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Diffstat (limited to 'Documentation/userspace-api/media/v4l/v4l2grab.c.rst')
| -rw-r--r-- | Documentation/userspace-api/media/v4l/v4l2grab.c.rst | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/v4l/v4l2grab.c.rst b/Documentation/userspace-api/media/v4l/v4l2grab.c.rst new file mode 100644 index 000000000..1a55e3617 --- /dev/null +++ b/Documentation/userspace-api/media/v4l/v4l2grab.c.rst @@ -0,0 +1,169 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later + +file: media/v4l/v4l2grab.c +========================== + +.. code-block:: c + + /* V4L2 video picture grabber + Copyright (C) 2009 Mauro Carvalho Chehab <mchehab@kernel.org> + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation version 2 of the License. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + */ + + #include <stdio.h> + #include <stdlib.h> + #include <string.h> + #include <fcntl.h> + #include <errno.h> + #include <sys/ioctl.h> + #include <sys/types.h> + #include <sys/time.h> + #include <sys/mman.h> + #include <linux/videodev2.h> + #include "../libv4l/include/libv4l2.h" + + #define CLEAR(x) memset(&(x), 0, sizeof(x)) + + struct buffer { + void *start; + size_t length; + }; + + static void xioctl(int fh, int request, void *arg) + { + int r; + + do { + r = v4l2_ioctl(fh, request, arg); + } while (r == -1 && ((errno == EINTR) || (errno == EAGAIN))); + + if (r == -1) { + fprintf(stderr, "error %d, %s\n", errno, strerror(errno)); + exit(EXIT_FAILURE); + } + } + + int main(int argc, char **argv) + { + struct v4l2_format fmt; + struct v4l2_buffer buf; + struct v4l2_requestbuffers req; + enum v4l2_buf_type type; + fd_set fds; + struct timeval tv; + int r, fd = -1; + unsigned int i, n_buffers; + char *dev_name = "/dev/video0"; + char out_name[256]; + FILE *fout; + struct buffer *buffers; + + fd = v4l2_open(dev_name, O_RDWR | O_NONBLOCK, 0); + if (fd < 0) { + perror("Cannot open device"); + exit(EXIT_FAILURE); + } + + 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_RGB24; + fmt.fmt.pix.field = V4L2_FIELD_INTERLACED; + xioctl(fd, VIDIOC_S_FMT, &fmt); + if (fmt.fmt.pix.pixelformat != V4L2_PIX_FMT_RGB24) { + printf("Libv4l didn't accept RGB24 format. Can't proceed.\n"); + exit(EXIT_FAILURE); + } + if ((fmt.fmt.pix.width != 640) || (fmt.fmt.pix.height != 480)) + printf("Warning: driver is sending image at %dx%d\n", + fmt.fmt.pix.width, fmt.fmt.pix.height); + + CLEAR(req); + req.count = 2; + req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; + req.memory = V4L2_MEMORY_MMAP; + xioctl(fd, VIDIOC_REQBUFS, &req); + + buffers = calloc(req.count, sizeof(*buffers)); + for (n_buffers = 0; n_buffers < req.count; ++n_buffers) { + CLEAR(buf); + + buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; + buf.memory = V4L2_MEMORY_MMAP; + buf.index = n_buffers; + + xioctl(fd, VIDIOC_QUERYBUF, &buf); + + buffers[n_buffers].length = buf.length; + buffers[n_buffers].start = v4l2_mmap(NULL, buf.length, + PROT_READ | PROT_WRITE, MAP_SHARED, + fd, buf.m.offset); + + if (MAP_FAILED == buffers[n_buffers].start) { + perror("mmap"); + exit(EXIT_FAILURE); + } + } + + for (i = 0; i < n_buffers; ++i) { + CLEAR(buf); + buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; + buf.memory = V4L2_MEMORY_MMAP; + buf.index = i; + xioctl(fd, VIDIOC_QBUF, &buf); + } + type = V4L2_BUF_TYPE_VIDEO_CAPTURE; + + xioctl(fd, VIDIOC_STREAMON, &type); + for (i = 0; i < 20; i++) { + do { + FD_ZERO(&fds); + FD_SET(fd, &fds); + + /* Timeout. */ + tv.tv_sec = 2; + tv.tv_usec = 0; + + r = select(fd + 1, &fds, NULL, NULL, &tv); + } while ((r == -1 && (errno == EINTR))); + if (r == -1) { + perror("select"); + return errno; + } + + CLEAR(buf); + buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; + buf.memory = V4L2_MEMORY_MMAP; + xioctl(fd, VIDIOC_DQBUF, &buf); + + sprintf(out_name, "out%03d.ppm", i); + fout = fopen(out_name, "w"); + if (!fout) { + perror("Cannot open image"); + exit(EXIT_FAILURE); + } + fprintf(fout, "P6\n%d %d 255\n", + fmt.fmt.pix.width, fmt.fmt.pix.height); + fwrite(buffers[buf.index].start, buf.bytesused, 1, fout); + fclose(fout); + + xioctl(fd, VIDIOC_QBUF, &buf); + } + + type = V4L2_BUF_TYPE_VIDEO_CAPTURE; + xioctl(fd, VIDIOC_STREAMOFF, &type); + for (i = 0; i < n_buffers; ++i) + v4l2_munmap(buffers[i].start, buffers[i].length); + v4l2_close(fd); + + return 0; + } |