Writing Video to File with OpenCV - c++

Question

Hi im trying to write a video from my webcam to my computer but I keep getting the error that my writer isnt opened. Im using windows 8 64 bit, VS 2013 & OpenCV 2.4.10. Here is the code that I am using:
#include <opencv\highgui.h>
#include <opencv\cv.h>
#include <iostream>
using namespace cv;
using namespace std;
string intToString(int number){
std::stringstream ss;
ss << number;
return ss.str();
}
int main(int argc, char* argv[])
{
VideoCapture cap(0); // open the video camera no. 0
VideoWriter writer;
if (!cap.isOpened()) // if not success, exit program
{
cout << "ERROR INITIALIZING VIDEO CAPTURE" << endl;
return -1;
}
char* windowName = "Webcam Feed";
namedWindow(windowName, CV_WINDOW_AUTOSIZE); //create a window to display our webcam feed
string filename = "C:\\thevideo.avi";
int fcc = CV_FOURCC('D', 'I', 'V', '3');
double fps = 20;
cv::Size frameSize(cap.get(CV_CAP_PROP_FRAME_WIDTH), cap.get(CV_CAP_PROP_FRAME_HEIGHT));
writer = VideoWriter(filename, fcc, fps, frameSize);
if (!writer.isOpened())
{
cout << "the writer isnt opened" << endl;
getchar();
return -1;
}
while (1) {
Mat frame;
bool bSuccess = cap.read(frame); // read a new frame from camera feed
if (!bSuccess) //test if frame successfully read
{
cout << "ERROR READING FRAME FROM CAMERA FEED" << endl;
break;
}
writer.write(frame);
imshow(windowName, frame); //show the frame in "MyVideo" window
//listen for 10ms for a key to be pressed
switch (waitKey(10)){
case 27:
//'esc' has been pressed (ASCII value for 'esc' is 27)
//exit program.
return 0;
}
}
return 0;
}
Can anyone help me?

Answer 1

I find the use a bit confusing. You do:
VideoWriter writer;
and then
writer = VideoWriter(filename, fcc, fps, frameSize);
Either do:
VideoWriter writer = VideoWriter(filename, fcc, fps, frameSize);
or
VideoWriter writer;
writer.open(filename, 0, fps, frameSize, 1);
Perhaps that is the issue?
Also, in writer.open(), the last parameter sis the colour setting. Set it accordingly. I have assumed you have colour input.
Also, a more complicated thing could be codec issue. I read that OPENCV can only write AVI files. So, I am not sure if it can use the DIV3 codec for writing. Call the writer with:
writer = VideoWriter(filename, -1, fps, frameSize);
and see what codecs can be used.

Answer 2

Try this codec:
int fcc = CV_FOURCC('M', 'J', 'P', 'G')
instead of:
int fcc = CV_FOURCC('D', 'I', 'V', '3');