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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1. /*
2. * V4L2 video capture example
3. * AUTHOT : WANGTISHENG
4. * DATA : 2013-12-18
5. */
6. #include <stdio.h>
7. #include <stdlib.h>
8. #include <string.h>
9. #include <assert.h>
10. #include <getopt.h> /* getopt_long() */
11. #include <fcntl.h> /* low-level i/o */
12. #include <unistd.h>
13. #include <errno.h>
14. #include <sys/stat.h>
15. #include <sys/types.h>
16. #include <sys/time.h>
17. #include <sys/mman.h>
18. #include <sys/ioctl.h>
19. #include <linux/videodev2.h>
20. #define CLEAR(x) memset(&(x), 0, sizeof(x))
21. struct buffer {
22. void *start;
23. size_t length;
24. };
25. static char *dev_name;
26. static int fd = -1;        //DEVICE NUMBER
27. struct buffer *buffers;
28. static unsigned int n_buffers;
29. static int frame_count = 70;
30. FILE *fp;                                //FILE POINTOR
31. static void errno_exit(const char *s)
32. {
33. fprintf(stderr, "%s error %d, %s\n", s, errno, strerror(errno));
34. exit(EXIT_FAILURE);
35. }
36. static int xioctl(int fh, int request, void *arg)
37. {
38. int r;
39. do {
40. r = ioctl(fh, request, arg);
41. } while (-1 == r && EINTR == errno);
42. return r;
43. }
44. //处理函数
45. static void process_image(const void *p, int size)
46. {
47. fwrite(p,size, 1, fp);
48. }
49. static int read_frame(FILE *fp)
50. {
51. struct v4l2_buffer buf;
52. CLEAR(buf);
53. buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
54. buf.memory = V4L2_MEMORY_MMAP;
55. if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf))
56. errno_exit("VIDIOC_DQBUF");
57. process_image(buffers[buf.index].start, buf.bytesused);
58. if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
59. errno_exit("VIDIOC_QBUF");
60. return 1;
61. }
62. static void mainloop(void)
63. {
64. unsigned int count;
65. count = frame_count;
66. while (count-- > 0) {
67. printf("No.%d\n",frame_count - count);        //显示当前帧数目
68. read_frame(fp);
69. }
70. printf("\nREAD AND SAVE DONE!\n");
71. }
72. static void stop_capturing(void)
73. {
74. enum v4l2_buf_type type;
75. type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
76. if (-1 == xioctl(fd, VIDIOC_STREAMOFF, &type))
77. errno_exit("VIDIOC_STREAMOFF");
78. }
79. static void start_capturing(void)
80. {
81. unsigned int i;
82. enum v4l2_buf_type type;
83. for (i = 0; i < n_buffers; ++i) {
84. struct v4l2_buffer buf;
85. CLEAR(buf);
86. buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
87. buf.memory = V4L2_MEMORY_MMAP;
88. buf.index = i;
89. if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
90. errno_exit("VIDIOC_QBUF");
91. }
92. type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
93. if (-1 == xioctl(fd, VIDIOC_STREAMON, &type))
94. errno_exit("VIDIOC_STREAMON");
95. }
96. static void uninit_device(void)
97. {
98. unsigned int i;
99. for (i = 0; i < n_buffers; ++i)
100. if (-1 == munmap(buffers[i].start, buffers[i].length))
101. errno_exit("munmap");
102. free(buffers);
103. }
104. static void init_mmap(void)
105. {
106. struct v4l2_requestbuffers req;
107. CLEAR(req);
108. req.count = 4;
109. req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
110. req.memory = V4L2_MEMORY_MMAP;
111. if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) {
112. if (EINVAL == errno) {
113. fprintf(stderr, "%s does not support "
114. "memory mapping\n", dev_name);
115. exit(EXIT_FAILURE);
116. } else {
117. errno_exit("VIDIOC_REQBUFS");
118. }
119. }
120. if (req.count < 2) {
121. fprintf(stderr, "Insufficient buffer memory on %s\n",
122. dev_name);
123. exit(EXIT_FAILURE);
124. }
125. buffers = calloc(req.count, sizeof(*buffers));
126. if (!buffers) {
127. fprintf(stderr, "Out of memory\n");
128. exit(EXIT_FAILURE);
129. }
130. for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {
131. struct v4l2_buffer buf;
132. CLEAR(buf);
133. buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
134. buf.memory = V4L2_MEMORY_MMAP;
135. buf.index = n_buffers;
136. if (-1 == xioctl(fd, VIDIOC_QUERYBUF, &buf))
137. errno_exit("VIDIOC_QUERYBUF");
138. buffers[n_buffers].length = buf.length;
139. buffers[n_buffers].start =
140. mmap(NULL /* start anywhere */,
141. buf.length,
142. PROT_READ | PROT_WRITE /* required */,
143. MAP_SHARED /* recommended */,
144. fd, buf.m.offset);
145. if (MAP_FAILED == buffers[n_buffers].start)
146. errno_exit("mmap");
147. }
148. }
149. static void init_device(void)
150. {
151. struct v4l2_capability cap;
152. struct v4l2_format fmt;
153. if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &cap)) {        //测试参数
154. if (EINVAL == errno) {
155. fprintf(stderr, "%s is no V4L2 device\n",
156. dev_name);
157. exit(EXIT_FAILURE);
158. } else {
159. errno_exit("VIDIOC_QUERYCAP");
160. }
161. }
162. if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
163. fprintf(stderr, "%s is no video capture device\n",
164. dev_name);
165. exit(EXIT_FAILURE);
166. }
167. if (!(cap.capabilities & V4L2_CAP_STREAMING)) {
168. fprintf(stderr, "%s does not support streaming i/o\n",
169. dev_name);
170. exit(EXIT_FAILURE);
171. }
172. CLEAR(fmt);
173. fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
174. fmt.fmt.pix.width = 640;
175. fmt.fmt.pix.height = 480;
176. fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
177. fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
178. if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))        //设置格式
179. errno_exit("VIDIOC_S_FMT");
180. init_mmap();
181. }
182. static void close_device(void)
183. {
184. if (-1 == close(fd))
185. errno_exit("close");
186. fd = -1;
187. }
188. static void open_device(void)
189. {
190. //加上O_NONBLOCK会出现如下错误
191. //VIDIOC_DQBUF error 11, Resource temporarily unavailable
192. fd = open(dev_name, O_RDWR /* required */ /*| O_NONBLOCK*/, 0);
193. if (-1 == fd) {
194. fprintf(stderr, "Cannot open '%s': %d, %s\n",
195. dev_name, errno, strerror(errno));
196. exit(EXIT_FAILURE);
197. }
198. }
199. int main(int argc, char **argv)
200. {
201. dev_name = "/dev/video0";
202. if(argc != 2)
203. {
204. printf("usage :%s filename\n", argv[0]);
205. exit(0);
206. }
207. if ((fp = fopen(argv[1], "w")) == NULL) {
208. perror("Creat file failed");
209. exit(0);
210. }
211. open_device();
212. init_device();
213. start_capturing();
214. mainloop();                //主要处理均在该函数中实现
215. fclose(fp);
216. stop_capturing();
217. uninit_device();
218. close_device();
219. //fprintf(stderr, "\n");
220. return 0;
221. }

Makefile   

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1. v4l2_capture_example:v4l2_capture_example.c
2. gcc -Wall -o $@ $<
3. clean:
4. 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