tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1<programlisting>
2/* V4L2 video picture grabber
3 Copyright (C) 2009 Mauro Carvalho Chehab <mchehab@infradead.org>
4
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation version 2 of the License.
8
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
13 */
14
15#include <stdio.h>
16#include <stdlib.h>
17#include <string.h>
18#include <fcntl.h>
19#include <errno.h>
20#include <sys/ioctl.h>
21#include <sys/types.h>
22#include <sys/time.h>
23#include <sys/mman.h>
24#include <linux/videodev2.h>
25#include "../libv4l/include/libv4l2.h"
26
27#define CLEAR(x) memset(&(x), 0, sizeof(x))
28
29struct buffer {
30 void *start;
31 size_t length;
32};
33
34static void xioctl(int fh, int request, void *arg)
35{
36 int r;
37
38 do {
39 r = v4l2_ioctl(fh, request, arg);
40 } while (r == -1 && ((errno == EINTR) || (errno == EAGAIN)));
41
42 if (r == -1) {
43 fprintf(stderr, "error %d, %s\n", errno, strerror(errno));
44 exit(EXIT_FAILURE);
45 }
46}
47
48int main(int argc, char **argv)
49{
50 struct <link linkend="v4l2-format">v4l2_format</link> fmt;
51 struct <link linkend="v4l2-buffer">v4l2_buffer</link> buf;
52 struct <link linkend="v4l2-requestbuffers">v4l2_requestbuffers</link> req;
53 enum <link linkend="v4l2-buf-type">v4l2_buf_type</link> type;
54 fd_set fds;
55 struct timeval tv;
56 int r, fd = -1;
57 unsigned int i, n_buffers;
58 char *dev_name = "/dev/video0";
59 char out_name[256];
60 FILE *fout;
61 struct buffer *buffers;
62
63 fd = v4l2_open(dev_name, O_RDWR | O_NONBLOCK, 0);
64 if (fd < 0) {
65 perror("Cannot open device");
66 exit(EXIT_FAILURE);
67 }
68
69 CLEAR(fmt);
70 fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
71 fmt.fmt.pix.width = 640;
72 fmt.fmt.pix.height = 480;
73 fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB24;
74 fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
75 xioctl(fd, VIDIOC_S_FMT, &fmt);
76 if (fmt.fmt.pix.pixelformat != V4L2_PIX_FMT_RGB24) {
77 printf("Libv4l didn't accept RGB24 format. Can't proceed.\n");
78 exit(EXIT_FAILURE);
79 }
80 if ((fmt.fmt.pix.width != 640) || (fmt.fmt.pix.height != 480))
81 printf("Warning: driver is sending image at %dx%d\n",
82 fmt.fmt.pix.width, fmt.fmt.pix.height);
83
84 CLEAR(req);
85 req.count = 2;
86 req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
87 req.memory = V4L2_MEMORY_MMAP;
88 xioctl(fd, VIDIOC_REQBUFS, &req);
89
90 buffers = calloc(req.count, sizeof(*buffers));
91 for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {
92 CLEAR(buf);
93
94 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
95 buf.memory = V4L2_MEMORY_MMAP;
96 buf.index = n_buffers;
97
98 xioctl(fd, VIDIOC_QUERYBUF, &buf);
99
100 buffers[n_buffers].length = buf.length;
101 buffers[n_buffers].start = v4l2_mmap(NULL, buf.length,
102 PROT_READ | PROT_WRITE, MAP_SHARED,
103 fd, buf.m.offset);
104
105 if (MAP_FAILED == buffers[n_buffers].start) {
106 perror("mmap");
107 exit(EXIT_FAILURE);
108 }
109 }
110
111 for (i = 0; i < n_buffers; ++i) {
112 CLEAR(buf);
113 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
114 buf.memory = V4L2_MEMORY_MMAP;
115 buf.index = i;
116 xioctl(fd, VIDIOC_QBUF, &buf);
117 }
118 type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
119
120 xioctl(fd, VIDIOC_STREAMON, &type);
121 for (i = 0; i < 20; i++) {
122 do {
123 FD_ZERO(&fds);
124 FD_SET(fd, &fds);
125
126 /* Timeout. */
127 tv.tv_sec = 2;
128 tv.tv_usec = 0;
129
130 r = select(fd + 1, &fds, NULL, NULL, &tv);
131 } while ((r == -1 && (errno = EINTR)));
132 if (r == -1) {
133 perror("select");
134 return errno;
135 }
136
137 CLEAR(buf);
138 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
139 buf.memory = V4L2_MEMORY_MMAP;
140 xioctl(fd, VIDIOC_DQBUF, &buf);
141
142 sprintf(out_name, "out%03d.ppm", i);
143 fout = fopen(out_name, "w");
144 if (!fout) {
145 perror("Cannot open image");
146 exit(EXIT_FAILURE);
147 }
148 fprintf(fout, "P6\n%d %d 255\n",
149 fmt.fmt.pix.width, fmt.fmt.pix.height);
150 fwrite(buffers[buf.index].start, buf.bytesused, 1, fout);
151 fclose(fout);
152
153 xioctl(fd, VIDIOC_QBUF, &buf);
154 }
155
156 type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
157 xioctl(fd, VIDIOC_STREAMOFF, &type);
158 for (i = 0; i < n_buffers; ++i)
159 v4l2_munmap(buffers[i].start, buffers[i].length);
160 v4l2_close(fd);
161
162 return 0;
163}
164</programlisting>