OpenCV视频播放

时间:2022-05-23 求则得之，舍则失之人气:0

介绍

本文将介绍基于OpenCV实现视频的循环播放。

有以下三个步骤：

首先设置一个frame的设置参数frame_counter，值为0
在读帧时间，将每次加一
当 frame_counter 达到视频总帧数时，将当前的帧设置为 0

视频总帧数：CAP_PROP_FRAME_COUNT

设置当前的帧：CAP_PROP_POS_FRAMES

VideoCaptureProperties通用属性标识符参考地址。

1.Python+OpenCV实现

import cv2

cap = cv2.VideoCapture("001.mp4")
frame_counter = 0

while (cap.isOpened()):
   ret, frame = cap.read()

   frame_counter += 1
   if frame_counter == int(cap.get(cv2.CAP_PROP_FRAME_COUNT)):
      frame_counter = 0
      cap.set(cv2.CAP_PROP_POS_FRAMES, 0)

   cv2.imshow("frame", frame)
   key = cv2.waitKey(1)
   # ESC
   if key == 27:
      break
cap.release()
cv2.destroyAllWindows()

2.C++ + OpenCV实现

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>

int main() {
 
    cv::Mat frame;
    cv::VideoCapture cap("001.mp4");   
      
    int frame_counter = 0;
    while (true)
    {
      cap >> frame;
      if (!frame.data)
      {
         printf("Image not loaded");
         return -1;
      }
      
      frame_counter += 1;
      if (frame_counter == int(cap.get(cv::CAP_PROP_FRAME_COUNT))){
          frame_counter = 0;
          cap.set(cv::CAP_PROP_POS_FRAMES, 0);
      }

      cv::imshow("demo", frame);
      char(key)=(char)cv::waitKey(1);
      if(key==27)
          break;
     }

 
    return 0;
}

补充

当然，OpenCV不仅能实现视频的循环播放，还能实现视频的倒放

下面将用C语言实现视频的倒放，以下是示例代码

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

int main(int argc, char* argv[]) {undefined
    int i = 0, j = 0, k = 0;
    cvNamedWindow("Example3", CV_WINDOW_AUTOSIZE);
    CvCapture* capture = 0;
    capture = cvCreateFileCapture("gr18.avi");
    
    if (!capture) {undefined
    return -1;
    }
    
    
    IplImage *out = cvQueryFrame(capture);//Init the video read

                                          //用于确定帧数
    while ((out = cvQueryFrame(capture)) != NULL) {undefined
        k++;
    }
    cvReleaseCapture(&capture);
    capture = cvCreateFileCapture("gr18.avi");
    out = cvQueryFrame(capture);//没有它J会多一帧。

    
    double fps = cvGetCaptureProperty(
        capture,
        CV_CAP_PROP_FPS
        );
    
    CvSize size = cvSize(
        (int)cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_WIDTH),
        (int)cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_HEIGHT)
        );
    
    CvVideoWriter *writer = cvCreateVideoWriter(
        "gr13.avi",
        CV_FOURCC('M', 'J', 'P', 'G'),
        fps,
        size
        , 1
        );
    IplImage* logpolar_frame = cvCreateImage(
        size,
        IPL_DEPTH_8U,
        3
        );
    //out = cvCloneImage(img);

    int booll = 1;
    while ((out = cvQueryFrame(capture)) != NULL)
    {undefined
        
        i = 0;
    
        j++;;

        booll = 0;
        if (j == k)//用于从第J帧开始写入
        {undefined
            cvShowImage("Example3", out);
            cvWaitKey(1);

            cvWriteFrame(writer, out);
            k--; j = 0;

            //重复初始化
            capture = cvCreateFileCapture("gr18.avi");
            out = cvQueryFrame(capture);
        }
        //j++;


        if (k == 0)break;
    }
    printf("||%d %d", k, j); getchar();
    cvReleaseVideoWriter(&writer);
    cvReleaseImage(&logpolar_frame);
    cvReleaseCapture(&capture);
    //cvReleaseCapture(&capture);
    cvDestroyWindow("Example3");
    

    return(0);
}

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