你可以帮我写个v4l2框架的camera取流代码
时间: 2023-05-21 07:02:04 浏览: 97
当然可以,以下是一个简单的v4l2框架的camera取流代码示例:
```c++
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <linux/videodev2.h>
#define BUFFER_COUNT 4
struct buffer {
void *start;
size_t length;
};
int main(int argc, char **argv) {
int fd;
struct v4l2_capability cap;
struct v4l2_format fmt;
struct v4l2_requestbuffers req;
struct v4l2_buffer buf;
enum v4l2_buf_type type;
struct buffer buffers[BUFFER_COUNT];
unsigned int i, n;
fd_set fds;
struct timeval tv;
int r;
fd = open("/dev/video0", O_RDWR);
if (fd < 0) {
perror("open");
return 1;
}
if (ioctl(fd, VIDIOC_QUERYCAP, &cap) < 0) {
perror("VIDIOC_QUERYCAP");
return 1;
}
if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
fprintf(stderr, "The device does not support video capture.\n");
return 1;
}
if (!(cap.capabilities & V4L2_CAP_STREAMING)) {
fprintf(stderr, "The device does not support streaming I/O.\n");
return 1;
}
memset(&fmt, 0, sizeof(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 (ioctl(fd, VIDIOC_S_FMT, &fmt) < 0) {
perror("VIDIOC_S_FMT");
return 1;
}
memset(&req, 0, sizeof(req));
req.count = BUFFER_COUNT;
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP;
if (ioctl(fd, VIDIOC_REQBUFS, &req) < 0) {
perror("VIDIOC_REQBUFS");
return 1;
}
for (i = 0; i < req.count; i++) {
memset(&buf, 0, sizeof(buf));
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = i;
if (ioctl(fd, VIDIOC_QUERYBUF, &buf) < 0) {
perror("VIDIOC_QUERYBUF");
return 1;
}
buffers[i].length = buf.length;
buffers[i].start = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, fd, buf.m.offset);
if (buffers[i].start == MAP_FAILED) {
perror("mmap");
return 1;
}
}
for (i = 0; i < req.count; i++) {
memset(&buf, 0, sizeof(buf));
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = i;
if (ioctl(fd, VIDIOC_QBUF, &buf) < 0) {
perror("VIDIOC_QBUF");
return 1;
}
}
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (ioctl(fd, VIDIOC_STREAMON, &type) < 0) {
perror("VIDIOC_STREAMON");
return 1;
}
for (n = 0; n < 100; n++) {
FD_ZERO(&fds);
FD_SET(fd, &fds);
tv.tv_sec = 2;
tv.tv_usec = 0;
r = select(fd + 1, &fds, NULL, NULL, &tv);
if (r < 0) {
perror("select");
return 1;
}
if (r == 0) {
fprintf(stderr, "select timeout\n");
return 1;
}
memset(&buf, 0, sizeof(buf));
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
if (ioctl(fd, VIDIOC_DQBUF, &buf) < 0) {
perror("VIDIOC_DQBUF");
return 1;
}
printf("frame %u: %p\n", n, buffers[buf.index].start);
if (ioctl(fd, VIDIOC_QBUF, &buf) < 0) {
perror("VIDIOC_QBUF");
return 1;
}
}
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (ioctl(fd, VIDIOC_STREAMOFF, &type) < 0) {
perror("VIDIOC_STREAMOFF");
return 1;
}
for (i = 0; i < req.count; i++) {
if (munmap(buffers[i].start, buffers[i].length) < 0) {
perror("munmap");
return 1;
}
}
close(fd);
return 0;
}
```
这段代码使用了v4l2框架来获取摄像头的视频流数据。它首先通过ioctl函数查询设备的能力,然后设置视频格式和请求缓冲区。接着,它使用mmap函数将缓冲区映射到用户空间,然后将缓冲区加入到队列中。最后,它使用select函数等待摄像头的数据,并将数据从队列中取出,处理完后再将缓冲区重新加入队列。