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-rw-r--r--Documentation/DocBook/v4l/capture.c.xml659
1 files changed, 659 insertions, 0 deletions
diff --git a/Documentation/DocBook/v4l/capture.c.xml b/Documentation/DocBook/v4l/capture.c.xml
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1<programlisting>
2/*
3 * V4L2 video capture example
4 *
5 * This program can be used and distributed without restrictions.
6 *
7 * This program is provided with the V4L2 API
8 * see http://linuxtv.org/docs.php for more information
9 */
10
11#include &lt;stdio.h&gt;
12#include &lt;stdlib.h&gt;
13#include &lt;string.h&gt;
14#include &lt;assert.h&gt;
15
16#include &lt;getopt.h&gt; /* getopt_long() */
17
18#include &lt;fcntl.h&gt; /* low-level i/o */
19#include &lt;unistd.h&gt;
20#include &lt;errno.h&gt;
21#include &lt;sys/stat.h&gt;
22#include &lt;sys/types.h&gt;
23#include &lt;sys/time.h&gt;
24#include &lt;sys/mman.h&gt;
25#include &lt;sys/ioctl.h&gt;
26
27#include &lt;linux/videodev2.h&gt;
28
29#define CLEAR(x) memset(&amp;(x), 0, sizeof(x))
30
31enum io_method {
32 IO_METHOD_READ,
33 IO_METHOD_MMAP,
34 IO_METHOD_USERPTR,
35};
36
37struct buffer {
38 void *start;
39 size_t length;
40};
41
42static char *dev_name;
43static enum io_method io = IO_METHOD_MMAP;
44static int fd = -1;
45struct buffer *buffers;
46static unsigned int n_buffers;
47static int out_buf;
48static int force_format;
49static int frame_count = 70;
50
51static void errno_exit(const char *s)
52{
53 fprintf(stderr, "%s error %d, %s\n", s, errno, strerror(errno));
54 exit(EXIT_FAILURE);
55}
56
57static int xioctl(int fh, int request, void *arg)
58{
59 int r;
60
61 do {
62 r = ioctl(fh, request, arg);
63 } while (-1 == r &amp;&amp; EINTR == errno);
64
65 return r;
66}
67
68static void process_image(const void *p, int size)
69{
70 if (out_buf)
71 fwrite(p, size, 1, stdout);
72
73 fflush(stderr);
74 fprintf(stderr, ".");
75 fflush(stdout);
76}
77
78static int read_frame(void)
79{
80 struct <link linkend="v4l2-buffer">v4l2_buffer</link> buf;
81 unsigned int i;
82
83 switch (io) {
84 case IO_METHOD_READ:
85 if (-1 == read(fd, buffers[0].start, buffers[0].length)) {
86 switch (errno) {
87 case EAGAIN:
88 return 0;
89
90 case EIO:
91 /* Could ignore EIO, see spec. */
92
93 /* fall through */
94
95 default:
96 errno_exit("read");
97 }
98 }
99
100 process_image(buffers[0].start, buffers[0].length);
101 break;
102
103 case IO_METHOD_MMAP:
104 CLEAR(buf);
105
106 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
107 buf.memory = V4L2_MEMORY_MMAP;
108
109 if (-1 == xioctl(fd, VIDIOC_DQBUF, &amp;buf)) {
110 switch (errno) {
111 case EAGAIN:
112 return 0;
113
114 case EIO:
115 /* Could ignore EIO, see spec. */
116
117 /* fall through */
118
119 default:
120 errno_exit("VIDIOC_DQBUF");
121 }
122 }
123
124 assert(buf.index &lt; n_buffers);
125
126 process_image(buffers[buf.index].start, buf.bytesused);
127
128 if (-1 == xioctl(fd, VIDIOC_QBUF, &amp;buf))
129 errno_exit("VIDIOC_QBUF");
130 break;
131
132 case IO_METHOD_USERPTR:
133 CLEAR(buf);
134
135 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
136 buf.memory = V4L2_MEMORY_USERPTR;
137
138 if (-1 == xioctl(fd, VIDIOC_DQBUF, &amp;buf)) {
139 switch (errno) {
140 case EAGAIN:
141 return 0;
142
143 case EIO:
144 /* Could ignore EIO, see spec. */
145
146 /* fall through */
147
148 default:
149 errno_exit("VIDIOC_DQBUF");
150 }
151 }
152
153 for (i = 0; i &lt; n_buffers; ++i)
154 if (buf.m.userptr == (unsigned long)buffers[i].start
