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;
}