Logo Search packages:      
Sourcecode: v4l-utils version File versions  Download package

capture-example.c

/*
 *  V4L2 video capture example
 *
 *  This program can be used and distributed without restrictions.
 *
 *      This program is provided with the V4L2 API
 * see http://linuxtv.org/docs.php for more information
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

#include <getopt.h>             /* getopt_long() */

#include <fcntl.h>              /* low-level i/o */
#include <unistd.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <sys/ioctl.h>

#include <linux/videodev2.h>

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

enum io_method {
      IO_METHOD_READ,
      IO_METHOD_MMAP,
      IO_METHOD_USERPTR,
};

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

static char            *dev_name;
static enum io_method   io = IO_METHOD_MMAP;
static int              fd = -1;
struct buffer          *buffers;
static unsigned int     n_buffers;
static int        out_buf;
static int              force_format;
static int              frame_count = 70;

static void errno_exit(const char *s)
{
      fprintf(stderr, "%s error %d, %s\n", s, errno, strerror(errno));
      exit(EXIT_FAILURE);
}

static int xioctl(int fh, unsigned long int request, void *arg)
{
      int r;

      do {
            r = ioctl(fh, request, arg);
      } while (-1 == r && EINTR == errno);

      return r;
}

static void process_image(const void *p, int size)
{
      if (out_buf)
            fwrite(p, size, 1, stdout);

      fflush(stderr);
      fprintf(stderr, ".");
      fflush(stdout);
}

static int read_frame(void)
{
      struct v4l2_buffer buf;
      unsigned int i;

      switch (io) {
      case IO_METHOD_READ:
            if (-1 == read(fd, buffers[0].start, buffers[0].length)) {
                  switch (errno) {
                  case EAGAIN:
                        return 0;

                  case EIO:
                        /* Could ignore EIO, see spec. */

                        /* fall through */

                  default:
                        errno_exit("read");
                  }
            }

            process_image(buffers[0].start, buffers[0].length);
            break;

      case IO_METHOD_MMAP:
            CLEAR(buf);

            buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
            buf.memory = V4L2_MEMORY_MMAP;

            if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf)) {
                  switch (errno) {
                  case EAGAIN:
                        return 0;

                  case EIO:
                        /* Could ignore EIO, see spec. */

                        /* fall through */

                  default:
                        errno_exit("VIDIOC_DQBUF");
                  }
            }

            assert(buf.index < n_buffers);

            process_image(buffers[buf.index].start, buf.bytesused);

            if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
                  errno_exit("VIDIOC_QBUF");
            break;

      case IO_METHOD_USERPTR:
            CLEAR(buf);

            buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
            buf.memory = V4L2_MEMORY_USERPTR;

            if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf)) {
                  switch (errno) {
                  case EAGAIN:
                        return 0;

                  case EIO:
                        /* Could ignore EIO, see spec. */

                        /* fall through */

                  default:
                        errno_exit("VIDIOC_DQBUF");
                  }
            }

            for (i = 0; i < n_buffers; ++i)
                  if (buf.m.userptr == (unsigned long)buffers[i].start
                      && buf.length == buffers[i].length)
                        break;

            assert(i < n_buffers);

            process_image((void *)buf.m.userptr, buf.bytesused);

            if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
                  errno_exit("VIDIOC_QBUF");
            break;
      }

      return 1;
}

static void mainloop(void)
{
      unsigned int count;

      count = frame_count;

      while (count-- > 0) {
            for (;;) {
                  fd_set fds;
                  struct timeval tv;
                  int r;

                  FD_ZERO(&fds);
                  FD_SET(fd, &fds);

