Reading a video with openCV

Question

I have a video engine2.avi that I want to read and show with openCV. Here\'s my code:

#include 
#include 

        

Answer 1

If you are just looking out for displaying the video, here's the code that worked for me, Please check if it helps you in any way.

#include <stdio.h>
#include <opencv2/opencv.hpp>
int main(){
CvCapture *camera=cvCaptureFromFile("C:\\test.avi");
if (camera==NULL)
    printf("camera is null\n");
else
    printf("camera is not null");

cvNamedWindow("img");
while (cvWaitKey(10)!=atoi("q")){
    double t1=(double)cvGetTickCount();
    IplImage *img=cvQueryFrame(camera);
    /*if(img){
        cvSaveImage("C:/opencv.jpg",img);
    }*/
    double t2=(double)cvGetTickCount();
    printf("time: %gms  fps: %.2g\n",(t2-t1)/(cvGetTickFrequency()*1000.), 1000./((t2-t1)/(cvGetTickFrequency()*1000.)));
    cvShowImage("img",img);
}
cvReleaseCapture(&camera);
}

Hope this helps you.

Answer 2

Here is a couple of links that might help you:

• Load, Save and Show YUV 420 images
• How to read a frame from YUV file in OpenCV?
• Converting YUV into BGR or RGB in OpenCV

Edit:

I must clear something first: OpenCV is capable of reading YUV frames from a video file because it's the underlying library (FFmpeg/GStreamer) that does the job. OpenCV also supports converting between a specific type of YUV and RGB through cvCvtColor() with CV_YCrCb2RGB or CV_RGBYCrCb.

Upon examining your question again, I noticed you didn't specify the kind of error that happened. You could do a better job at dealing with a possible failure from the capture interface by printing a message to the screen instead of throwing it.

I tested the video file you shared and I had no problems playing it on a window using the following code:

#include <cv.h>
#include <highgui.h>

#include <iostream>

int main(int argc, char* argv[])
{
    cv::VideoCapture cap(argv[1]);
    if (!cap.isOpened())
    {
        std::cout << "!!! Failed to open file: " << argv[1] << std::endl;
        return -1;
    }

    cv::Mat frame;
    for(;;)
    {

        if (!cap.read(frame))             
            break;

        cv::imshow("window", frame);

        char key = cvWaitKey(10);
        if (key == 27) // ESC
            break;
    }

    return 0;
}

If, for some reason, the capture interface fails to open the file it will quit the application immediately, instead of going further just to crash at cap.read(frame).

Answer 3

I realised that, the VideoCapture object needs opencv_ffmpeg310_64.dll. Once you copy this dll in your binary folder your VideoCapture object should be able to read video file.