Linux下V4L2拍照



一、源码test.c

1. #include <fcntl.h>
2. #include <stdlib.h>
3. #include <sys/mman.h>
4. #include <linux/videodev2.h>
6. int main(){
7. //////
8. int fd = open("/dev/video0",O_RDWR);
9. printf("TK------->>>fd is %d\n",fd);
10. //////
11. struct v4l2_capability cap;
12. ioctl(fd,VIDIOC_QUERYCAP,&cap);
13. printf("TK---------->>>>>Driver Name:%s\nCard Name:%s\nBus info:%s\n",cap.driver,cap.card,cap.bus_info);
14. //////
15. struct v4l2_fmtdesc fmtdesc;
16. fmtdesc.index = 0; fmtdesc.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
17. while(ioctl(fd,VIDIOC_ENUM_FMT,&fmtdesc) != -1){
18. printf("TK-------->>>>>fmtdesc.description is %s\n",fmtdesc.description);
19. fmtdesc.index ++;
20. }
21. //////
22. struct v4l2_format fmt;
23. fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
24. ioctl(fd,VIDIOC_G_FMT,&fmt);
25. printf("TK----------->>>>>fmt.fmt.width is %d\nfmt.fmt.pix.height is %d\nfmt.fmt.pix.colorspace is %d\n",fmt.fmt.pix.width,fmt.fmt.pix.height,fmt.fmt.pix.colorspace);
26. //////
27. struct v4l2_requestbuffers req;
28. req.count = 4;
29. req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
30. req.memory = V4L2_MEMORY_MMAP;
31. ioctl(fd,VIDIOC_REQBUFS,&req);
32. struct buffer{
33. void *start;
34. unsigned int length;
35. }*buffers;
36. buffers = (struct buffer*)calloc (req.count, sizeof(*buffers));
37. unsigned int n_buffers = 0;
38. for(n_buffers = 0; n_buffers < req.count; ++n_buffers){
39. struct v4l2_buffer buf;
40. memset(&buf,0,sizeof(buf));
41. buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
42. buf.memory = V4L2_MEMORY_MMAP;
43. buf.index = n_buffers;
44. if(ioctl(fd,VIDIOC_QUERYBUF,&buf) == -1){
45. printf("TK---------_>>>>>>error\n");
46. close(fd);
47. exit(-1);
48. }
49. buffers[n_buffers].length = buf.length;
50. buffers[n_buffers].start = mmap(NULL,buf.length,PROT_READ|PROT_WRITE,MAP_SHARED,fd,buf.m.offset);
51. if(MAP_FAILED == buffers[n_buffers].start){
52. printf("TK--------__>>>>>error 2\n");
53. close(fd);
54. exit(-1);
55. }
56. }
57. ////
58. unsigned int i;
59. enum v4l2_buf_type type;
60. for(i = 0; i < 4; i++){
61. struct v4l2_buffer buf;
62. buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
63. buf.memory = V4L2_MEMORY_MMAP;
64. buf.index = i;
65. ioctl(fd,VIDIOC_QBUF,&buf);
66. }
67. type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
68. ioctl(fd,VIDIOC_STREAMON,&type);
69. ////
70. struct v4l2_buffer buf;
71. buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
72. buf.memory = V4L2_MEMORY_MMAP;
73. ioctl(fd,VIDIOC_DQBUF,&buf);
74. char path[20];
75. snprintf(path,sizeof(path),"./yuyv%d",buf.index);
76. int fdyuyv = open(path,O_WRONLY|O_CREAT,00700);
77. printf("TK--------->>>>fdyuyv is %d\n",fdyuyv);
78. int resultyuyv = write(fdyuyv,buffers[buf.index].start,1280*720*2);
79. printf("TK--------->>>resultyuyv is %d\n",resultyuyv);
80. close(fdyuyv);
81. ////
82. close(fd);
83. return 0;
84. }

二、编译运行

gcc test.c -o rest

./test

三、结果

在本目录下生成yuyv0这样一个文件，是jpeg编码后的文件。

四、极力推荐一款window下的图像查看工具YUVviewerPlus

  该工具可以将原始yuyv（如yuv422选择yuy2，需要后缀改为.yuv），rgb（rgb24选择gbmp24，需要后缀改为.bmp）等数据文件显示出来。

  另外说明：yuyv和jpeg数据大小为width*height*2；rgb为width*height*3；单位为Bytes。