                  /* Timeout. */
                  tv.tv_sec = 2;
                  tv.tv_usec = 0;

                  r = select(fd + 1, &fds, NULL, NULL, &tv);

                  if (-1 == r) {
                        if (EINTR == errno)
                              continue;
                        errno_exit("select");
                  }

                  if (0 == r) {
                        fprintf(stderr, "select timeout\n");
                        exit(EXIT_FAILURE);
                  }

                  if (read_frame())
                        break;
                  /* EAGAIN - continue select loop. */
            }
      }
}

static void stop_capturing(void)
{
      enum v4l2_buf_type type;

      switch (io) {
      case IO_METHOD_READ:
            /* Nothing to do. */
            break;

      case IO_METHOD_MMAP:
      case IO_METHOD_USERPTR:
            type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
            if (-1 == xioctl(fd, VIDIOC_STREAMOFF, &type))
                  errno_exit("VIDIOC_STREAMOFF");
            break;
      }
}

static void start_capturing(void)
{
      unsigned int i;
      enum v4l2_buf_type type;

      switch (io) {
      case IO_METHOD_READ:
            /* Nothing to do. */
            break;

      case IO_METHOD_MMAP:
            for (i = 0; i < n_buffers; ++i) {
                  struct v4l2_buffer buf;

                  CLEAR(buf);
                  buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
                  buf.memory = V4L2_MEMORY_MMAP;
                  buf.index = i;

                  if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
                        errno_exit("VIDIOC_QBUF");
            }
            type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
            if (-1 == xioctl(fd, VIDIOC_STREAMON, &type))
                  errno_exit("VIDIOC_STREAMON");
            break;

      case IO_METHOD_USERPTR:
            for (i = 0; i < n_buffers; ++i) {
                  struct v4l2_buffer buf;

                  CLEAR(buf);
                  buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
                  buf.memory = V4L2_MEMORY_USERPTR;
                  buf.index = i;
                  buf.m.userptr = (unsigned long)buffers[i].start;
                  buf.length = buffers[i].length;

                  if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
                        errno_exit("VIDIOC_QBUF");
            }
            type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
            if (-1 == xioctl(fd, VIDIOC_STREAMON, &type))
                  errno_exit("VIDIOC_STREAMON");
            break;
      }
}

static void uninit_device(void)
{
      unsigned int i;

      switch (io) {
      case IO_METHOD_READ:
            free(buffers[0].start);
            break;

      case IO_METHOD_MMAP:
            for (i = 0; i < n_buffers; ++i)
                  if (-1 == munmap(buffers[i].start, buffers[i].length))
                        errno_exit("munmap");
            break;

      case IO_METHOD_USERPTR:
            for (i = 0; i < n_buffers; ++i)
                  free(buffers[i].start);
            break;
      }

      free(buffers);
}

static void init_read(unsigned int buffer_size)
{
      buffers = calloc(1, sizeof(*buffers));

      if (!buffers) {
            fprintf(stderr, "Out of memory\n");
            exit(EXIT_FAILURE);
      }

      buffers[0].length = buffer_size;
      buffers[0].start = malloc(buffer_size);

      if (!buffers[0].start) {
            fprintf(stderr, "Out of memory\n");
            exit(EXIT_FAILURE);
      }
}

static void init_mmap(void)
{
      struct v4l2_requestbuffers req;

      CLEAR(req);

      req.count = 4;
      req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
      req.memory = V4L2_MEMORY_MMAP;

      if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) {
            if (EINVAL == errno) {
                  fprintf(stderr, "%s does not support "
                         "memory mapping\n", dev_name);
                  exit(EXIT_FAILURE);
            } else {
                  errno_exit("VIDIOC_REQBUFS");
            }
      }

      if (req.count < 2) {
            fprintf(stderr, "Insufficient buffer memory on %s\n",
                   dev_name);
            exit(EXIT_FAILURE);
      }

      buffers = calloc(req.count, sizeof(*buffers));

      if (!buffers) {
            fprintf(stderr, "Out of memory\n");
            exit(EXIT_FAILURE);
      }

      for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {
            struct v4l2_buffer buf;

