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June 11, 2021 05:29
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YUVで撮像してRGB24にconvertし、dumpするv4lプログラムの例
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// gcc -lv4l2 -lv4lconvert v4l_sample.c | |
#include <inttypes.h> | |
#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 "libv4lconvert.h" | |
#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) | |
{ | |
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 = 640; | |
fmt.fmt.pix.height = 480; | |
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV; | |
fmt.fmt.pix.field = V4L2_FIELD_INTERLACED; | |
xioctl(fd, VIDIOC_S_FMT, &fmt); | |
if (fmt.fmt.pix.pixelformat != V4L2_PIX_FMT_YUYV) { | |
printf("Libv4l didn't accept YUYV format. Can't proceed.\n"); | |
exit(EXIT_FAILURE); | |
} | |
if ((fmt.fmt.pix.width != 640) || (fmt.fmt.pix.height != 480)) | |
printf("Warning: driver is sending image at %dx%d\n", | |
fmt.fmt.pix.width, fmt.fmt.pix.height); | |
struct v4l2_streamparm parm; | |
CLEAR(parm); | |
parm.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; | |
parm.parm.capture.timeperframe.numerator = 1; | |
parm.parm.capture.timeperframe.denominator = 30; | |
parm.parm.capture.capturemode = V4L2_MODE_HIGHQUALITY; | |
xioctl(fd, VIDIOC_S_PARM, &parm); | |
CLEAR(req); | |
req.count = 4; | |
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); | |
} | |
} | |
struct v4lconvert_data * data = v4lconvert_create(fd); | |
struct v4l2_format dest_fmt; | |
CLEAR(dest_fmt); | |
dest_fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; | |
dest_fmt.fmt.pix.width = fmt.fmt.pix.width; | |
dest_fmt.fmt.pix.height = fmt.fmt.pix.height; | |
dest_fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB24; | |
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); | |
for (i = 0; i < 20; i++) { | |
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); | |
sprintf(out_name, "out%03d.ppm", i); | |
fout = fopen(out_name, "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); | |
int len = buf.length / 2 * 3; | |
void * img = calloc(len, sizeof(unsigned char)); | |
v4lconvert_convert(data, &fmt, &dest_fmt, | |
buffers[buf.index].start, buf.length, | |
img, len); | |
fwrite(img, len * sizeof(unsigned char), 1, fout); | |
free(img); | |
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; | |
} |
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