155 &amp;&amp; buf.length == buffers[i].length)
156 break;
157
158 assert(i &lt; n_buffers);
159
160 process_image((void *)buf.m.userptr, buf.bytesused);
161
162 if (-1 == xioctl(fd, VIDIOC_QBUF, &amp;buf))
163 errno_exit("VIDIOC_QBUF");
164 break;
165 }
166
167 return 1;
168}
169
170static void mainloop(void)
171{
172 unsigned int count;
173
174 count = frame_count;
175
176 while (count-- &gt; 0) {
177 for (;;) {
178 fd_set fds;
179 struct timeval tv;
180 int r;
181
182 FD_ZERO(&amp;fds);
183 FD_SET(fd, &amp;fds);
184
185 /* Timeout. */
186 tv.tv_sec = 2;
187 tv.tv_usec = 0;
188
189 r = select(fd + 1, &amp;fds, NULL, NULL, &amp;tv);
190
191 if (-1 == r) {
192 if (EINTR == errno)
193 continue;
194 errno_exit("select");
195 }
196
197 if (0 == r) {
198 fprintf(stderr, "select timeout\n");
199 exit(EXIT_FAILURE);
200 }
201
202 if (read_frame())
203 break;
204 /* EAGAIN - continue select loop. */
205 }
206 }
207}
208
209static void stop_capturing(void)
210{
211 enum <link linkend="v4l2-buf-type">v4l2_buf_type</link> type;
212
213 switch (io) {
214 case IO_METHOD_READ:
215 /* Nothing to do. */
216 break;
217
218 case IO_METHOD_MMAP:
219 case IO_METHOD_USERPTR:
220 type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
221 if (-1 == xioctl(fd, VIDIOC_STREAMOFF, &amp;type))
222 errno_exit("VIDIOC_STREAMOFF");
223 break;
224 }
225}
226
227static void start_capturing(void)
228{
229 unsigned int i;
230 enum <link linkend="v4l2-buf-type">v4l2_buf_type</link> type;
231
232 switch (io) {
233 case IO_METHOD_READ:
234 /* Nothing to do. */
235 break;
236
237 case IO_METHOD_MMAP:
238 for (i = 0; i &lt; n_buffers; ++i) {
239 struct <link linkend="v4l2-buffer">v4l2_buffer</link> buf;
240
241 CLEAR(buf);
242 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
243 buf.memory = V4L2_MEMORY_MMAP;
244 buf.index = i;
245
246 if (-1 == xioctl(fd, VIDIOC_QBUF, &amp;buf))
247 errno_exit("VIDIOC_QBUF");
248 }
249 type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
250 if (-1 == xioctl(fd, VIDIOC_STREAMON, &amp;type))
251 errno_exit("VIDIOC_STREAMON");
252 break;
253
254 case IO_METHOD_USERPTR:
255 for (i = 0; i &lt; n_buffers; ++i) {
256 struct <link linkend="v4l2-buffer">v4l2_buffer</link> buf;
257
258 CLEAR(buf);
259 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
260 buf.memory = V4L2_MEMORY_USERPTR;
261 buf.index = i;
262 buf.m.userptr = (unsigned long)buffers[i].start;
263 buf.length = buffers[i].length;
264
265 if (-1 == xioctl(fd, VIDIOC_QBUF, &amp;buf))
266 errno_exit("VIDIOC_QBUF");
267 }
268 type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
269 if (-1 == xioctl(fd, VIDIOC_STREAMON, &amp;type))
270 errno_exit("VIDIOC_STREAMON");
271 break;
272 }
273}
274
275static void uninit_device(void)
276{
277 unsigned int i;
278
279 switch (io) {
280 case IO_METHOD_READ:
281 free(buffers[0].start);
282 break;
283
284 case IO_METHOD_MMAP:
285 for (i = 0; i &lt; n_buffers; ++i)
286 if (-1 == munmap(buffers[i].start, buffers[i].length))
287 errno_exit("munmap");
288 break;
289
290 case IO_METHOD_USERPTR:
291 for (i = 0; i &lt; n_buffers; ++i)
292 free(buffers[i].start);
293 break;
294 }
295
296 free(buffers);
297}
298
299static void init_read(unsigned int buffer_size)
300{
301 buffers = calloc(1, sizeof(*buffers));
302
303 if (!buffers) {
304 fprintf(stderr, "Out of memory\n");
305 exit(EXIT_FAILURE);
306 }
307
308 buffers[0].length = buffer_size;
309 buffers[0].start = malloc(buffer_size);
310
311 if (!buffers[0].start) {
312 fprintf(stderr, "Out of memory\n");