            CLEAR(buf);

            buf.type        = V4L2_BUF_TYPE_VIDEO_CAPTURE;
            buf.memory      = V4L2_MEMORY_MMAP;
            buf.index       = n_buffers;

            if (-1 == xioctl(fd, VIDIOC_QUERYBUF, &buf))
                  errno_exit("VIDIOC_QUERYBUF");

            buffers[n_buffers].length = buf.length;
            buffers[n_buffers].start =
                  mmap(NULL /* start anywhere */,
                        buf.length,
                        PROT_READ | PROT_WRITE /* required */,
                        MAP_SHARED /* recommended */,
                        fd, buf.m.offset);

            if (MAP_FAILED == buffers[n_buffers].start)
                  errno_exit("mmap");
      }
}

static void init_userp(unsigned int buffer_size)
{
      struct v4l2_requestbuffers req;

      CLEAR(req);

      req.count  = 4;
      req.type   = V4L2_BUF_TYPE_VIDEO_CAPTURE;
      req.memory = V4L2_MEMORY_USERPTR;

      if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) {
            if (EINVAL == errno) {
                  fprintf(stderr, "%s does not support "
                         "user pointer i/o\n", dev_name);
                  exit(EXIT_FAILURE);
            } else {
                  errno_exit("VIDIOC_REQBUFS");
            }
      }

      buffers = calloc(4, sizeof(*buffers));

      if (!buffers) {
            fprintf(stderr, "Out of memory\n");
            exit(EXIT_FAILURE);
      }

      for (n_buffers = 0; n_buffers < 4; ++n_buffers) {
            buffers[n_buffers].length = buffer_size;
            buffers[n_buffers].start = malloc(buffer_size);

            if (!buffers[n_buffers].start) {
                  fprintf(stderr, "Out of memory\n");
                  exit(EXIT_FAILURE);
            }
      }
}

static void init_device(void)
{
      struct v4l2_capability cap;
      struct v4l2_cropcap cropcap;
      struct v4l2_crop crop;
      struct v4l2_format fmt;
      unsigned int min;

      if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &cap)) {
            if (EINVAL == errno) {
                  fprintf(stderr, "%s is no V4L2 device\n",
                         dev_name);
                  exit(EXIT_FAILURE);
            } else {
                  errno_exit("VIDIOC_QUERYCAP");
            }
      }

      if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
            fprintf(stderr, "%s is no video capture device\n",
                   dev_name);
            exit(EXIT_FAILURE);
      }

      switch (io) {
      case IO_METHOD_READ:
            if (!(cap.capabilities & V4L2_CAP_READWRITE)) {
                  fprintf(stderr, "%s does not support read i/o\n",
                         dev_name);
                  exit(EXIT_FAILURE);
            }
            break;

      case IO_METHOD_MMAP:
      case IO_METHOD_USERPTR:
            if (!(cap.capabilities & V4L2_CAP_STREAMING)) {
                  fprintf(stderr, "%s does not support streaming i/o\n",
                         dev_name);
                  exit(EXIT_FAILURE);
            }
            break;
      }


      /* Select video input, video standard and tune here. */


      CLEAR(cropcap);

      cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

      if (0 == xioctl(fd, VIDIOC_CROPCAP, &cropcap)) {
            crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
            crop.c = cropcap.defrect; /* reset to default */

            if (-1 == xioctl(fd, VIDIOC_S_CROP, &crop)) {
                  switch (errno) {
                  case EINVAL:
                        /* Cropping not supported. */
                        break;
                  default:
                        /* Errors ignored. */
                        break;
                  }
            }
      } else {
            /* Errors ignored. */
      }


      CLEAR(fmt);

      fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
      if (force_format) {
            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;

            if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))
                  errno_exit("VIDIOC_S_FMT");

            /* Note VIDIOC_S_FMT may change width and height. */
      } else {
            /* Preserve original settings as set by v4l2-ctl for example */
            if (-1 == xioctl(fd, VIDIOC_G_FMT, &fmt))
                  errno_exit("VIDIOC_G_FMT");
      }

