Linux下摄像头图像数据的获取

Linux 2.6.32内核，V4L2架构

亲自测试可用

在友善之臂MINI2440开发板上测试可用

源程序如下

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

#include <getopt.h>           

#include <fcntl.h>           
#include <unistd.h>
#include <errno.h>
#include <malloc.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <sys/ioctl.h>

#include <asm/types.h>       
#include <linux/videodev2.h>

#define CLEAR(x) memset (&(x), 0, sizeof (x))

struct buffer {
        void *                  start;
        size_t                  length;
};

static char *          dev_name        = "/dev/video0";//摄像头设备名
static int              fd              = -1;
struct buffer *        buffers        = NULL;
static unsigned int    n_buffers      = 0;

FILE *file_fd;
static unsigned long file_length;
static unsigned char *file_name;
//////////////////////////////////////////////////////
//获取一帧数据
//////////////////////////////////////////////////////
static int read_frame (void)
{
 struct v4l2_buffer buf;
 unsigned int i;

CLEAR (buf);
 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
 buf.memory = V4L2_MEMORY_MMAP;
 int ff = ioctl (fd, VIDIOC_DQBUF, &buf);
 if(ff<0)
  printf("failture\n"); //出列采集的帧缓冲

assert (buf.index < n_buffers);
  printf ("buf.index dq is %d,\n",buf.index);
 fwrite(buffers[buf.index].start, buffers[buf.index].length, 1, file_fd); //将其写入文件中
 
 ff=ioctl (fd, VIDIOC_QBUF, &buf); //再将其入列
 if(ff<0)
  printf("failture VIDIOC_QBUF\n");
 return 1;
}

int main (int argc,char ** argv)
{
 struct v4l2_capability cap;
 struct v4l2_format fmt;
 unsigned int i;
 enum v4l2_buf_type type;

file_fd = fopen("test.jpg", "wb");                //图片文件名

fd = open (dev_name, O_RDWR /* required */ |O_NONBLOCK);//打开设备
 if(fd<0)
 { 
  perror("open faiure!");
  exit(1);
 }
 int ff=ioctl (fd, VIDIOC_QUERYCAP, &cap);              //获取摄像头参数
 if(ff<0)
  printf("failture VIDIOC_QUERYCAP\n");

struct v4l2_fmtdesc fmt1;
    int ret;
 memset(&fmt1, 0, sizeof(fmt1));
 fmt1.index = 0;            //初始化为0
 fmt1.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
 while ((ret = ioctl(fd, VIDIOC_ENUM_FMT, &fmt1)) == 0)
 {
  fmt1.index++;
  printf("{ pixelformat = '%c%c%c%c', description = '%s' }\n",fmt1.pixelformat & 0xFF,
    (fmt1.pixelformat >> 8) & 0xFF,(fmt1.pixelformat >> 16) & 0xFF,
    (fmt1.pixelformat >> 24) & 0xFF,fmt1.description);
 }
 CLEAR (fmt);
 fmt.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;
// fmt.fmt.pix.width      = 640;
// fmt.fmt.pix.height      = 480;
 fmt.fmt.pix.width      = 320;
 fmt.fmt.pix.height      = 240;
 fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_JPEG;//V4L2_PIX_FMT_YUYV;//V4L2_PIX_FMT_YVU420;//V4L2_PIX_FMT_YUYV;
 fmt.fmt.pix.field      = V4L2_FIELD_INTERLACED;
 ff = ioctl (fd, VIDIOC_S_FMT, &fmt); //设置图像格式
 if(ff<0)
  printf("failture VIDIOC_S_FMT\n");
 file_length = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height; //计算图片大小

struct v4l2_requestbuffers req;
 CLEAR (req);
 req.count              = 1;
 req.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;
 req.memory              = V4L2_MEMORY_MMAP;

ff=ioctl (fd, VIDIOC_REQBUFS, &req); //申请缓冲，count是申请的数量
 if(ff<0)
  printf("failture VIDIOC_REQBUFS\n");
 if (req.count < 1)
  printf("Insufficient buffer memory\n");

buffers = calloc (req.count, sizeof (*buffers));//内存中建立对应空间