665 lines
15 KiB
ReStructuredText
665 lines
15 KiB
ReStructuredText
.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
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file: media/v4l/capture.c
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=========================
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.. code-block:: c
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/*
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* V4L2 video capture example
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*
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* This program can be used and distributed without restrictions.
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*
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* This program is provided with the V4L2 API
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* see https://linuxtv.org/docs.php for more information
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <assert.h>
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#include <getopt.h> /* getopt_long() */
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#include <fcntl.h> /* low-level i/o */
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#include <unistd.h>
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#include <errno.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <sys/time.h>
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#include <sys/mman.h>
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#include <sys/ioctl.h>
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#include <linux/videodev2.h>
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#define CLEAR(x) memset(&(x), 0, sizeof(x))
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enum io_method {
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IO_METHOD_READ,
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IO_METHOD_MMAP,
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IO_METHOD_USERPTR,
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};
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struct buffer {
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void *start;
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size_t length;
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};
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static char *dev_name;
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static enum io_method io = IO_METHOD_MMAP;
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static int fd = -1;
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struct buffer *buffers;
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static unsigned int n_buffers;
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static int out_buf;
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static int force_format;
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static int frame_count = 70;
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static void errno_exit(const char *s)
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{
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fprintf(stderr, "%s error %d, %s\n", s, errno, strerror(errno));
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exit(EXIT_FAILURE);
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}
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static int xioctl(int fh, int request, void *arg)
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{
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int r;
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do {
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r = ioctl(fh, request, arg);
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} while (-1 == r && EINTR == errno);
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return r;
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}
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static void process_image(const void *p, int size)
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{
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if (out_buf)
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fwrite(p, size, 1, stdout);
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fflush(stderr);
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fprintf(stderr, ".");
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fflush(stdout);
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}
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static int read_frame(void)
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{
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struct v4l2_buffer buf;
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unsigned int i;
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switch (io) {
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case IO_METHOD_READ:
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if (-1 == read(fd, buffers[0].start, buffers[0].length)) {
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switch (errno) {
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case EAGAIN:
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return 0;
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case EIO:
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/* Could ignore EIO, see spec. */
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/* fall through */
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default:
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errno_exit("read");
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}
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}
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process_image(buffers[0].start, buffers[0].length);
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break;
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case IO_METHOD_MMAP:
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CLEAR(buf);
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buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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buf.memory = V4L2_MEMORY_MMAP;
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if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf)) {
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switch (errno) {
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case EAGAIN:
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return 0;
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case EIO:
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/* Could ignore EIO, see spec. */
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/* fall through */
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default:
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errno_exit("VIDIOC_DQBUF");
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}
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}
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assert(buf.index < n_buffers);
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process_image(buffers[buf.index].start, buf.bytesused);
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if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
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errno_exit("VIDIOC_QBUF");
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break;
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case IO_METHOD_USERPTR:
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CLEAR(buf);
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buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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buf.memory = V4L2_MEMORY_USERPTR;
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if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf)) {
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switch (errno) {
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case EAGAIN:
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return 0;
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case EIO:
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/* Could ignore EIO, see spec. */
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/* fall through */
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default:
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errno_exit("VIDIOC_DQBUF");
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}
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}
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for (i = 0; i < n_buffers; ++i)
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if (buf.m.userptr == (unsigned long)buffers[i].start
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&& buf.length == buffers[i].length)
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break;
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assert(i < n_buffers);
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process_image((void *)buf.m.userptr, buf.bytesused);
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if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
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errno_exit("VIDIOC_QBUF");
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break;
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}
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return 1;
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}
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static void mainloop(void)
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{
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unsigned int count;
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count = frame_count;
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while (count-- > 0) {
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for (;;) {
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fd_set fds;
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struct timeval tv;
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int r;
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FD_ZERO(&fds);
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FD_SET(fd, &fds);
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/* Timeout. */
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tv.tv_sec = 2;
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tv.tv_usec = 0;
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r = select(fd + 1, &fds, NULL, NULL, &tv);
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if (-1 == r) {
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if (EINTR == errno)
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continue;
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errno_exit("select");
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}
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if (0 == r) {
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fprintf(stderr, "select timeout\n");
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exit(EXIT_FAILURE);
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}
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if (read_frame())
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break;
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/* EAGAIN - continue select loop. */
