dlib C++ Library - ffmpeg_video_decoding2_ex.cpp

    // 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 decoding API.

        This is a pretty simple example. It loads a raw codec file, parses chunks of
        data to the decoder, plots images to a GUI window, and counts audio samples.
    */

    #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 encoded stream. e.g. dlib/test/ffmpeg_data/MOT20-08-raw.h264", 1);
        parser.add_option("codec",  "codec name. e.g. h264", 1);
        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();
        const std::string codec    = parser.option("codec").argument();

        decoder dec([&] {
            decoder::args args;
            args.codec_name = codec;
            return args;
        }());

        if (!dec.is_open())
        {
            printf("Failed to create decoder.\n");
            return EXIT_FAILURE;
        }

        frame                   f;
        array2d<rgb_pixel>      img;
        int                     samples{0};
        image_window            win;

        // 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 wrap() which either resizes or resamples
        // 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};

        const auto callback = [&](frame& f)
        {
            if (f.is_image())
            {
                convert(f, img);
                win.set_image(img);
            }
            else if (f.is_audio())
            {
                samples += f.nsamples();
            }
        };

        ifstream fin{filepath, std::ios::binary};
        std::vector<char> buf(1024);

        while (fin)
        {
            fin.read(buf.data(), buf.size());
            size_t ret = fin.gcount();
            dec.push((const uint8_t*)buf.data(), ret, wrap(callback, args_image));
        }

        dec.flush(wrap(callback, args_image));

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

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