//* WebCam access reference design using video4linux v2 *

/* * V4L2 video capture example * * This program can be used and distributed without restrictions. */ #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 <malloc.h> #include <sys/stat.h> #include <sys/types.h> #include <sys/time.h> #include <sys/mman.h> #include <sys/ioctl.h> #include <linux/types.h> /* for videodev2.h */ #include <linux/videodev2.h> #define CLEAR(x) memset (&(x), 0, sizeof (x)) typedef enum { IO_METHOD_READ, IO_METHOD_MMAP, IO_METHOD_USERPTR, } io_method; struct buffer { void * start; size_t length; }; static char * dev_name = NULL; static io_method io = IO_METHOD_MMAP; static int fd = -1; struct buffer * buffers = NULL; static unsigned int n_buffers = 0; 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 fd, int request, void * arg) { int r; do r = ioctl (fd, request, arg); while (-1 == r && EINTR == errno); return r; } static void process_image (const void * p) { fputc ('.', stdout); 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); 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); 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); if (-1 == xioctl (fd, VIDIOC_QBUF, &buf)) errno_exit ("VIDIOC_QBUF"); break; } return 1; } static void mainloop (void) { unsigned int count; count = 100; 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; unsigned int page_size; page_size = getpagesize (); buffer_size = (buffer_size + page_size - 1) & ~(page_size - 1); 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 = memalign (/* boundary */ page_size, 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; 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. */ /* 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" "Options:\n" "-d | --device name Video device name [/dev/video]\n" "-h | --help Print this message\n" "-m | --mmap Use memory mapped buffers\n" "-r | --read Use read() calls\n" "-u | --userp Use application allocated buffers\n" "", argv[0]); } static const char short_options [] = "d:hmru"; 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' }, { 0, 0, 0, 0 } }; int main (int argc, char ** argv) { dev_name = "/dev/video0"; for (;;) { int index; int c; c = getopt_long (argc, argv, short_options, long_options, &index); 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; default: usage (stderr, argc, argv); exit (EXIT_FAILURE); } } open_device (); init_device (); start_capturing (); mainloop (); stop_capturing (); uninit_device (); close_device (); exit (EXIT_SUCCESS); return 0; }