延迟使用OpenCv播放AVI

Question

我通过opencv玩avi，我试图对视频进行一些圆圈检测。只是播放视频很棒但是当我尝试检测圆圈时，视频会变慢。有没有办法让视频播放的速度接近录制的速度？

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

int main(int argc, char** argv)
{
    IplImage*img;
   int key=0;

 CvCapture*capture = cvCaptureFromAVI("C:\\Users\\Nathan\\Desktop\\SnookVid.wmv");

 if(!capture) return 1;

int fps = (int)cvGetCaptureProperty(capture, CV_CAP_PROP_FPS);

cvNamedWindow("circles", 0);


while(key!='q'){
    img = cvQueryFrame( capture );

    if(!img) break;


IplImage* gray = cvCreateImage(cvGetSize(img), IPL_DEPTH_8U, 1);
//IplImage* hsv = cvCreateImage(cvGetSize(img), IPL_DEPTH_8U, 1);
CvMemStorage* storage = cvCreateMemStorage(0);

//covert to grayscale
cvCvtColor(img, gray, CV_BGR2GRAY);

// This is done so as to prevent a lot of false circles from being detected
cvSmooth(gray, gray, CV_GAUSSIAN, 3, 5);

IplImage* canny = cvCreateImage(cvGetSize(img),IPL_DEPTH_8U,1);
//IplImage* rgbcanny = cvCreateImage(cvGetSize(img),IPL_DEPTH_8U,3);
//cvCanny(gray, canny, 50, 70, 3);

//detect circles
CvSeq* circles = cvHoughCircles(gray, storage, CV_HOUGH_GRADIENT, 1, 27, 70, 40,0,0);
//cvCvtColor(canny, rgbcanny, CV_GRAY2BGR);
//cvCvtColor(img,hsv, CV_BGR2HSV);
//draw all detected circles
float* p;
CvScalar s;
int num_red = 22;
for (int i = 0; i < circles->total; i++)
{
     // round the floats to an int
     p = (float*)cvGetSeqElem(circles, i);
     cv::Point center(cvRound(p[0]), cvRound(p[1]));
     int radius = cvRound(p[2]);

     //uchar* ptr;
     //ptr = cvPtr2D(img, center.y, center.x, NULL);
     //printf("B: %d G: %d R: %d\n", ptr[0],ptr[1],ptr[2]);


     s = cvGet2D(img,center.y, center.x);//colour of circle
    printf("B: %f G: %f R: %f\n",s.val[0],s.val[1],s.val[2]);
}

Answer 1

在使用HoughCircles pyrDown或resize #include <opencv2/core/core.hpp> #include <opencv2/highgui/highgui.hpp> #include <opencv2/imgproc/imgproc.hpp> #include <iostream> using namespace std; using namespace cv; int main(int argc, char** argv) { Mat circleBig = imread("circle.png", 0); Mat circleSmall; double scale = 2.0; // INTER_NEAREST is crude, but very fast; you may need INTER_LINEAR here... resize(circleBig, circleSmall, Size(0, 0), 1.0 / scale, 1.0 / scale, cv::INTER_NEAREST); cvtColor(circleBig, circleBig, CV_GRAY2RGB); vector<Vec3f> circles; HoughCircles(circleSmall, circles, CV_HOUGH_GRADIENT, 2, circleSmall.rows >> 2, 200, 100 ); for( size_t i = 0; i < circles.size(); i++ ) { Point center(cvRound(circles[i][0]), cvRound(circles[i][3])); int radius = cvRound(circles[i][4]); // draw the circle center circle( circleBig, scale*center, 3, Scalar(0,255,0), -1, 8, 0 ); // draw the circle outline circle( circleBig, scale*center, scale*radius, Scalar(0,0,255), 3, 8, 0 ); } imshow("circleBig", circleBig); waitKey(); return 0; } 进行处理之前，尝试缩小图像尺寸。

如果要将检测到的圆圈与原始图像一起使用，请将半径和中心乘以您划分图像的系数。减少2倍的比例可以使处理时间减去2-4倍，减去执行比例操作所需的时间。

以下是您可能会如何解决这个问题的简短示例：

HoughCircles

最后，这是我使用的测试图像：

以下是640x480 time: 0.0127101 320x240 time: 0.00408843 检测的时间：

{{1}}

粗略地说，加速3倍！ ：）

Answer 2

你可以尝试mevatron的建议，它肯定会有所作为，这就是我赞成它的原因。

但有一点需要明确的是：视频速度减慢不是源代码中的错误，它也不是OpenCV中的错误。此效果是由CPU不得不花费处理时间对视频的每一帧执行圆检测引起的。你的CPU根本无法快速执行这项任务，无法给你实时的感觉。

问题的标题有点误导，因为你不只是用OpenCV播放AVI。