c_cpp v4l2网络摄像头捕获

Posted 2021-05-14

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <linux/videodev2.h>
#include <libv4l2.h>
#include <libv4l1.h>
/**
* A program to capture image via the camera. 
*
* @author Darran Zhang @ codelast.com
*/
#define CLEAR(x) memset(&(x), 0, sizeof(x))
struct buffer {
void   *start;
size_t length;
};
static void xioctl(int fh, int request, void *arg)
{
int r;
do {
r = v4l2_ioctl(fh, request, arg);
} while (r == -1 && ((errno == EINTR) || (errno == EAGAIN)));
if (r == -1) {
fprintf(stderr, "error %d, %s\n", errno, strerror(errno));
exit(EXIT_FAILURE);
}
}
int main(int argc, char **argv) {
if (argc < 4) {
printf("Usage: ./webcam [outputImagePath] [outputImageWidth] [outputImageHeight]\nE.g. ./webcam webcam.jpg 320 240\n");
return 1;
}
char* outputImagePath = argv[1];
int imageWidth = atoi(argv[2]);
int imageHeight = atoi(argv[3]);
struct v4l2_format              fmt;
struct v4l2_buffer              buf;
struct v4l2_requestbuffers      req;
enum v4l2_buf_type              type;
fd_set                          fds;
struct timeval                  tv;
int                             r, fd = -1;
unsigned int                    i, n_buffers;
char                            *dev_name = "/dev/video0";
char                            out_name[256];
FILE                            *fout;
struct buffer                   *buffers;
fd = v4l2_open(dev_name, O_RDWR | O_NONBLOCK, 0);
if (fd < 0) {
perror("Cannot open device");
exit(EXIT_FAILURE);
}
CLEAR(fmt);
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.width       = imageWidth;
fmt.fmt.pix.height      = imageHeight;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB24;
//fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_JPEG;
fmt.fmt.pix.field       = V4L2_FIELD_INTERLACED;
xioctl(fd, VIDIOC_S_FMT, &fmt);
if (fmt.fmt.pix.pixelformat != V4L2_PIX_FMT_RGB24) {
printf("Libv4l didn't accept RGB24 format. Can't proceed.\n");
exit(EXIT_FAILURE);
}
if ((fmt.fmt.pix.width != imageWidth) || (fmt.fmt.pix.height != imageHeight))
printf("Warning: driver is sending image at %dx%d\n", fmt.fmt.pix.width, fmt.fmt.pix.height);
CLEAR(req);
req.count = 2;
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP;
xioctl(fd, VIDIOC_REQBUFS, &req);
buffers = calloc(req.count, sizeof(*buffers));
for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {
CLEAR(buf);
buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory      = V4L2_MEMORY_MMAP;
buf.index       = n_buffers;
xioctl(fd, VIDIOC_QUERYBUF, &buf);
buffers[n_buffers].length = buf.length;
buffers[n_buffers].start = v4l2_mmap(NULL, buf.length,
PROT_READ | PROT_WRITE, MAP_SHARED,
fd, buf.m.offset);
if (MAP_FAILED == buffers[n_buffers].start) {
perror("mmap");
exit(EXIT_FAILURE);
}
}
for (i = 0; i < n_buffers; ++i) {
CLEAR(buf);
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = i;
xioctl(fd, VIDIOC_QBUF, &buf);
}
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
xioctl(fd, VIDIOC_STREAMON, &type);
do {
FD_ZERO(&fds);
FD_SET(fd, &fds);
/* Timeout. */
tv.tv_sec = 2;
tv.tv_usec = 0;
r = select(fd + 1, &fds, NULL, NULL, &tv);
} while ((r == -1 && (errno = EINTR)));
if (r == -1) {
perror("select");
return errno;
}
CLEAR(buf);
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
xioctl(fd, VIDIOC_DQBUF, &buf);
fout = fopen(outputImagePath, "w");
if (!fout) {
perror("Cannot open image");
exit(EXIT_FAILURE);
}
fprintf(fout, "P6\n%d %d 255\n",
fmt.fmt.pix.width, fmt.fmt.pix.height);
fwrite(buffers[buf.index].start, buf.bytesused, 1, fout);
fclose(fout);
xioctl(fd, VIDIOC_QBUF, &buf);
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
xioctl(fd, VIDIOC_STREAMOFF, &type);
for (i = 0; i < n_buffers; ++i) {
v4l2_munmap(buffers[i].start, buffers[i].length);
}
v4l2_close(fd);
return 0;
}