linux下網路攝影機映像資料的擷取

來源:互聯網
上載者:User

2.6.32核心,V4L2架構

親自測試可用

在友善之臂MINI2440開發板上測試可用

來源程式如下

 

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <assert.h>#include <getopt.h>            #include <fcntl.h>             #include <unistd.h>#include <errno.h>#include <malloc.h>#include <sys/stat.h>#include <sys/types.h>#include <sys/time.h>#include <sys/mman.h>#include <sys/ioctl.h>#include <asm/types.h>         #include <linux/videodev2.h>#define CLEAR(x) memset (&(x), 0, sizeof (x))struct buffer {        void *                  start;        size_t                  length;};static char *           dev_name        = "/dev/video0";//網路攝影機裝置名稱static int              fd              = -1;struct buffer *         buffers         = NULL;static unsigned int     n_buffers       = 0;FILE *file_fd;static unsigned long file_length;static unsigned char *file_name;////////////////////////////////////////////////////////擷取一幀資料//////////////////////////////////////////////////////static int read_frame (void){struct v4l2_buffer buf;unsigned int i;CLEAR (buf);buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf.memory = V4L2_MEMORY_MMAP;int ff = ioctl (fd, VIDIOC_DQBUF, &buf);if(ff<0)printf("failture\n"); //出列採集的幀緩衝assert (buf.index < n_buffers);printf ("buf.index dq is %d,\n",buf.index);fwrite(buffers[buf.index].start, buffers[buf.index].length, 1, file_fd); //將其寫入檔案中  ff=ioctl (fd, VIDIOC_QBUF, &buf); //再將其入列if(ff<0)printf("failture VIDIOC_QBUF\n"); return 1;}int main (int argc,char ** argv){struct v4l2_capability cap; struct v4l2_format fmt;unsigned int i;enum v4l2_buf_type type;file_fd = fopen("test.jpg", "wb");                 //圖片檔案名稱fd = open (dev_name, O_RDWR /* required */ |O_NONBLOCK);//開啟裝置if(fd<0){perror("open faiure!");exit(1);}int ff=ioctl (fd, VIDIOC_QUERYCAP, &cap);               //擷取網路攝影機參數if(ff<0)printf("failture VIDIOC_QUERYCAP\n");struct v4l2_fmtdesc fmt1;    int ret;memset(&fmt1, 0, sizeof(fmt1));fmt1.index = 0;            //初始化為0fmt1.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;while ((ret = ioctl(fd, VIDIOC_ENUM_FMT, &fmt1)) == 0) {fmt1.index++;printf("{ pixelformat = '%c%c%c%c', description = '%s' }\n",fmt1.pixelformat & 0xFF, (fmt1.pixelformat >> 8) & 0xFF,(fmt1.pixelformat >> 16) & 0xFF, (fmt1.pixelformat >> 24) & 0xFF,fmt1.description);}CLEAR (fmt);fmt.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;//fmt.fmt.pix.width       = 640; //fmt.fmt.pix.height      = 480;fmt.fmt.pix.width       = 320; fmt.fmt.pix.height      = 240;fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_JPEG;//V4L2_PIX_FMT_YUYV;//V4L2_PIX_FMT_YVU420;//V4L2_PIX_FMT_YUYV;fmt.fmt.pix.field       = V4L2_FIELD_INTERLACED;ff = ioctl (fd, VIDIOC_S_FMT, &fmt); //設定映像格式if(ff<0)printf("failture VIDIOC_S_FMT\n");file_length = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height; //計算圖片大小struct v4l2_requestbuffers req;CLEAR (req);req.count               = 1;req.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;req.memory              = V4L2_MEMORY_MMAP;ff=ioctl (fd, VIDIOC_REQBUFS, &req); //申請緩衝,count是申請的數量if(ff<0)printf("failture VIDIOC_REQBUFS\n");if (req.count < 1)printf("Insufficient buffer memory\n");buffers = calloc (req.count, sizeof (*buffers));//記憶體中建立對應空間for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {struct v4l2_buffer buf;   //驅動中的一幀CLEAR (buf);buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf.memory      = V4L2_MEMORY_MMAP;buf.index       = n_buffers;if (-1 == ioctl (fd, VIDIOC_QUERYBUF, &buf)) //映射使用者空間printf ("VIDIOC_QUERYBUF error\n");buffers[n_buffers].length = buf.length;buffers[n_buffers].start =mmap (NULL /* start anywhere */,    //通過mmap建立映射關係buf.length,PROT_READ | PROT_WRITE /* required */,MAP_SHARED /* recommended */,fd, buf.m.offset);if (MAP_FAILED == buffers[n_buffers].start)printf ("mmap failed\n");    }for (i = 0; i < n_buffers; ++i) {struct v4l2_buffer buf;CLEAR (buf);buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf.memory      = V4L2_MEMORY_MMAP;buf.index       = i;if (-1 == ioctl (fd, VIDIOC_QBUF, &buf))//申請到的緩衝進入列隊printf ("VIDIOC_QBUF failed\n");}                type = V4L2_BUF_TYPE_VIDEO_CAPTURE;if (-1 == ioctl (fd, VIDIOC_STREAMON, &type)) //開始捕捉映像資料printf ("VIDIOC_STREAMON failed\n");for (;;) //這一段涉及到非同步IO{fd_set fds;struct timeval tv;int r;FD_ZERO (&fds);//將指定的檔案描述符集清空FD_SET (fd, &fds);//在檔案描述符集合中增加一個新的檔案描述符   /* Timeout. */tv.tv_sec = 2;tv.tv_usec = 0;r = select (fd + 1, &fds, NULL, NULL, &tv);//判斷是否可讀(即網路攝影機是否準備好),tv是定時if (-1 == r) {if (EINTR == errno)continue;printf ("select err\n");}if (0 == r) {fprintf (stderr, "select timeout\n");exit (EXIT_FAILURE);}if (read_frame ())//如果可讀,執行read_frame ()函數,並跳出迴圈break;}unmap:for (i = 0; i < n_buffers; ++i)if (-1 == munmap (buffers[i].start, buffers[i].length))printf ("munmap error");type = V4L2_BUF_TYPE_VIDEO_CAPTURE;       if (-1 == ioctl(fd, VIDIOC_STREAMOFF, &type))           printf("VIDIOC_STREAMOFF"); close (fd);fclose (file_fd);return 0;}

 

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