避免以后要用到，备用
#include <stdio.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <linux/videodev2.h>
#include<sys/ioctl.h>
#include <setjmp.h>
#include <unistd.h>#define CAM_DEV "/dev/video14"
#define WIDTH 1920 // 图片的宽度
#define HEIGHT 1080 // 图片的高度
#define NB_BUFFER 4 //memory block number
struct pic_data
{unsigned char *tmpbuffer[NB_BUFFER];unsigned int tmpbytesused[NB_BUFFER];
}pic;int cam_fd;/*
Description.:Initalize V4L2 driver.
*/
int v4l2_init(void)
{int i;int ret = 0;// 1、Open camera deviceif((cam_fd = open(CAM_DEV,O_RDWR)) == -1){perror("ERROR opening V4L interface.");return -1;}// 2、Judge if the device is a camera device struct v4l2_capability cam_cap;if(ioctl(cam_fd,VIDIOC_QUERYCAP,&cam_cap) == -1){perror("Error opening device %s: unable to query device.");return -1;}if((cam_cap.capabilities & V4L2_CAP_VIDEO_CAPTURE) == 0) {perror("ERROR video capture not supported.");return -1;}// 3、Setting output parameter.struct v4l2_format v4l2_fmt;v4l2_fmt.type = V4L2_CAP_VIDEO_CAPTURE;v4l2_fmt.fmt.pix.width = WIDTH;v4l2_fmt.fmt.pix.height = HEIGHT;v4l2_fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG;if (ioctl (cam_fd, VIDIOC_S_FMT, &v4l2_fmt) == -1) { perror("ERROR camera VIDIOC_S_FMT Failed.");return -1;}// 4、Check whether the parameters are set successfully if (ioctl (cam_fd, VIDIOC_G_FMT, &v4l2_fmt) == -1) {perror("ERROR camera VIDIOC_G_FMT Failed.");return -1;}if (v4l2_fmt.fmt.pix.pixelformat == V4L2_PIX_FMT_MJPEG){printf("Set VIDIOC_S_FMT sucessful\n");}// 5、Require buffer to store image datastruct v4l2_requestbuffers v4l2_req;v4l2_req.count = NB_BUFFER;v4l2_req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;v4l2_req.memory = V4L2_MEMORY_MMAP;if (ioctl (cam_fd, VIDIOC_REQBUFS, &v4l2_req) == -1) {perror("ERROR camera VIDIOC_REQBUFS Failed.");return -1;} // 6、Start memory mapstruct v4l2_buffer v4l2_buf;v4l2_buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;v4l2_buf.memory = V4L2_MEMORY_MMAP;for(i = 0; i < NB_BUFFER; i++) {v4l2_buf.index = i;if(ioctl(cam_fd, VIDIOC_QUERYBUF, &v4l2_buf) < 0){perror("Unable to query buffer.");return -1;}pic.tmpbuffer[i] = (unsigned char*)mmap(NULL, v4l2_buf.length, PROT_READ, MAP_SHARED, cam_fd, v4l2_buf.m.offset);if(pic.tmpbuffer[i] == MAP_FAILED){perror("Unable to map buffer.");return -1;}if(ioctl(cam_fd, VIDIOC_QBUF, &v4l2_buf) < 0){perror("Unable to queue buffer.");return -1;}}//7、Open stream input int type = V4L2_BUF_TYPE_VIDEO_CAPTURE;if(ioctl(cam_fd, VIDIOC_STREAMON, &type) < 0){perror("Unable to start capture.");return -1;}return 0;
}/*
Description.:Get a jpeg image and save.
*/
int v4l2Grab(void)
{//8、Get a image struct v4l2_buffer buff;buff.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buff.memory = V4L2_MEMORY_MMAP;if(ioctl(cam_fd, VIDIOC_DQBUF, &buff) < 0){printf("camera VIDIOC_DQBUF Failed.\n");usleep(1000*1000);return -1;}pic.tmpbytesused[buff.index] = buff.bytesused;printf("size : %d\n",pic.tmpbytesused[buff.index]); //9、Save image./*int jpg_fd = open("1.jpeg",O_RDWR|O_CREAT,00700);if(jpg_fd == -1){printf("open ipg Failed!\n ");return -1; }int writesize = write(jpg_fd, pic.tmpbuffer[buff.index], pic.tmpbytesused[buff.index]);printf("Write successfully size : %d\n",writesize);close(jpg_fd);*///10、Queue the buffers.if(ioctl(cam_fd, VIDIOC_QBUF, &buff) < 0){printf("camera VIDIOC_QBUF Failed.");usleep(1000*1000);return -1;}return 0;
}/*
Description.:Release resource
*/
int v4l2_close(void)
{// Remove mmap.int i;for(i=0; i<NB_BUFFER; i++)munmap(pic[0].tmpbuffer[i],pic[0].tmpbytesused[i]);close(cam_fd);return 0;
}/*
Description.:main
*/
int main(int argc, char* argv[])
{v4l2_init();while(1){ v4l2Grab();}v4l2_close(); return 0;
}
