OpenCV C++ Program to play a video - GeeksforGeeks

09 Feb, 2018
The following is the explanation to the C++ code to play a video in C++ using the tool OpenCV.Things to know:(1) The code will only compile in Linux environment.(2) To run in windows, please use the file: ‘play_video.o’ and run it in cmd. However if it does not run(problem in system architecture) then compile it inwindows by making suitable and obvious changes to the code like: Use<iostream.h> in place of <iostream>.(3) Compile command: g++ -w vid.cpp -o vid `pkg-config –libs opencv`(4) Run command: ./vid(5) Please make sure that the video : “Bumpy.mp4” is in the same location.Before you run the code, please make sure that you have OpenCV installed on your system.Code Snippet:
#include "opencv2/highgui/highgui.hpp"
// highgui - an interface to video and image capturing.

#include 
// The header files for performing input and output.

using namespace cv;
// Namespace where all the C++ OpenCV functionality resides.

using namespace std;
// For input output operations.


int main()
{
    VideoCapture cap("Bumpy.mp4");
    // cap is the object of class video capture that tries to capture Bumpy.mp4
    if ( !cap.isOpened() )  // isOpened() returns true if capturing has been initialized.
    {
        cout << "Cannot open the video file. \n";
        return -1;
    }

    double fps = cap.get(CV_CAP_PROP_FPS); //get the frames per seconds of the video
    // The function get is used to derive a property from the element.
    // Example:
    // CV_CAP_PROP_POS_MSEC :  Current Video capture timestamp.
    // CV_CAP_PROP_POS_FRAMES : Index of the next frame.

    namedWindow("A_good_name",CV_WINDOW_AUTOSIZE); //create a window called "MyVideo"
    // first argument: name of the window.
    // second argument: flag- types: 
    // WINDOW_NORMAL : The user can resize the window.
    // WINDOW_AUTOSIZE : The window size is automatically adjusted to fitvthe displayed image() ), and you cannot change the window size manually.
    // WINDOW_OPENGL : The window will be created with OpenGL support.

    while(1)
    {
        Mat frame;
        // Mat object is a basic image container. frame is an object of Mat.

        if (!cap.read(frame)) // if not success, break loop
        // read() decodes and captures the next frame.
        {
            cout<<"\n Cannot read the video file. \n";
            break;
        }

        imshow("A_good_name", frame);
        // first argument: name of the window.
        // second argument: image to be shown(Mat object).

        if(waitKey(30) == 27) // Wait for 'esc' key press to exit
        { 
            break; 
        }
    }

    return 0;
}
// END OF PROGRAM
About the Author: 
Aditya Prakash is an undergraduate student at Indian Institute of Information Technology, Vadodara. He primarily codes in C++. The motto for him is: So far so good. He plays cricket, watches superhero movies, football and is a big fan of answering questions.
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