| OpenCV 5.0.0alpha Open Source Computer Vision

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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;
}
cv::CommandLineParser
Designed for command line parsing.
Definition utility.hpp:890
cv::Mat
n-dimensional dense array class
Definition mat.hpp:951
cv::Mat::empty
bool empty() const
Returns true if the array has no elements.
cv::Size_
Template class for specifying the size of an image or rectangle.
Definition types.hpp:338
cv::Size_::height
_Tp height
the height
Definition types.hpp:366
cv::Size_::width
_Tp width
the width
Definition types.hpp:365
cv::VideoCapture
Class for video capturing from video files, image sequences or cameras.
Definition videoio.hpp:727
cv::VideoWriter
Video writer class.
Definition videoio.hpp:994
cv::String
std::string String
Definition cvstd.hpp:151
cv::imshow
void imshow(const String &winname, InputArray mat)
Displays an image in the specified window.
cv::waitKey
int waitKey(int delay=0)
Waits for a pressed key.
cv::resize
void resize(InputArray src, OutputArray dst, Size dsize, double fx=0, double fy=0, int interpolation=INTER_LINEAR)
Resizes an image.
highgui.hpp
main
int main(int argc, char *argv[])
Definition highgui_qt.cpp:3
core.hpp
imgproc.hpp
cv
Definition core.hpp:107
std
STL namespace.
videoio.hpp