Timelapse using opencv 4.0 and c/c++

timelapse.cpp

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

int main()
{
	cv::VideoCapture cap("water.mp4");

	if (!cap.isOpened())
	{
		std::cerr << "Cannot open video file. Check file path!\n";

		return -1;
	}

	// required parameters of the current video file
	// get video file fps, total frames, video codec(fourcc) and frame size
	double fps = cap.get(cv::CAP_PROP_FPS);
	long int maxframes = (long int)cap.get(cv::CAP_PROP_FRAME_COUNT);
	int fourCC = (int)cap.get(cv::CAP_PROP_FOURCC);
	cv::Size framesz = cv::Size((int)cap.get(cv::CAP_PROP_FRAME_WIDTH), (int)cap.get(cv::CAP_PROP_FRAME_HEIGHT));
	
	// set output video parameters
	int outputFPS = 60;
	int numOfFramesToSkip = 5;
	std::string saveFileName = "water_tl.mp4";

	//std::cout << "FPS of actual video is: " << fps << "\n";

	long int counter = 0;

	cv::Mat img;
	cap.read(img);

	// object of videowriter class to create a video from individual frames 
	cv::VideoWriter vidwriter;

	if (img.channels() == 3) // bgr
		vidwriter = cv::VideoWriter(saveFileName, cv::VideoWriter::fourcc('M', 'P', '4', 'V'), outputFPS, framesz, true);
	else // gray scale
		vidwriter = cv::VideoWriter(saveFileName, cv::VideoWriter::fourcc('M', 'P', '4', 'V'), outputFPS, framesz, false);

	cv::Mat frame;

	while (true)
	{
		cap >> frame;

		// if frame exists, write to video
		if (!frame.empty())
		{
			if (counter % numOfFramesToSkip == 0)
			{
				vidwriter.write(frame);
			}
		}
		else
			return 0;

		counter++;
	}
}