cv_video_helper.hxx

#pragma once

#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>

namespace
{
  struct cv_video_helper_t final
  {
    using frames_t = std::vector<cv::Mat>;
    using frames_fps_t = std::tuple<frames_t, int>;
    
    static frames_fps_t load_to_vector(const std::string& video_filename)
    {
      auto video = cv::VideoCapture(video_filename);
      
      if(!video.isOpened())
        throw std::runtime_error("cannot open video file.");
      
      const int fps = int(video.get(CV_CAP_PROP_FPS));
      
      const size_t frame_count = video.get(CV_CAP_PROP_FRAME_COUNT);
      if(frame_count == 0)
        throw std::runtime_error("cannot get frame count");
      
      frames_t frames(frame_count);
      
      for(auto& frame : frames)
      {
        cv::Mat source;
        video >> source;
        source.copyTo(frame);
      }
      
      return make_tuple(std::move(frames), std::move(fps));
    }
    
  private:
    cv_video_helper_t();
  };
}

test.cxx

#include <iostream>

#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>

#include "cv_video_helper.hxx"

int main(int n, char** a)
{
  if(n < 1)
    throw;
  // write test
  {
    const auto frames_fps = cv_video_helper_t::load_to_vector(a[1]);
    const auto& frames = std::get<0>(frames_fps);
    const auto& fps    = std::get<1>(frames_fps);
    
    {
      cv::VideoWriter writer("test.avi", CV_FOURCC('X','V','I','D'), fps, cv::Size(frames.at(0).cols, frames.at(0).rows));
      
      for(const auto& frame : frames)
        writer << frame;
    }
  }
  
  // read test
  {
    const auto frames_fps = cv_video_helper_t::load_to_vector("test.avi");
    const auto& frames = std::get<0>(frames_fps);
    const auto& fps    = std::get<1>(frames_fps);
    
    std::cout << "      first frame width : " << frames.at(0).cols << " [px]\n"
              << "                  height: " << frames.at(0).rows << " [px]\n"
              << "      fps               : " << fps << " [fps]\n"
              << "      frame count       : " << frames.size() << " [#]\n"
              << "      time              : " << frames.size() / fps << " [sec]\n"
              ;
  }
}