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}
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}
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}
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static void stop_capturing(void)
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{
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enum v4l2_buf_type type;
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switch (io) {
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case IO_METHOD_READ:
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/* Nothing to do. */
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break;
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case IO_METHOD_MMAP:
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case IO_METHOD_USERPTR:
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type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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if (-1 == xioctl(fd, VIDIOC_STREAMOFF, &type))
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errno_exit("VIDIOC_STREAMOFF");
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break;
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}
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}
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static void start_capturing(void)
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{
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unsigned int i;
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enum v4l2_buf_type type;
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switch (io) {
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case IO_METHOD_READ:
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/* Nothing to do. */
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break;
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case IO_METHOD_MMAP:
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for (i = 0; i < n_buffers; ++i) {
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struct v4l2_buffer buf;
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CLEAR(buf);
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buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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buf.memory = V4L2_MEMORY_MMAP;
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buf.index = i;
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if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
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errno_exit("VIDIOC_QBUF");
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}
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type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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if (-1 == xioctl(fd, VIDIOC_STREAMON, &type))
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errno_exit("VIDIOC_STREAMON");
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break;
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case IO_METHOD_USERPTR:
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for (i = 0; i < n_buffers; ++i) {
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struct v4l2_buffer buf;
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CLEAR(buf);
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buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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buf.memory = V4L2_MEMORY_USERPTR;
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buf.index = i;
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buf.m.userptr = (unsigned long)buffers[i].start;
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buf.length = buffers[i].length;
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if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
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errno_exit("VIDIOC_QBUF");
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}
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type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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if (-1 == xioctl(fd, VIDIOC_STREAMON, &type))
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errno_exit("VIDIOC_STREAMON");
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break;
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}
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}
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static void uninit_device(void)
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{
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unsigned int i;
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switch (io) {
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case IO_METHOD_READ:
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free(buffers[0].start);
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break;
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case IO_METHOD_MMAP:
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for (i = 0; i < n_buffers; ++i)
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if (-1 == munmap(buffers[i].start, buffers[i].length))
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errno_exit("munmap");
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break;
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case IO_METHOD_USERPTR:
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for (i = 0; i < n_buffers; ++i)
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free(buffers[i].start);
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break;
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}
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free(buffers);
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}
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static void init_read(unsigned int buffer_size)
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{
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buffers = calloc(1, sizeof(*buffers));
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if (!buffers) {
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fprintf(stderr, "Out of memory\n");
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exit(EXIT_FAILURE);
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}
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buffers[0].length = buffer_size;
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buffers[0].start = malloc(buffer_size);
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if (!buffers[0].start) {
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fprintf(stderr, "Out of memory\n");
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exit(EXIT_FAILURE);
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}
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}
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static void init_mmap(void)
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{
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struct v4l2_requestbuffers req;
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CLEAR(req);
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req.count = 4;
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req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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req.memory = V4L2_MEMORY_MMAP;
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if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) {
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if (EINVAL == errno) {
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fprintf(stderr, "%s does not support "
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"memory mappingn", dev_name);
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exit(EXIT_FAILURE);
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} else {
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errno_exit("VIDIOC_REQBUFS");
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}
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}
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if (req.count < 2) {
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fprintf(stderr, "Insufficient buffer memory on %s\n",
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dev_name);
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exit(EXIT_FAILURE);
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}
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buffers = calloc(req.count, sizeof(*buffers));
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if (!buffers) {
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fprintf(stderr, "Out of memory\n");
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exit(EXIT_FAILURE);
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}
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for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {
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struct v4l2_buffer buf;
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CLEAR(buf);
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buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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buf.memory = V4L2_MEMORY_MMAP;
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buf.index = n_buffers;
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if (-1 == xioctl(fd, VIDIOC_QUERYBUF, &buf))
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errno_exit("VIDIOC_QUERYBUF");
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buffers[n_buffers].length = buf.length;
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buffers[n_buffers].start =
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mmap(NULL /* start anywhere */,
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buf.length,
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PROT_READ | PROT_WRITE /* required */,
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MAP_SHARED /* recommended */,
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fd, buf.m.offset);
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if (MAP_FAILED == buffers[n_buffers].start)
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errno_exit("mmap");
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}
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}
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static void init_userp(unsigned int buffer_size)
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{
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struct v4l2_requestbuffers req;
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CLEAR(req);
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req.count = 4;
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req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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req.memory = V4L2_MEMORY_USERPTR;
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if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) {
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if (EINVAL == errno) {
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fprintf(stderr, "%s does not support "
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"user pointer i/on", dev_name);
