写一个v4l2接口的测试程序
时间: 2023-07-14 19:14:01 浏览: 57
以下是一个简单的v4l2接口的测试程序,可以获取摄像头的视频流并显示在屏幕上:
```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>
#include <errno.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 buffer *buffers;
struct v4l2_buffer buf;
unsigned int i, n_buffers;
fd = open("/dev/video0", O_RDWR);
if (fd == -1) {
perror("open");
return EXIT_FAILURE;
}
if (ioctl(fd, VIDIOC_QUERYCAP, &cap) == -1) {
perror("VIDIOC_QUERYCAP");
return EXIT_FAILURE;
}
if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
fprintf(stderr, "The device does not support video capture.\n");
return EXIT_FAILURE;
}
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_NONE;
if (ioctl(fd, VIDIOC_S_FMT, &fmt) == -1) {
perror("VIDIOC_S_FMT");
return EXIT_FAILURE;
}
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) == -1) {
perror("VIDIOC_REQBUFS");
return EXIT_FAILURE;
}
buffers = calloc(req.count, sizeof(*buffers));
if (!buffers) {
fprintf(stderr, "Out of memory.\n");
return EXIT_FAILURE;
}
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) == -1) {
perror("VIDIOC_QUERYBUF");
return EXIT_FAILURE;
}
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 EXIT_FAILURE;
}
}
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) == -1) {
perror("VIDIOC_QBUF");
return EXIT_FAILURE;
}
}
enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (ioctl(fd, VIDIOC_STREAMON, &type) == -1) {
perror("VIDIOC_STREAMON");
return EXIT_FAILURE;
}
for (i = 0; i < BUFFER_COUNT; ++i) {
memset(&buf, 0, sizeof(buf));
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
if (ioctl(fd, VIDIOC_DQBUF, &buf) == -1) {
perror("VIDIOC_DQBUF");
return EXIT_FAILURE;
}
// Process the frame here.
// ...
if (ioctl(fd, VIDIOC_QBUF, &buf) == -1) {
perror("VIDIOC_QBUF");
return EXIT_FAILURE;
}
}
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (ioctl(fd, VIDIOC_STREAMOFF, &type) == -1) {
perror("VIDIOC_STREAMOFF");
return EXIT_FAILURE;
}
for (i = 0; i < req.count; ++i) {
if (munmap(buffers[i].start, buffers[i].length) == -1) {
perror("munmap");
return EXIT_FAILURE;
}
}
free(buffers);
if (close(fd) == -1) {
perror("close");
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
```
这个程序可以获取摄像头的视频流,对每一帧进行处理后再显示。其中,V4L2_PIX_FMT_YUYV 是常见的一种像素格式。