v4l2帧的tcp传输模板

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <error.h>
#include <string.h>
#include<sys/types.h>
#include<sys/stat.h>
#include <fcntl.h>
#include <linux/videodev2.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <strings.h>
struct buffer
{
  void* start;
  unsigned int length;
}*buffers;
int main(void)
{
  char id[10];
  int ret;
  int sockfd; //套接字描述符
  sockfd = socket(AF_INET ,SOCK_STREAM, 0); //创建通信套接字（TCP）
  if(sockfd == -1)
  {
    printf("socket failed\n");
    exit(-1);
  }
  //定义addr存入本机地址信息
  struct sockaddr_in addr;
    addr.sin_family = AF_INET; //协议
  addr.sin_port = htons(9999);    //端口
  addr.sin_addr.s_addr= inet_addr("127.0.0.1"); //服务器地址
  ret = connect(sockfd, (struct sockaddr *)&addr, sizeof(addr));  //连接tcp客服端
  // printf("sdf\n");
  if(ret == -1)
  {
    printf("connect failed!\n");
    return 0;
    }
      printf("connect success!\n");
  strcpy(id, "video");
  send(sockfd, id, sizeof(id),0);//发送身份信息
    //打开摄像头
  int fd = open("/dev/video0",O_RDWR);
  if(fd<0)
    return -1;
  // 查看设备属性
  struct v4l2_capability cap;
  ioctl(fd,VIDIOC_QUERYCAP,&cap);
  printf("Driver Name:%s\nCard Name:%s\nBus info:%s\nDriver Version:%u.%u.%u\n",cap.driver,cap.card,cap.bus_info,(cap.version>>16)&0XFF, (cap.version>>8)&0XFF,cap.version&0XFF);
  //设置摄像头格式
  struct v4l2_format fmt;
  fmt.fmt.pix.width = 1024;
  fmt.fmt.pix.height = 768;
  fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG;
  ioctl(fd, VIDIOC_S_FMT,&fmt);
  //申请摄像头采集图片的buf
  struct v4l2_requestbuffers req;
  memset(&req,0,sizeof(req));
  req.count = 3; //缓冲个数 
  req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  req.memory = V4L2_MEMORY_MMAP;
  ioctl(fd, VIDIOC_REQBUFS,&req);
  // //映射 系统空间 ---> 用户空间
  buffers = (struct buffer*)calloc(req.count, sizeof (*buffers));
  if (!buffers) {
    fprintf(stderr, "Out of memory/n");
    exit(EXIT_FAILURE);
  }
  for (unsigned int n_buffers = 0; n_buffers < req.count; ++n_buffers)
  {
    struct v4l2_buffer buf;
    memset(&buf,0,sizeof(buf));
    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    buf.memory = V4L2_MEMORY_MMAP;
    buf.index = n_buffers;
    // 查询序号为n_buffers 的缓冲区，得到其起始物理地址和大小
    if (-1 == ioctl(fd, VIDIOC_QUERYBUF, &buf)) exit(-1);
    buffers[n_buffers].length = buf.length;
    // 映射内存
    buffers[n_buffers].start = mmap(NULL,buf.length,PROT_READ | PROT_WRITE ,MAP_SHARED,fd, buf.m.offset);
    if (MAP_FAILED == buffers[n_buffers].start) exit(-1);
  }
  // 把四个缓冲帧放入队列，并启动数据流
  unsigned int i;
  enum v4l2_buf_type type;
  for (i = 0; i < 3; ++i) // 将缓冲帧放入队列
  {
    struct v4l2_buffer buf;
    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    buf.memory = V4L2_MEMORY_MMAP;
    buf.index = i;
    ioctl(fd, VIDIOC_QBUF, &buf);
  }
  type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  ioctl(fd, VIDIOC_STREAMON, &type);
  struct v4l2_buffer buf; 
  // CLEAR (buf);
  buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  buf.memory = V4L2_MEMORY_MMAP;
  while(1) {
    ioctl(fd, VIDIOC_DQBUF, &buf); // 从缓冲区取出一个缓冲帧
    // printf("图片大小: %d\n", buf.bytesused);
    send(sockfd, &(buf.bytesused), 4, 0);  //发送图片长度信息
    send(sockfd, buffers[buf.index].start, buf.bytesused, 0);//发送图片
    ioctl(fd, VIDIOC_QBUF, &buf);   // 从缓冲区放回一个缓冲帧
    // break;
    usleep(500);
  }
  //关闭摄像头
  close(sockfd);
  close(fd);
    return 0;
}