      /* Buggy driver paranoia. */
      min = fmt.fmt.pix.width * 2;
      if (fmt.fmt.pix.bytesperline < min)
            fmt.fmt.pix.bytesperline = min;
      min = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height;
      if (fmt.fmt.pix.sizeimage < min)
            fmt.fmt.pix.sizeimage = min;

      switch (io) {
      case IO_METHOD_READ:
            init_read(fmt.fmt.pix.sizeimage);
            break;

      case IO_METHOD_MMAP:
            init_mmap();
            break;

      case IO_METHOD_USERPTR:
            init_userp(fmt.fmt.pix.sizeimage);
            break;
      }
}

static void close_device(void)
{
      if (-1 == close(fd))
            errno_exit("close");

      fd = -1;
}

static void open_device(void)
{
      struct stat st;

      if (-1 == stat(dev_name, &st)) {
            fprintf(stderr, "Cannot identify '%s': %d, %s\n",
                   dev_name, errno, strerror(errno));
            exit(EXIT_FAILURE);
      }

      if (!S_ISCHR(st.st_mode)) {
            fprintf(stderr, "%s is no device\n", dev_name);
            exit(EXIT_FAILURE);
      }

      fd = open(dev_name, O_RDWR /* required */ | O_NONBLOCK, 0);

      if (-1 == fd) {
            fprintf(stderr, "Cannot open '%s': %d, %s\n",
                   dev_name, errno, strerror(errno));
            exit(EXIT_FAILURE);
      }
}

static void usage(FILE *fp, int argc, char **argv)
{
      fprintf(fp,
             "Usage: %s [options]\n\n"
             "Version 1.3\n"
             "Options:\n"
             "-d | --device name   Video device name [%s]\n"
             "-h | --help          Print this message\n"
             "-m | --mmap          Use memory mapped buffers [default]\n"
             "-r | --read          Use read() calls\n"
             "-u | --userp         Use application allocated buffers\n"
             "-o | --output        Outputs stream to stdout\n"
             "-f | --format        Force format to 640x480 YUYV\n"
             "-c | --count         Number of frames to grab [%i]\n"
             "",
             argv[0], dev_name, frame_count);
}

static const char short_options[] = "d:hmruofc:";

static const struct option
long_options[] = {
      { "device", required_argument, NULL, 'd' },
      { "help",   no_argument,       NULL, 'h' },
      { "mmap",   no_argument,       NULL, 'm' },
      { "read",   no_argument,       NULL, 'r' },
      { "userp",  no_argument,       NULL, 'u' },
      { "output", no_argument,       NULL, 'o' },
      { "format", no_argument,       NULL, 'f' },
      { "count",  required_argument, NULL, 'c' },
      { 0, 0, 0, 0 }
};

int main(int argc, char **argv)
{
      dev_name = "/dev/video0";

      for (;;) {
            int idx;
            int c;

            c = getopt_long(argc, argv,
                        short_options, long_options, &idx);

            if (-1 == c)
                  break;

            switch (c) {
            case 0: /* getopt_long() flag */
                  break;

            case 'd':
                  dev_name = optarg;
                  break;

            case 'h':
                  usage(stdout, argc, argv);
                  exit(EXIT_SUCCESS);

            case 'm':
                  io = IO_METHOD_MMAP;
                  break;

            case 'r':
                  io = IO_METHOD_READ;
                  break;

            case 'u':
                  io = IO_METHOD_USERPTR;
                  break;

            case 'o':
                  out_buf++;
                  break;

            case 'f':
                  force_format++;
                  break;

            case 'c':
                  errno = 0;
                  frame_count = strtol(optarg, NULL, 0);
                  if (errno)
                        errno_exit(optarg);
                  break;

            default:
                  usage(stderr, argc, argv);
                  exit(EXIT_FAILURE);
            }
      }

      open_device();
      init_device();
      start_capturing();
      mainloop();
      stop_capturing();
      uninit_device();
      close_device();
      fprintf(stderr, "\n");
      return 0;
}

Generated by  Doxygen 1.6.0   Back to index