Getting the correct frame rate

edit

could you try your video with the code below

#include <opencv2/highgui.hpp>
#include <opencv2/imgproc.hpp>
#include <ctime>
#include <windows.h>

using namespace cv;

int main(int argc, char** argv)
{
    char* filename = argc >= 2 ? argv[1] : (char*)"c:/768x576.avi";

    VideoCapture capture(filename); // open video file
    if (!capture.isOpened())  // check if we succeeded
        return -1;

    int fps_of_video = (int)capture.get(CAP_PROP_FPS);
    int time_to_wait = 1000 / fps_of_video;

    int frameCounter = 0;
    int tick = 0;
    int fps = fps_of_video;
    std::time_t timeBegin = std::time(0);

    for (;;)
    {
        double time_start = (double)getTickCount();

        Mat frame;
        capture >> frame; // get a new frame

        if (frame.empty())
        {
            break;
        }

        frameCounter++;

        std::time_t timeNow = std::time(0) - timeBegin;

        if (timeNow - tick >= 1)
        {
            tick++;
            fps = frameCounter;
            frameCounter = 0;
        }

        cv::putText(frame, cv::format("Original FPS of Video=%d", fps_of_video), cv::Point(30, 50), cv::FONT_HERSHEY_SIMPLEX, 0.8, cv::Scalar(0, 0, 255));
        cv::putText(frame, cv::format("Average FPS=%d", fps), cv::Point(30, 80), cv::FONT_HERSHEY_SIMPLEX, 0.8, cv::Scalar(0, 0, 255));

        imshow("Video Player", frame);

        if (waitKey(1) == 27) break;

        // wait for some time to correct FPS
        while (time_to_wait > ((double)getTickCount() - time_start) / getTickFrequency() * 1000)
        {
            //http://stackoverflow.com/questions/1157209/is-there-an-alternative-sleep-function-in-c-to-milliseconds
            Sleep(1);
        }
    }
    return 0;
}