Ubuntu10.04中利用V4L2读取摄像头数据并保存成文件【转】

转自：http://blog.chinaunix.net/uid-29339876-id-4042245.html

利用V4L2读取UVC摄像头数据并保存成视频文件，主要参考http://linuxtv.org/downloads/v4l-dvb-apis/index.html中的示例Appendix D. Video Capture Example，将读取的文件保存在当前目录下的file.yuv中，修改后的完成代码如下：

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/*
* V4L2 video capture example
* AUTHOT : WANGTISHENG
* DATA : 2013-12-18
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <getopt.h> /* getopt_long() */
#include <fcntl.h> /* low-level i/o */
#include <unistd.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>
#define CLEAR(x) memset(&(x), 0, sizeof(x))
struct buffer {
void *start;
size_t length;
};
static char *dev_name;
static int fd = -1; //DEVICE NUMBER
struct buffer *buffers;
static unsigned int n_buffers;
static int frame_count = 70;
FILE *fp; //FILE POINTOR
static void errno_exit(const char *s)
{
fprintf(stderr, "%s error %d, %s\n", s, errno, strerror(errno));
exit(EXIT_FAILURE);
}
static int xioctl(int fh, int request, void *arg)
{
int r;
do {
r = ioctl(fh, request, arg);
} while (-1 == r && EINTR == errno);
return r;
}
//处理函数
static void process_image(const void *p, int size)
{
fwrite(p,size, 1, fp);
}
static int read_frame(FILE *fp)
{
struct v4l2_buffer buf;
CLEAR(buf);
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf))
errno_exit("VIDIOC_DQBUF");
process_image(buffers[buf.index].start, buf.bytesused);
if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
errno_exit("VIDIOC_QBUF");
return 1;
}
static void mainloop(void)
{
unsigned int count;
count = frame_count;
while (count-- > 0) {
printf("No.%d\n",frame_count - count); //显示当前帧数目
read_frame(fp);
}
printf("\nREAD AND SAVE DONE!\n");
}
static void stop_capturing(void)
{
enum v4l2_buf_type type;
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (-1 == xioctl(fd, VIDIOC_STREAMOFF, &type))
errno_exit("VIDIOC_STREAMOFF");
}
static void start_capturing(void)
{
unsigned int i;
enum v4l2_buf_type type;
for (i = 0; i < n_buffers; ++i) {
struct v4l2_buffer buf;
CLEAR(buf);
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = i;
if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
errno_exit("VIDIOC_QBUF");
}
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (-1 == xioctl(fd, VIDIOC_STREAMON, &type))
errno_exit("VIDIOC_STREAMON");
}
static void uninit_device(void)
{
unsigned int i;
for (i = 0; i < n_buffers; ++i)
if (-1 == munmap(buffers[i].start, buffers[i].length))
errno_exit("munmap");
free(buffers);
}
static void init_mmap(void)
{
struct v4l2_requestbuffers req;
CLEAR(req);
req.count = 4;
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP;
if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) {
if (EINVAL == errno) {
fprintf(stderr, "%s does not support "
"memory mapping\n", dev_name);
exit(EXIT_FAILURE);
} else {
errno_exit("VIDIOC_REQBUFS");
}
}
if (req.count < 2) {
fprintf(stderr, "Insufficient buffer memory on %s\n",
dev_name);
exit(EXIT_FAILURE);
}
buffers = calloc(req.count, sizeof(*buffers));
if (!buffers) {
fprintf(stderr, "Out of memory\n");
exit(EXIT_FAILURE);
}
for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {
struct v4l2_buffer buf;
CLEAR(buf);
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = n_buffers;
if (-1 == xioctl(fd, VIDIOC_QUERYBUF, &buf))
errno_exit("VIDIOC_QUERYBUF");
buffers[n_buffers].length = buf.length;
buffers[n_buffers].start =
mmap(NULL /* start anywhere */,
buf.length,
PROT_READ | PROT_WRITE /* required */,
MAP_SHARED /* recommended */,
fd, buf.m.offset);
if (MAP_FAILED == buffers[n_buffers].start)
errno_exit("mmap");
}
}
static void init_device(void)
{
struct v4l2_capability cap;
struct v4l2_format fmt;
if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &cap)) { //测试参数
if (EINVAL == errno) {
fprintf(stderr, "%s is no V4L2 device\n",
dev_name);
exit(EXIT_FAILURE);
} else {
errno_exit("VIDIOC_QUERYCAP");
}
}
if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
fprintf(stderr, "%s is no video capture device\n",
dev_name);
exit(EXIT_FAILURE);
}
if (!(cap.capabilities & V4L2_CAP_STREAMING)) {
fprintf(stderr, "%s does not support streaming i/o\n",
dev_name);
exit(EXIT_FAILURE);
}
CLEAR(fmt);
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.width = 640;
fmt.fmt.pix.height = 480;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt)) //设置格式
errno_exit("VIDIOC_S_FMT");
init_mmap();
}
static void close_device(void)
{
if (-1 == close(fd))
errno_exit("close");
fd = -1;
}
static void open_device(void)
{
//加上O_NONBLOCK会出现如下错误
//VIDIOC_DQBUF error 11, Resource temporarily unavailable
fd = open(dev_name, O_RDWR /* required */ /*| O_NONBLOCK*/, 0);
if (-1 == fd) {
fprintf(stderr, "Cannot open '%s': %d, %s\n",
dev_name, errno, strerror(errno));
exit(EXIT_FAILURE);
}
}
int main(int argc, char **argv)
{
dev_name = "/dev/video0";
if(argc != 2)
{
printf("usage :%s filename\n", argv[0]);
exit(0);
}
if ((fp = fopen(argv[1], "w")) == NULL) {
perror("Creat file failed");
exit(0);
}
open_device();
init_device();
start_capturing();
mainloop(); //主要处理均在该函数中实现
fclose(fp);
stop_capturing();
uninit_device();
close_device();
//fprintf(stderr, "\n");
return 0;
}

Makefile

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v4l2_capture_example:v4l2_capture_example.c
gcc -Wall -o $@ $<
clean:
rm -rf v4l2_capture_example

make测试
运行方法
$ ./v4l2_capture_example file.yuv
可完成摄像头数据的读取和保存。附上查看YUV格式的软件一枚~~~~~~~
YUV_Tools.rar

巴特西

Ubuntu10.04中利用V4L2读取摄像头数据并保存成文件【转】

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