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exit(EXIT_FAILURE);
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} else {
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errno_exit("VIDIOC_REQBUFS");
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}
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}
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buffers = calloc(4, sizeof(*buffers));
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if (!buffers) {
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fprintf(stderr, "Out of memory\n");
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exit(EXIT_FAILURE);
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}
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for (n_buffers = 0; n_buffers < 4; ++n_buffers) {
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buffers[n_buffers].length = buffer_size;
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buffers[n_buffers].start = malloc(buffer_size);
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if (!buffers[n_buffers].start) {
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fprintf(stderr, "Out of memory\n");
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exit(EXIT_FAILURE);
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}
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}
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}
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static void init_device(void)
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{
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struct v4l2_capability cap;
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struct v4l2_cropcap cropcap;
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struct v4l2_crop crop;
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struct v4l2_format fmt;
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unsigned int min;
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if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &cap)) {
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if (EINVAL == errno) {
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fprintf(stderr, "%s is no V4L2 device\n",
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dev_name);
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exit(EXIT_FAILURE);
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} else {
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errno_exit("VIDIOC_QUERYCAP");
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}
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}
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if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
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fprintf(stderr, "%s is no video capture device\n",
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dev_name);
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exit(EXIT_FAILURE);
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}
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switch (io) {
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case IO_METHOD_READ:
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if (!(cap.capabilities & V4L2_CAP_READWRITE)) {
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fprintf(stderr, "%s does not support read i/o\n",
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dev_name);
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exit(EXIT_FAILURE);
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}
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break;
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case IO_METHOD_MMAP:
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case IO_METHOD_USERPTR:
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if (!(cap.capabilities & V4L2_CAP_STREAMING)) {
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fprintf(stderr, "%s does not support streaming i/o\n",
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dev_name);
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exit(EXIT_FAILURE);
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}
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break;
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}
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/* Select video input, video standard and tune here. */
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CLEAR(cropcap);
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cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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if (0 == xioctl(fd, VIDIOC_CROPCAP, &cropcap)) {
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crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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crop.c = cropcap.defrect; /* reset to default */
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if (-1 == xioctl(fd, VIDIOC_S_CROP, &crop)) {
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switch (errno) {
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case EINVAL:
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/* Cropping not supported. */
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break;
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default:
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/* Errors ignored. */
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break;
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}
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}
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} else {
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/* Errors ignored. */
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}
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CLEAR(fmt);
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fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
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if (force_format) {
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fmt.fmt.pix.width = 640;
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fmt.fmt.pix.height = 480;
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fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
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fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
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if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))
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errno_exit("VIDIOC_S_FMT");
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/* Note VIDIOC_S_FMT may change width and height. */
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} else {
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/* Preserve original settings as set by v4l2-ctl for example */
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if (-1 == xioctl(fd, VIDIOC_G_FMT, &fmt))
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errno_exit("VIDIOC_G_FMT");
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}
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/* Buggy driver paranoia. */
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min = fmt.fmt.pix.width * 2;
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if (fmt.fmt.pix.bytesperline < min)
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fmt.fmt.pix.bytesperline = min;
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min = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height;
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if (fmt.fmt.pix.sizeimage < min)
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fmt.fmt.pix.sizeimage = min;
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switch (io) {
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case IO_METHOD_READ:
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init_read(fmt.fmt.pix.sizeimage);
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break;
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case IO_METHOD_MMAP:
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init_mmap();
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break;
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case IO_METHOD_USERPTR:
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init_userp(fmt.fmt.pix.sizeimage);
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break;
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}
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}
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static void close_device(void)
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{
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if (-1 == close(fd))
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errno_exit("close");
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fd = -1;
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}
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static void open_device(void)
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{
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struct stat st;
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if (-1 == stat(dev_name, &st)) {
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fprintf(stderr, "Cannot identify '%s': %d, %s\n",
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dev_name, errno, strerror(errno));
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exit(EXIT_FAILURE);
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}
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if (!S_ISCHR(st.st_mode)) {
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fprintf(stderr, "%s is no devicen", dev_name);
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exit(EXIT_FAILURE);
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}
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fd = open(dev_name, O_RDWR /* required */ | O_NONBLOCK, 0);
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if (-1 == fd) {
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fprintf(stderr, "Cannot open '%s': %d, %s\n",
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dev_name, errno, strerror(errno));
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exit(EXIT_FAILURE);
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}
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}
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static void usage(FILE *fp, int argc, char **argv)
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{
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fprintf(fp,
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"Usage: %s [options]\n\n"
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"Version 1.3\n"
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"Options:\n"
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"-d | --device name Video device name [%s]\n"
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"-h | --help Print this message\n"
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"-m | --mmap Use memory mapped buffers [default]\n"
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"-r | --read Use read() calls\n"
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"-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;
|
|
}
|