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v4l2grab.c

/* V4L2 video picture grabber
   Copyright (C) 2009 Mauro Carvalho Chehab <mchehab@infradead.org>

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
 */

#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 "../../lib/include/libv4l2.h"

#define CLEAR(x) memset(&(x), 0, sizeof(x))

struct buffer {
      void   *start;
      size_t length;
};

static void xioctl(int fh, unsigned long 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_RGB24;
      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 != 640) || (fmt.fmt.pix.height != 480))
            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);
      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);
            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;
}

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