1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2
3 file: media/v4l/v4l2grab.c
4 ==========================
5
6 .. code-block:: c
7
8 /* V4L2 video picture grabber
9 Copyright (C) 2009 Mauro Carvalho Chehab <mchehab@kernel.org>
10
11 This program is free software; you can redistribute it and/or modify
12 it under the terms of the GNU General Public License as published by
13 the Free Software Foundation version 2 of the License.
14
15 This program is distributed in the hope that it will be useful,
16 but WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 GNU General Public License for more details.
19 */
20
21 #include <stdio.h>
22 #include <stdlib.h>
23 #include <string.h>
24 #include <fcntl.h>
25 #include <errno.h>
26 #include <sys/ioctl.h>
27 #include <sys/types.h>
28 #include <sys/time.h>
29 #include <sys/mman.h>
30 #include <linux/videodev2.h>
31 #include "../libv4l/include/libv4l2.h"
32
33 #define CLEAR(x) memset(&(x), 0, sizeof(x))
34
35 struct buffer {
36 void *start;
37 size_t length;
38 };
39
40 static void xioctl(int fh, int request, void *arg)
41 {
42 int r;
43
44 do {
45 r = v4l2_ioctl(fh, request, arg);
46 } while (r == -1 && ((errno == EINTR) || (errno == EAGAIN)));
47
48 if (r == -1) {
49 fprintf(stderr, "error %d, %s\n", errno, strerror(errno));
50 exit(EXIT_FAILURE);
51 }
52 }
53
54 int main(int argc, char **argv)
55 {
56 struct v4l2_format fmt;
57 struct v4l2_buffer buf;
58 struct v4l2_requestbuffers req;
59 enum v4l2_buf_type type;
60 fd_set fds;
61 struct timeval tv;
62 int r, fd = -1;
63 unsigned int i, n_buffers;
64 char *dev_name = "/dev/video0";
65 char out_name[256];
66 FILE *fout;
67 struct buffer *buffers;
68
69 fd = v4l2_open(dev_name, O_RDWR | O_NONBLOCK, 0);
70 if (fd < 0) {
71 perror("Cannot open device");
72 exit(EXIT_FAILURE);
73 }
74
75 CLEAR(fmt);
76 fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
77 fmt.fmt.pix.width = 640;
78 fmt.fmt.pix.height = 480;
79 fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB24;
80 fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
81 xioctl(fd, VIDIOC_S_FMT, &fmt);
82 if (fmt.fmt.pix.pixelformat != V4L2_PIX_FMT_RGB24) {
83 printf("Libv4l didn't accept RGB24 format. Can't proceed.\n");
84 exit(EXIT_FAILURE);
85 }
86 if ((fmt.fmt.pix.width != 640) || (fmt.fmt.pix.height != 480))
87 printf("Warning: driver is sending image at %dx%d\n",
88 fmt.fmt.pix.width, fmt.fmt.pix.height);
89
90 CLEAR(req);
91 req.count = 2;
92 req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
93 req.memory = V4L2_MEMORY_MMAP;
94 xioctl(fd, VIDIOC_REQBUFS, &req);
95
96 buffers = calloc(req.count, sizeof(*buffers));
97 for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {
98 CLEAR(buf);
99
100 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
101 buf.memory = V4L2_MEMORY_MMAP;
102 buf.index = n_buffers;
103
104 xioctl(fd, VIDIOC_QUERYBUF, &buf);
105
106 buffers[n_buffers].length = buf.length;
107 buffers[n_buffers].start = v4l2_mmap(NULL, buf.length,
108 PROT_READ | PROT_WRITE, MAP_SHARED,
109 fd, buf.m.offset);
110
111 if (MAP_FAILED == buffers[n_buffers].start) {
112 perror("mmap");
113 exit(EXIT_FAILURE);
114 }
115 }
116
117 for (i = 0; i < n_buffers; ++i) {
118 CLEAR(buf);
119 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
120 buf.memory = V4L2_MEMORY_MMAP;
121 buf.index = i;
122 xioctl(fd, VIDIOC_QBUF, &buf);
123 }
124 type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
125
126 xioctl(fd, VIDIOC_STREAMON, &type);
127 for (i = 0; i < 20; i++) {
128 do {
129 FD_ZERO(&fds);
130 FD_SET(fd, &fds);
131
132 /* Timeout. */
133 tv.tv_sec = 2;
134 tv.tv_usec = 0;
135
136 r = select(fd + 1, &fds, NULL, NULL, &tv);
137 } while ((r == -1 && (errno == EINTR)));
138 if (r == -1) {
139 perror("select");
140 return errno;
141 }
142
143 CLEAR(buf);
144 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
145 buf.memory = V4L2_MEMORY_MMAP;
146 xioctl(fd, VIDIOC_DQBUF, &buf);
147
148 sprintf(out_name, "out%03d.ppm", i);
149 fout = fopen(out_name, "w");
150 if (!fout) {
151 perror("Cannot open image");
152 exit(EXIT_FAILURE);
153 }
154 fprintf(fout, "P6\n%d %d 255\n",
155 fmt.fmt.pix.width, fmt.fmt.pix.height);
156 fwrite(buffers[buf.index].start, buf.bytesused, 1, fout);
157 fclose(fout);
158
159 xioctl(fd, VIDIOC_QBUF, &buf);
160 }
161
162 type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
163 xioctl(fd, VIDIOC_STREAMOFF, &type);
164 for (i = 0; i < n_buffers; ++i)
165 v4l2_munmap(buffers[i].start, buffers[i].length);
166 v4l2_close(fd);
167
168 return 0;
169 }
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