Ubuntu10.04中利用V4L2读取摄像头数据并保存成文件【转】

转自：http://blog.chinaunix.net/uid-29339876-id-4042245.html

利用V4L2读取UVC摄像头数据并保存成视频文件，主要参考http://linuxtv.org/downloads/v4l-dvb-apis/index.html中的示例Appendix D. Video Capture Example，将读取的文件保存在当前目录下的file.yuv中，修改后的完成代码如下：
    

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 /*
  * V4L2 video capture example
  * AUTHOT : WANGTISHENG
  * DATA : 2013-12-18
  */
 #include .h>
 #include .h>
 #include <string.h>
 #include .h>
 #include .h> /* getopt_long() */
 #include .h> /* low-level i/o */
 #include .h>
 #include .h>
 #include /stat.h>
 #include /types.h>
 #include /time.h>
 #include /mman.h>
 #include /ioctl.h>

 #include /videodev2.h>

 #define CLEAR(x) memset(&(x), 0, sizeof(x))

 struct buffer {
         void *start;
         size_t length;
 };

 static char *dev_name;
 static int fd = -1;        //DEVICE NUMBER
 struct buffer *buffers;
 static unsigned int n_buffers;
 static int frame_count = 70;
 FILE *fp;                                //FILE POINTOR

 static void errno_exit(const char *s)
 {
         fprintf(stderr, "%s error %d, %s\n", s, errno, strerror(errno));
         exit(EXIT_FAILURE);
 }

 static int xioctl(int fh, int request, void *arg)
 {
         int r;
         do {
                 r = ioctl(fh, request, arg);
         } while (-1 == r && EINTR == errno);
         return r;
 }
 //处理函数
 static void process_image(const void *p, int size)
 {
         fwrite(p,size, 1, fp);
 }

 static int read_frame(FILE *fp)
 {
         struct v4l2_buffer buf;
         CLEAR(buf);

         buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
         buf.memory = V4L2_MEMORY_MMAP;

         if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf))
                 errno_exit("VIDIOC_DQBUF");

         process_image(buffers[buf.index].start, buf.bytesused);

         if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
             errno_exit("VIDIOC_QBUF");

         return 1;
 }

 static void mainloop(void)
 {
         unsigned int count;
         count = frame_count;
         while (count-- > 0) {
             printf("No.%d\n",frame_count - count);        //显示当前帧数目
             read_frame(fp);
         }
         printf("\nREAD AND SAVE DONE!\n");
 }

 static void stop_capturing(void)
 {
         enum v4l2_buf_type type;

         type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
         if (-1 == xioctl(fd, VIDIOC_STREAMOFF, &type))
             errno_exit("VIDIOC_STREAMOFF");
 }

 static void start_capturing(void)
 {
         unsigned int i;
         enum v4l2_buf_type type;

         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 == xioctl(fd, VIDIOC_QBUF, &buf))
                         errno_exit("VIDIOC_QBUF");
         }
         type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
         if (-1 == xioctl(fd, VIDIOC_STREAMON, &type))
                 errno_exit("VIDIOC_STREAMON");
 }

 static void uninit_device(void)
 {
         unsigned int i;

         for (i = 0; i < n_buffers; ++i)
                 if (-1 == munmap(buffers[i].start, buffers[i].length))
                         errno_exit("munmap");

         free(buffers);
 }



 static void init_mmap(void)
 {
         struct v4l2_requestbuffers req;

         CLEAR(req);

         req.count = 4;
         req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
         req.memory = V4L2_MEMORY_MMAP;

         if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) {
                 if (EINVAL == errno) {
                         fprintf(stderr, "%s does not support "
                                  "memory mapping\n", dev_name);
                         exit(EXIT_FAILURE);
                 } else {
                         errno_exit("VIDIOC_REQBUFS");
                 }
         }

         if (req.count < 2) {
                 fprintf(stderr, "Insufficient buffer memory on %s\n",
                          dev_name);
                 exit(EXIT_FAILURE);
         }

         buffers = calloc(req.count, sizeof(*buffers));

         if (!buffers) {
                 fprintf(stderr, "Out of memory\n");
                 exit(EXIT_FAILURE);
         }

         for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {
                 struct v4l2_buffer buf;

                 CLEAR(buf);

                 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
                 buf.memory = V4L2_MEMORY_MMAP;
                 buf.index = n_buffers;

                 if (-1 == xioctl(fd, VIDIOC_QUERYBUF, &buf))
                         errno_exit("VIDIOC_QUERYBUF");

                 buffers[n_buffers].length = buf.length;
                 buffers[n_buffers].start =
                         mmap(NULL /* start anywhere */,
                               buf.length,
                               PROT_READ | PROT_WRITE /* required */,
                               MAP_SHARED /* recommended */,
                               fd, buf.m.offset);

                 if (MAP_FAILED == buffers[n_buffers].start)
                         errno_exit("mmap");
         }
 }


 static void init_device(void)
 {
         struct v4l2_capability cap;
         struct v4l2_format fmt;

         if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &cap)) {        //测试参数
                 if (EINVAL == errno) {
                         fprintf(stderr, "%s is no V4L2 device\n",
                                  dev_name);
                         exit(EXIT_FAILURE);
                 } else {
                         errno_exit("VIDIOC_QUERYCAP");
                 }
         }

         if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
                 fprintf(stderr, "%s is no video capture device\n",
                          dev_name);
                 exit(EXIT_FAILURE);
         }

         if (!(cap.capabilities & V4L2_CAP_STREAMING)) {
                 fprintf(stderr, "%s does not support streaming i/o\n",
                     dev_name);
                 exit(EXIT_FAILURE);
         }




         CLEAR(fmt);
         fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
         fmt.fmt.pix.width = 640;
         fmt.fmt.pix.height = 480;
         fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
         fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;

         if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))        //设置格式
                 errno_exit("VIDIOC_S_FMT");
         init_mmap();
 }

 static void close_device(void)
 {
         if (-1 == close(fd))
                 errno_exit("close");

         fd = -1;
 }

 static void open_device(void)
 {
         //加上O_NONBLOCK会出现如下错误
         //VIDIOC_DQBUF error 11, Resource temporarily unavailable
         fd = open(dev_name, O_RDWR /* required */ /*| O_NONBLOCK*/, 0);

         if (-1 == fd) {
                 fprintf(stderr, "Cannot open '%s': %d, %s\n",
                          dev_name, errno, strerror(errno));
                 exit(EXIT_FAILURE);
         }
 }


 int main(int argc, char **argv)
 {
         dev_name = "/dev/video0";

         if(argc != 2)
         {
             printf("usage :%s filename\n", argv[0]);
             exit(0);
         }
         if ((fp = fopen(argv[1], "w")) == NULL) {
             perror("Creat file failed");
             exit(0);
         }
         open_device();
         init_device();
         start_capturing();
         mainloop();                //主要处理均在该函数中实现
         fclose(fp);
         stop_capturing();
         uninit_device();
         close_device();
         //fprintf(stderr, "\n");
         return 0;
 }

Makefile   

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 v4l2_capture_example:v4l2_capture_example.c
     gcc -Wall -o $@ $<

 clean:
     rm -rf v4l2_capture_example

make测试
    运行方法
        $ ./v4l2_capture_example file.yuv
    可完成摄像头数据的读取和保存。附上查看YUV格式的软件一枚~~~~~~~
YUV_Tools.rar

转载于:https://www.cnblogs.com/sky-heaven/p/7115061.html