diff options
Diffstat (limited to 'Documentation/DocBook/media/v4l/capture.c.xml')
| -rw-r--r-- | Documentation/DocBook/media/v4l/capture.c.xml | 659 |
1 files changed, 659 insertions, 0 deletions
diff --git a/Documentation/DocBook/media/v4l/capture.c.xml b/Documentation/DocBook/media/v4l/capture.c.xml new file mode 100644 index 00000000..1c5c49a2 --- /dev/null +++ b/Documentation/DocBook/media/v4l/capture.c.xml @@ -0,0 +1,659 @@ +<programlisting> +/* + * 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, 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 <link linkend="v4l2-buffer">v4l2_buffer</link> 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 <link linkend="v4l2-buf-type">v4l2_buf_type</link> 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 <link linkend="v4l2-buf-type">v4l2_buf_type</link> type; + + switch (io) { + case IO_METHOD_READ: + /* Nothing to do. */ + break; + + case IO_METHOD_MMAP: + for (i = 0; i < n_buffers; ++i) { + struct <link linkend="v4l2-buffer">v4l2_buffer</link> 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 <link linkend="v4l2-buffer">v4l2_buffer</link> 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 <link linkend="v4l2-requestbuffers">v4l2_requestbuffers</link> 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 <link linkend="v4l2-buffer">v4l2_buffer</link> 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 <link linkend="v4l2-requestbuffers">v4l2_requestbuffers</link> 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 <link linkend="v4l2-capability">v4l2_capability</link> cap; + struct <link linkend="v4l2-cropcap">v4l2_cropcap</link> cropcap; + struct <link linkend="v4l2-crop">v4l2_crop</link> crop; + struct <link linkend="v4l2-format">v4l2_format</link> 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; +} +</programlisting> |