Documentation/media/uapi/v4l/v4l2grab.c.rst

   1 .. -*- coding: utf-8; mode: rst -*-
   2
   3 file: media/v4l/v4l2grab.c
   4 ==========================
   5
   6 .. code-block:: c
   7
   8     /* V4L2 video picture grabber
   9        Copyright (C) 2009 Mauro Carvalho Chehab <mchehab@infradead.org>
  10
  11        This program is free software; you can redistribute it and/or modify
  12        it under the terms of the GNU General Public License as published by
  13        the Free Software Foundation version 2 of the License.
  14
  15        This program is distributed in the hope that it will be useful,
  16        but WITHOUT ANY WARRANTY; without even the implied warranty of
  17        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18        GNU General Public License for more details.
  19      */
  20
  21     #include <stdio.h>
  22     #include <stdlib.h>
  23     #include <string.h>
  24     #include <fcntl.h>
  25     #include <errno.h>
  26     #include <sys/ioctl.h>
  27     #include <sys/types.h>
  28     #include <sys/time.h>
  29     #include <sys/mman.h>
  30     #include <linux/videodev2.h>
  31     #include "../libv4l/include/libv4l2.h"
  32
  33     #define CLEAR(x) memset(&(x), 0, sizeof(x))
  34
  35     struct buffer {
  36             void   *start;
  37             size_t length;
  38     };
  39
  40     static void xioctl(int fh, int request, void *arg)
  41     {
  42             int r;
  43
  44             do {
  45                     r = v4l2_ioctl(fh, request, arg);
  46             } while (r == -1 && ((errno == EINTR) || (errno == EAGAIN)));
  47
  48             if (r == -1) {
  49                     fprintf(stderr, "error %d, %s\\n", errno, strerror(errno));
  50                     exit(EXIT_FAILURE);
  51             }
  52     }
  53
  54     int main(int argc, char **argv)
  55     {
  56             struct v4l2_format              fmt;
  57             struct v4l2_buffer              buf;
  58             struct v4l2_requestbuffers      req;
  59             enum v4l2_buf_type              type;
  60             fd_set                          fds;
  61             struct timeval                  tv;
  62             int                             r, fd = -1;
  63             unsigned int                    i, n_buffers;
  64             char                            *dev_name = "/dev/video0";
  65             char                            out_name[256];
  66             FILE                            *fout;
  67             struct buffer                   *buffers;
  68
  69             fd = v4l2_open(dev_name, O_RDWR | O_NONBLOCK, 0);
  70             if (fd < 0) {
  71                     perror("Cannot open device");
  72                     exit(EXIT_FAILURE);
  73             }
  74
  75             CLEAR(fmt);
  76             fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  77             fmt.fmt.pix.width       = 640;
  78             fmt.fmt.pix.height      = 480;
  79             fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB24;
  80             fmt.fmt.pix.field       = V4L2_FIELD_INTERLACED;
  81             xioctl(fd, VIDIOC_S_FMT, &fmt);
  82             if (fmt.fmt.pix.pixelformat != V4L2_PIX_FMT_RGB24) {
  83                     printf("Libv4l didn't accept RGB24 format. Can't proceed.\\n");
  84                     exit(EXIT_FAILURE);
  85             }
  86             if ((fmt.fmt.pix.width != 640) || (fmt.fmt.pix.height != 480))
  87                     printf("Warning: driver is sending image at %dx%d\\n",
  88                             fmt.fmt.pix.width, fmt.fmt.pix.height);
  89
  90             CLEAR(req);
  91             req.count = 2;
  92             req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  93             req.memory = V4L2_MEMORY_MMAP;
  94             xioctl(fd, VIDIOC_REQBUFS, &req);
  95
  96             buffers = calloc(req.count, sizeof(*buffers));
  97             for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {
  98                     CLEAR(buf);
  99
 100                     buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE;
 101                     buf.memory      = V4L2_MEMORY_MMAP;
 102                     buf.index       = n_buffers;
 103
 104                     xioctl(fd, VIDIOC_QUERYBUF, &buf);
 105
 106                     buffers[n_buffers].length = buf.length;
 107                     buffers[n_buffers].start = v4l2_mmap(NULL, buf.length,
 108                                   PROT_READ | PROT_WRITE, MAP_SHARED,
 109                                   fd, buf.m.offset);
 110
 111                     if (MAP_FAILED == buffers[n_buffers].start) {
 112                             perror("mmap");
 113                             exit(EXIT_FAILURE);
 114                     }
 115             }
 116
 117             for (i = 0; i < n_buffers; ++i) {
 118                     CLEAR(buf);
 119                     buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
 120                     buf.memory = V4L2_MEMORY_MMAP;
 121                     buf.index = i;
 122                     xioctl(fd, VIDIOC_QBUF, &buf);
 123             }
 124             type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
 125
 126             xioctl(fd, VIDIOC_STREAMON, &type);
 127             for (i = 0; i < 20; i++) {
 128                     do {
 129                             FD_ZERO(&fds);
 130                             FD_SET(fd, &fds);
 131
 132                             /* Timeout. */
 133                             tv.tv_sec = 2;
 134                             tv.tv_usec = 0;
 135
 136                             r = select(fd + 1, &fds, NULL, NULL, &tv);
 137                     } while ((r == -1 && (errno = EINTR)));
 138                     if (r == -1) {
 139                             perror("select");
 140                             return errno;
 141                     }
 142
 143                     CLEAR(buf);
 144                     buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
 145                     buf.memory = V4L2_MEMORY_MMAP;
 146                     xioctl(fd, VIDIOC_DQBUF, &buf);
 147
 148                     sprintf(out_name, "out%03d.ppm", i);
 149                     fout = fopen(out_name, "w");
 150                     if (!fout) {
 151                             perror("Cannot open image");
 152                             exit(EXIT_FAILURE);
 153                     }
 154                     fprintf(fout, "P6\\n%d %d 255\\n",
 155                             fmt.fmt.pix.width, fmt.fmt.pix.height);
 156                     fwrite(buffers[buf.index].start, buf.bytesused, 1, fout);
 157                     fclose(fout);
 158
 159                     xioctl(fd, VIDIOC_QBUF, &buf);
 160             }
 161
 162             type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
 163             xioctl(fd, VIDIOC_STREAMOFF, &type);
 164             for (i = 0; i < n_buffers; ++i)
 165                     v4l2_munmap(buffers[i].start, buffers[i].length);
 166             v4l2_close(fd);
 167
 168             return 0;
 169     }