1.14.1)
              riff:                      YES (ver 1.14.1)
              pbutils:                   YES (ver 1.14.1)
            OpenNI:                      NO
          ...
          ...
          ...
          Install path:                  /usr

          cvconfig.h is in:              /tmp/build_opencv/build

-------------------------------------------------------------------------------
Compliation:

Each sample directory contains a makefile to build the respective application.
The command is:

    cd opencv-sample-apps/[SAMPLE_DIR]
    make

    Example:
        $ cd opencv-sample-apps/opencv_camera
        $ make

-------------------------------------------------------------------------------
Execution:

To run each sample:

- opencv_camera:
    $ ./opencv_nvgstcam [--Options]
        --h help            : Use case help
        --width             : capture width
        --height            : capture height
        --fps               : Frames per second
    Example:
        $ ./opencv_nvgstcam --width=1920 --height=1080 --fps=30

- opencv_decoder:
    $ ./opencv_nvgstdec [--Options]
        --help -h           : Use case help
        --file-path         : Absolute path of file to be decoded
        --show-fps          : Display number of frames decoded per second
                            from GStreamer pipeline
    Example:
        $ ./opencv_nvgstdec --file-path=[_FILEPATH_]

-opencv_encoder
    $ ./opencv_nvgstenc [--Options]
        --h help            : Use case help
        --width             : capture width
        --height            : capture height
        --fps               : Frames per second
        --filename          : Target H264 encoded filename
        --time              : Duration for capture in seconds
    Example:
        $ ./opencv_nvgstenc --width=1920 --height=1080 --fps=30 --time=60
            --filename= test_h264_1080p_30fps.mp4