summaryrefslogtreecommitdiffstats
path: root/Documentation/userspace-api/media/v4l/v4l2grab.c.rst
blob: eaa0f95048e70db90d12b60276f65444fa14bfb4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
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;
    }