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常用的USB拍照功能代码: #include#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "uvcTest.h" #define FILE_VIDEO "/dev/video0" #define JPG "./p_w_picpath%d.jpg" BUFTYPE *usr_buf; static unsigned int n_buffer = 0; //set video capture ways(mmap) int init_mmap(int fd) { //to request frame cache, contain requested counts struct v4l2_requestbuffers reqbufs; //request V4L2 driver allocation video cache //this cache is locate in kernel and need mmap mapping memset(&reqbufs, 0, sizeof(reqbufs)); reqbufs.count = 4; reqbufs.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; reqbufs.memory = V4L2_MEMORY_MMAP; if(-1 == ioctl(fd,VIDIOC_REQBUFS,&reqbufs)){ perror("Fail to ioctl 'VIDIOC_REQBUFS'"); exit(EXIT_FAILURE); } n_buffer = reqbufs.count; printf("n_buffer = %d\n", n_buffer); // usr_buf = (BUFTYPE *)calloc(reqbufs.count, sizeof(usr_buf)); usr_buf = new BUFTYPE[reqbufs.count*sizeof(BUFTYPE)]; if(usr_buf == NULL){ printf("Out of memory\n"); exit(-1); } //map kernel cache to user process for(n_buffer = 0; n_buffer < reqbufs.count; ++n_buffer){ //stand for a frame struct v4l2_buffer buf; memset(&buf, 0, sizeof(buf)); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; buf.memory = V4L2_MEMORY_MMAP; buf.index = n_buffer; //check the information of the kernel cache requested if(-1 == ioctl(fd,VIDIOC_QUERYBUF,&buf)) { perror("Fail to ioctl : VIDIOC_QUERYBUF"); exit(EXIT_FAILURE); } usr_buf[n_buffer].length = buf.length; usr_buf[n_buffer].start = (char *)mmap( NULL, buf.length, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, buf.m.offset ); if(MAP_FAILED == usr_buf[n_buffer].start) { perror("Fail to mmap"); exit(EXIT_FAILURE); } } return 0; } //initial camera device int init_camera_device(int fd) { //decive fuction, such as video input struct v4l2_capability cap; //video standard,such as PAL,NTSC struct v4l2_standard std; //frame format struct v4l2_format tv_fmt; //check control struct v4l2_queryctrl query; //detail control value struct v4l2_fmtdesc fmt; int ret; //get the format of video supply memset(&fmt, 0, sizeof(fmt)); fmt.index = 0; //supply to p_w_picpath capture fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; // show all format of supply printf("Support format:\n"); while(ioctl(fd, VIDIOC_ENUM_FMT, &fmt) == 0){ fmt.index++; printf("pixelformat = ''%c%c%c%c''\ndescription = ''%s''\n",fmt.pixelformat & 0xFF, (fmt.pixelformat >> 8) & 0xFF,(fmt.pixelformat >> 16) & 0xFF, (fmt.pixelformat >> 24) & 0xFF,fmt.description); } //check video decive driver capability ret = ioctl(fd, VIDIOC_QUERYCAP, &cap); if(ret < 0){ perror("Fail to ioctl VIDEO_QUERYCAP"); exit(EXIT_FAILURE); } //judge wherher or not to be a video-get device if(!(cap.capabilities & V4L2_BUF_TYPE_VIDEO_CAPTURE)) { printf("The Current device is not a video capture device\n"); exit(-1); } //judge whether or not to supply the form of video stream if(!(cap.capabilities & V4L2_CAP_STREAMING)) { printf("The Current device does not support streaming i/o\n"); exit(EXIT_FAILURE); } //set the form of camera capture data tv_fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; tv_fmt.fmt.pix.width = 100; tv_fmt.fmt.pix.height = 100; tv_fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG; tv_fmt.fmt.pix.field = V4L2_FIELD_INTERLACED; if (ioctl(fd, VIDIOC_S_FMT, &tv_fmt)< 0) { printf("VIDIOC_S_FMT\n"); exit(-1); close(fd); } //initial video capture way(mmap) init_mmap(fd); return 0; } int open_camera_device(const char *dev_name) { int fd; QString devName =QString(QLatin1String(dev_name)); QString strDevName = QString("sudo chmod 777 %1").arg(devName); qDebug()<<"strDevName"< 0) { for(;;) { fd_set fds; struct timeval tv; int r; FD_ZERO(&fds); FD_SET(fd,&fds); /*Timeout*/ tv.tv_sec = 2; tv.tv_usec = 0; r = select(fd + 1,&fds,NULL,NULL,&tv); if(-1 == r) { if(EINTR == errno) continue; perror("Fail to select"); exit(EXIT_FAILURE); } if(0 == r) { fprintf(stderr,"select Timeout\n"); exit(-1); } if(read_frame(fd,workOrder)) break; } } return 0; } void stop_capture(int fd) { enum v4l2_buf_type type; type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if(-1 == ioctl(fd,VIDIOC_STREAMOFF,&type)) { qDebug()<<"stop"<