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 <stdio.h>
- #include <stdlib.h>
- #include <string.h>
- #include <assert.h>
- #include <getopt.h> /* getopt_long() */
- #include <fcntl.h> /* low-level i/o */
- #include <unistd.h>
- #include <errno.h>
- #include <sys/stat.h>
- #include <sys/types.h>
- #include <sys/time.h>
- #include <sys/mman.h>
- #include <sys/ioctl.h>
-
- #include <linux/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
【作者】
张昺华
【新浪微博】 张昺华--sky
【twitter】 @sky2030_
【facebook】 张昺华 zhangbinghua
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