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
#include
#include
#include

#include

#include
#include
#include
#include
#include
#include
#include
#include
#include

#include
#include

#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

for (n_buffers = 0; n_buffers < req.count; ++n_buffers)
{
struct v4l2_buffer buf; //驱动中的一帧
CLEAR (buf);
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = n_buffers;

if (-1 == ioctl (fd, VIDIOC_QUERYBUF, &buf)) //映射用户空间
printf ("VIDIOC_QUERYBUF error\n");