samples/cpp/videowriter.cpp

An example using VideoCapture and VideoWriter class

 
#include <opencv2/core.hpp>
#include <opencv2/videoio.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/imgproc.hpp>
#include <iostream>
#include <map>
 
using namespace cv;
using namespace std;
 
inline map<string, int> fourccByCodec() {
    map<string, int> res;
    res["h264"] = VideoWriter::fourcc('H', '2', '6', '4');
    res["h265"] = VideoWriter::fourcc('H', 'E', 'V', 'C');
    res["mpeg2"] = VideoWriter::fourcc('M', 'P', 'E', 'G');
    res["mpeg4"] = VideoWriter::fourcc('M', 'P', '4', '2');
    res["mjpeg"] = VideoWriter::fourcc('M', 'J', 'P', 'G');
    res["vp8"] = VideoWriter::fourcc('V', 'P', '8', '0');
    return res;
}
 
// Function to parse resolution string "WxH"
static Size parseResolution(const string& resolution) {
    stringstream ss(resolution);
    int width, height;
    char delimiter;
 
    ss >> width >> delimiter >> height;
 
    if (ss.fail() || delimiter != 'x') {
        throw runtime_error("Invalid resolution format. Please provide in WxH format.");
    }
 
    return Size(width, height);
}
 
 
int main(int argc, char** argv) {
    const String keys =
        "{help h usage ? |      | Print help message   }"
        "{fps           |30    | fix frame per second for encoding (supported: fps > 0)   }"
        "{codec         |mjpeg | Supported codecs depend on OpenCV Configuration. Try one of 'h264', 'h265', 'mpeg2', 'mpeg4', 'mjpeg', 'vp8' }"
        "{resolution    |1280x720 | Video resolution in WxH format, (e.g., '1920x1080') }"
        "{output_filepath    | output.avi | Path to the output video file}";
 
    CommandLineParser parser(argc, argv, keys);
    parser.about("Video Capture and Write with codec and resolution options");
 
    if (parser.has("help")) {
        parser.printMessage();
        return 0;
    }
 
    double fps = parser.get<double>("fps");
    string codecStr = parser.get<string>("codec");
    string resolutionStr = parser.get<string>("resolution");
    string outputFilepath = parser.get<string>("output_filepath");
 
    auto codecMap = fourccByCodec();
 
    if (codecMap.find(codecStr) == codecMap.end()) {
        cerr << "Invalid codec" << endl;
        return -1;
    }
 
    int codec = codecMap[codecStr];
    Size resolution = parseResolution(resolutionStr);
 
    // Video Capture
    VideoCapture cap(0);
    if (!cap.isOpened()) {
        cerr << "ERROR! Unable to open camera\n";
        return -1;
    }
 
    cout << "Selected FPS: " << fps << endl;
    cout << "Selected Codec: " << codecStr << endl;
    cout << "Selected Resolution: " << resolutionStr << " (" << resolution.width << "x" << resolution.height << ")" << endl;
 
    // Set up VideoWriter
    VideoWriter writer(outputFilepath, codec, fps, resolution, true); // Assuming color video
    if (!writer.isOpened()) {
        cerr << "Could not open the output video file for write\n";
        return -1;
    }
 
    cout << "Writing video file: " << outputFilepath << endl
         << "Press any key to terminate" << endl;
 
    Mat frame, resizedFrame;
    for (;;) {
        // Capture frame
        if (!cap.read(frame) || frame.empty()) {
            break;
        }
 
        // Resize frame to desired resolution
        resize(frame, resizedFrame, resolution);
 
        // Write resized frame to video
        writer.write(resizedFrame);
 
        // Show live
        imshow("Live", resizedFrame);
        if (waitKey(5) >= 0) break;
    }
 
    // VideoWriter and VideoCapture are automatically closed by their destructors
 
    return 0;
}