跳帧及使用线程将获取下一帧与处理当前帧同时进行

来源：互联网发布：视频加速软件编辑：程序博客网时间：2024/05/16 07:49

一、前言

对视频进行处理时，为了达到实时处理的效果，可以不必处理每一帧，以下为间隔几帧处理视频，并使用Linux的pthread多线程机制将获取下一帧与处理当前帧异步进行的一个例子

二、代码

//main.c  #include <opencv2/highgui/highgui_c.h>  #include <opencv2/core/core_c.h>  #include <opencv2/imgproc/imgproc_c.h>  #include <stdio.h>  #include <pthread.h>     static IplImage *in;  static IplImage *det;  static IplImage *disp;  static CvCapture *cap;      IplImage* get_frame_from_video(CvCapture *cap , int frame_skip);  void *fetch_in_thread(void *ptr);  void *process_in_thread(void *ptr);    int main()  {      cap = cvCaptureFromFile("../../video2.mp4");      if(!cap) error("Couldn't connect to video.\n");      pthread_t fetch_thread;      pthread_t process_thread;            fetch_in_thread(0);      det = in;      cvNamedWindow("Demo" , 1);            while(1){          if(pthread_create(&fetch_thread, 0, fetch_in_thread, 0)) error("Thread creation failed");  //创建线程获取下一帧图像          if(pthread_create(&process_thread, 0, process_in_thread, 0)) error("Thread creation failed");  //创建线程处理当前帧                        pthread_join(fetch_thread, 0);          pthread_join(process_thread, 0);                cvWaitKey(1);             cvShowImage("Demo" , disp );          cvReleaseImage(&disp);          det = in;                    }                        cvreleasecapture(&cap);      return 0;  }    IplImage* get_frame_from_video(CvCapture *cap, int frame_skip) //间隔frame_hop-1 帧从视频结构读取视频帧  {          IplImage* _src;          static unsigned int counter = 0;          while (counter++ %(frame_skip+1) != 1){               _src = cvQueryFrame(cap);               if (!_src){               return NULL;             }          }          _src = cvQueryFrame(cap);          if (!_src){               return NULL;          }            IplImage *out = cvCloneImage(_src);          return out;    }    void *fetch_in_thread(void *ptr)  //获取帧  {      in = get_frame_from_video(cap , 2);   //      if(in == NULL){          error("no frame readed!");      }  }    void *process_in_thread(void *ptr)  //处理帧  {      IplImage *dst_gray = cvCreateImage(cvGetSize(det),det->depth,1);      cvCvtColor(det,dst_gray,CV_BGR2GRAY); //得到灰度图      cvReleaseImage(&det);      disp = dst_gray;}

三、运行
在当前目录下使用gcc -o main main.c `pkg-config --cflags --libs opencv` -lpthread 编译链接生成可执行文件

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