    // The contents of this file are in the public domain. See LICENSE_FOR_EXAMPLE_PROGRAMS.txt
    /*

        This is an example illustrating the use of the ffmpeg wrappers,
        in this case the demuxer API.

        In this example, we show how to read both images and audio.
    */

    #include <cstdio>
    #include <dlib/media.h>
    #include <dlib/gui_widgets.h>
    #include <dlib/cmd_line_parser.h>

    using namespace std;
    using namespace dlib;
    using namespace dlib::ffmpeg;

    int main(const int argc, const char** argv)
    try
    {
        command_line_parser parser;
        parser.add_option("i",       "input video", 1);
        parser.add_option("verbose", "enable all internal ffmpeg logging");
        parser.set_group_name("Help Options");
        parser.add_option("h",       "alias of --help");
        parser.add_option("help",    "display this message and exit");

        parser.parse(argc, argv);
        const char* one_time_opts[] = {"i"};
        parser.check_one_time_options(one_time_opts);

        if (parser.option("h") || parser.option("help"))
        {
            parser.print_options();
            return 0;
        }

        const std::string filepath = parser.option("i").argument();

        // We use the most simple constructor, the one that takes in filepath.
        // By default, both images and audio are read.
        demuxer cap(filepath);
        if (!cap.is_open())
        {
            printf("%s is not a valid video file\n", filepath.c_str());
            return EXIT_FAILURE;
        }

        // Read images and audio.
        // Images are plotted, audio samples are counted.
        frame               f;
        array2d<rgb_pixel>  img;
        image_window        win;
        int                 nsamples{0};

        // When reading frames, we get exactly what's in the codec by default.
        // To resize, change pixel format, resample or change sample format,
        // you have to pass extra arguments to read() which either resize or resample
        // the frame. Since we want rgb_pixel, we need to set the pixel format appropriately.
        const resizing_args args_image {0, 0, pix_traits<rgb_pixel>::fmt};

        while (cap.read(f, args_image))
        {
            if (f.is_image())
            {
                convert(f, img);
                win.set_image(img);
            }
            else if (f.is_audio())
            {
                nsamples += f.nsamples();
            }
        }

        printf("Read %i audio samples\n", nsamples);

        return EXIT_SUCCESS;
    }
    catch (const std::exception& e)
    {
        printf("%s\n", e.what());
        return EXIT_FAILURE;
    }