Documentation/DocBook/v4l/v4l2grab.c.xml

   1 <programlisting>
   2 /* V4L2 video picture grabber
   3    Copyright (C) 2009 Mauro Carvalho Chehab &lt;mchehab@infradead.org&gt;
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation version 2 of the License.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13  */
  14
  15 #include &lt;stdio.h&gt;
  16 #include &lt;stdlib.h&gt;
  17 #include &lt;string.h&gt;
  18 #include &lt;fcntl.h&gt;
  19 #include &lt;errno.h&gt;
  20 #include &lt;sys/ioctl.h&gt;
  21 #include &lt;sys/types.h&gt;
  22 #include &lt;sys/time.h&gt;
  23 #include &lt;sys/mman.h&gt;
  24 #include &lt;linux/videodev2.h&gt;
  25 #include "../libv4l/include/libv4l2.h"
  26
  27 #define CLEAR(x) memset(&amp;(x), 0, sizeof(x))
  28
  29 struct buffer {
  30         void   *start;
  31         size_t length;
  32 };
  33
  34 static void xioctl(int fh, int request, void *arg)
  35 {
  36         int r;
  37
  38         do {
  39                 r = v4l2_ioctl(fh, request, arg);
  40         } while (r == -1 &amp;&amp; ((errno == EINTR) || (errno == EAGAIN)));
  41
  42         if (r == -1) {
  43                 fprintf(stderr, "error %d, %s\n", errno, strerror(errno));
  44                 exit(EXIT_FAILURE);
  45         }
  46 }
  47
  48 int main(int argc, char **argv)
  49 {
  50         struct <link linkend="v4l2-format">v4l2_format</link>              fmt;
  51         struct <link linkend="v4l2-buffer">v4l2_buffer</link>              buf;
  52         struct <link linkend="v4l2-requestbuffers">v4l2_requestbuffers</link>      req;
  53         enum <link linkend="v4l2-buf-type">v4l2_buf_type</link>              type;
  54         fd_set                          fds;
  55         struct timeval                  tv;
  56         int                             r, fd = -1;
  57         unsigned int                    i, n_buffers;
  58         char                            *dev_name = "/dev/video0";
  59         char                            out_name[256];
  60         FILE                            *fout;
  61         struct buffer                   *buffers;
  62
  63         fd = v4l2_open(dev_name, O_RDWR | O_NONBLOCK, 0);
  64         if (fd &lt; 0) {
  65                 perror("Cannot open device");
  66                 exit(EXIT_FAILURE);
  67         }
  68
  69         CLEAR(fmt);
  70         fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  71         fmt.fmt.pix.width       = 640;
  72         fmt.fmt.pix.height      = 480;
  73         fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB24;
  74         fmt.fmt.pix.field       = V4L2_FIELD_INTERLACED;
  75         xioctl(fd, VIDIOC_S_FMT, &amp;fmt);
  76         if (fmt.fmt.pix.pixelformat != V4L2_PIX_FMT_RGB24) {
  77                 printf("Libv4l didn't accept RGB24 format. Can't proceed.\n");
  78                 exit(EXIT_FAILURE);
  79         }
  80         if ((fmt.fmt.pix.width != 640) || (fmt.fmt.pix.height != 480))
  81                 printf("Warning: driver is sending image at %dx%d\n",
  82                         fmt.fmt.pix.width, fmt.fmt.pix.height);
  83
  84         CLEAR(req);
  85         req.count = 2;
  86         req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  87         req.memory = V4L2_MEMORY_MMAP;
  88         xioctl(fd, VIDIOC_REQBUFS, &amp;req);
  89
  90         buffers = calloc(req.count, sizeof(*buffers));
  91         for (n_buffers = 0; n_buffers &lt; req.count; ++n_buffers) {
  92                 CLEAR(buf);
  93
  94                 buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  95                 buf.memory      = V4L2_MEMORY_MMAP;
  96                 buf.index       = n_buffers;
  97
  98                 xioctl(fd, VIDIOC_QUERYBUF, &amp;buf);
  99
 100                 buffers[n_buffers].length = buf.length;
 101                 buffers[n_buffers].start = v4l2_mmap(NULL, buf.length,
 102                               PROT_READ | PROT_WRITE, MAP_SHARED,
 103                               fd, buf.m.offset);
 104
 105                 if (MAP_FAILED == buffers[n_buffers].start) {
 106                         perror("mmap");
 107                         exit(EXIT_FAILURE);
 108                 }
 109         }
 110
 111         for (i = 0; i &lt; n_buffers; ++i) {
 112                 CLEAR(buf);
 113                 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
 114                 buf.memory = V4L2_MEMORY_MMAP;
 115                 buf.index = i;
 116                 xioctl(fd, VIDIOC_QBUF, &amp;buf);
 117         }
 118         type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
 119
 120         xioctl(fd, VIDIOC_STREAMON, &amp;type);
 121         for (i = 0; i &lt; 20; i++) {
 122                 do {
 123                         FD_ZERO(&amp;fds);
 124                         FD_SET(fd, &amp;fds);
 125
 126                         /* Timeout. */
 127                         tv.tv_sec = 2;
 128                         tv.tv_usec = 0;
 129
 130                         r = select(fd + 1, &amp;fds, NULL, NULL, &amp;tv);
 131                 } while ((r == -1 &amp;&amp; (errno = EINTR)));
 132                 if (r == -1) {
 133                         perror("select");
 134                         return errno;
 135                 }
 136
 137                 CLEAR(buf);
 138                 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
 139                 buf.memory = V4L2_MEMORY_MMAP;
 140                 xioctl(fd, VIDIOC_DQBUF, &amp;buf);
 141
 142                 sprintf(out_name, "out%03d.ppm", i);
 143                 fout = fopen(out_name, "w");
 144                 if (!fout) {
 145                         perror("Cannot open image");
 146                         exit(EXIT_FAILURE);
 147                 }
 148                 fprintf(fout, "P6\n%d %d 255\n",
 149                         fmt.fmt.pix.width, fmt.fmt.pix.height);
 150                 fwrite(buffers[buf.index].start, buf.bytesused, 1, fout);
 151                 fclose(fout);
 152
 153                 xioctl(fd, VIDIOC_QBUF, &amp;buf);
 154         }
 155
 156         type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
 157         xioctl(fd, VIDIOC_STREAMOFF, &amp;type);
 158         for (i = 0; i &lt; n_buffers; ++i)
 159                 v4l2_munmap(buffers[i].start, buffers[i].length);
 160         v4l2_close(fd);
 161
 162         return 0;
 163 }
 164 </programlisting>