313 exit(EXIT_FAILURE);
314 }
315}
316
317static void init_mmap(void)
318{
319 struct <link linkend="v4l2-requestbuffers">v4l2_requestbuffers</link> req;
320
321 CLEAR(req);
322
323 req.count = 4;
324 req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
325 req.memory = V4L2_MEMORY_MMAP;
326
327 if (-1 == xioctl(fd, VIDIOC_REQBUFS, &amp;req)) {
328 if (EINVAL == errno) {
329 fprintf(stderr, "%s does not support "
330 "memory mapping\n", dev_name);
331 exit(EXIT_FAILURE);
332 } else {
333 errno_exit("VIDIOC_REQBUFS");
334 }
335 }
336
337 if (req.count &lt; 2) {
338 fprintf(stderr, "Insufficient buffer memory on %s\n",
339 dev_name);
340 exit(EXIT_FAILURE);
341 }
342
343 buffers = calloc(req.count, sizeof(*buffers));
344
345 if (!buffers) {
346 fprintf(stderr, "Out of memory\n");
347 exit(EXIT_FAILURE);
348 }
349
350 for (n_buffers = 0; n_buffers &lt; req.count; ++n_buffers) {
351 struct <link linkend="v4l2-buffer">v4l2_buffer</link> buf;
352
353 CLEAR(buf);
354
355 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
356 buf.memory = V4L2_MEMORY_MMAP;
357 buf.index = n_buffers;
358
359 if (-1 == xioctl(fd, VIDIOC_QUERYBUF, &amp;buf))
360 errno_exit("VIDIOC_QUERYBUF");
361
362 buffers[n_buffers].length = buf.length;
363 buffers[n_buffers].start =
364 mmap(NULL /* start anywhere */,
365 buf.length,
366 PROT_READ | PROT_WRITE /* required */,
367 MAP_SHARED /* recommended */,
368 fd, buf.m.offset);
369
370 if (MAP_FAILED == buffers[n_buffers].start)
371 errno_exit("mmap");
372 }
373}
374
375static void init_userp(unsigned int buffer_size)
376{
377 struct <link linkend="v4l2-requestbuffers">v4l2_requestbuffers</link> req;
378
379 CLEAR(req);
380
381 req.count = 4;
382 req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
383 req.memory = V4L2_MEMORY_USERPTR;
384
385 if (-1 == xioctl(fd, VIDIOC_REQBUFS, &amp;req)) {
386 if (EINVAL == errno) {
387 fprintf(stderr, "%s does not support "
388 "user pointer i/o\n", dev_name);
389 exit(EXIT_FAILURE);
390 } else {
391 errno_exit("VIDIOC_REQBUFS");
392 }
393 }
394
395 buffers = calloc(4, sizeof(*buffers));
396
397 if (!buffers) {
398 fprintf(stderr, "Out of memory\n");
399 exit(EXIT_FAILURE);
400 }
401
402 for (n_buffers = 0; n_buffers &lt; 4; ++n_buffers) {
403 buffers[n_buffers].length = buffer_size;
404 buffers[n_buffers].start = malloc(buffer_size);
405
406 if (!buffers[n_buffers].start) {
407 fprintf(stderr, "Out of memory\n");
408 exit(EXIT_FAILURE);
409 }
410 }
411}
412
413static void init_device(void)
414{
415 struct <link linkend="v4l2-capability">v4l2_capability</link> cap;
416 struct <link linkend="v4l2-cropcap">v4l2_cropcap</link> cropcap;
417 struct <link linkend="v4l2-crop">v4l2_crop</link> crop;
418 struct <link linkend="v4l2-format">v4l2_format</link> fmt;
419 unsigned int min;
420
421 if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &amp;cap)) {
422 if (EINVAL == errno) {
423 fprintf(stderr, "%s is no V4L2 device\n",
424 dev_name);
425 exit(EXIT_FAILURE);
426 } else {
427 errno_exit("VIDIOC_QUERYCAP");
428 }
429 }
430
431 if (!(cap.capabilities &amp; V4L2_CAP_VIDEO_CAPTURE)) {
432 fprintf(stderr, "%s is no video capture device\n",
433 dev_name);
434 exit(EXIT_FAILURE);
435 }
436
437 switch (io) {
438 case IO_METHOD_READ:
439 if (!(cap.capabilities &amp; V4L2_CAP_READWRITE)) {
440 fprintf(stderr, "%s does not support read i/o\n",
441 dev_name);
442 exit(EXIT_FAILURE);
443 }
444 break;
445
446 case IO_METHOD_MMAP:
447 case IO_METHOD_USERPTR:
448 if (!(cap.capabilities &amp; V4L2_CAP_STREAMING)) {
449 fprintf(stderr, "%s does not support streaming i/o\n",
450 dev_name);
451 exit(EXIT_FAILURE);
452 }
453 break;
454 }
455
456
457 /* Select video input, video standard and tune here. */
458
459
460 CLEAR(cropcap);
461
462 cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
463
464 if (0 == xioctl(fd, VIDIOC_CROPCAP, &amp;cropcap)) {
465 crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
466 crop.c = cropcap.defrect; /* reset to default */
467
468 if (-1 == xioctl(fd, VIDIOC_S_CROP, &amp;crop)) {
469 switch (errno) {
470 case EINVAL:
471 /* Cropping not supported. */
472 break;
473 default:
474 /* Errors ignored. */
475 break;
476 }
477 }
478 } else {
479 /* Errors ignored. */
480 }
481
482
483 CLEAR(fmt);
484
485 fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
486 if (force_format) {
487 fmt.fmt.pix.width = 640;
488 fmt.fmt.pix.height = 480;
489 fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
490 fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
491
492 if (-1 == xioctl(fd, VIDIOC_S_FMT, &amp;fmt))
493 errno_exit("VIDIOC_S_FMT");
494
495 /* Note VIDIOC_S_FMT may change width and height. */
496 } else {
497 /* Preserve original settings as set by v4l2-ctl for example */
498 if (-1 == xioctl(fd, VIDIOC_G_FMT, &amp;fmt))
499 errno_exit("VIDIOC_G_FMT");
500 }
501
502 /* Buggy driver paranoia. */
503 min = fmt.fmt.pix.width * 2;
504 if (fmt.fmt.pix.bytesperline &lt; min)
505 fmt.fmt.pix.bytesperline = min;
506 min = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height;
507 if (fmt.fmt.pix.sizeimage &lt; min)
508 fmt.fmt.pix.sizeimage = min;
509
510 switch (io) {
511 case IO_METHOD_READ:
512 init_read(fmt.fmt.pix.sizeimage);
513 break;
514
515 case IO_METHOD_MMAP:
516 init_mmap();
517 break;
518
519 case IO_METHOD_USERPTR:
520 init_userp(fmt.fmt.pix.sizeimage);
521 break;
522 }
523}
524
525static void close_device(void)
526{
527 if (-1 == close(fd))
528 errno_exit("close");
529
530 fd = -1;
531}
532
533static void open_device(void)
534{
535 struct stat st;
536
537 if (-1 == stat(dev_name, &amp;st)) {
538 fprintf(stderr, "Cannot identify '%s': %d, %s\n",
539 dev_name, errno, strerror(errno));
540 exit(EXIT_FAILURE);
541 }
542
543 if (!S_ISCHR(st.st_mode)) {
544 fprintf(stderr, "%s is no device\n", dev_name);
545 exit(EXIT_FAILURE);
546 }
547
548 fd = open(dev_name, O_RDWR /* required */ | O_NONBLOCK, 0);
549
550 if (-1 == fd) {
551 fprintf(stderr, "Cannot open '%s': %d, %s\n",
552 dev_name, errno, strerror(errno));
553 exit(EXIT_FAILURE);
554 }
555}
556
557static void usage(FILE *fp, int argc, char **argv)
558{
559 fprintf(fp,
560 "Usage: %s [options]\n\n"
561 "Version 1.3\n"
562 "Options:\n"
563 "-d | --device name Video device name [%s]\n"
564 "-h | --help Print this message\n"
565 "-m | --mmap Use memory mapped buffers [default]\n"
566 "-r | --read Use read() calls\n"
567 "-u | --userp Use application allocated buffers\n"
568 "-o | --output Outputs stream to stdout\n"
569 "-f | --format Force format to 640x480 YUYV\n"
570 "-c | --count Number of frames to grab [%i]\n"
571 "",
572 argv[0], dev_name, frame_count);
573}
574
575static const char short_options[] = "d:hmruofc:";
576
577static const struct option
578long_options[] = {
579 { "device", required_argument, NULL, 'd' },
580 { "help", no_argument, NULL, 'h' },
581 { "mmap", no_argument, NULL, 'm' },
582 { "read", no_argument, NULL, 'r' },
583 { "userp", no_argument, NULL, 'u' },
584 { "output", no_argument, NULL, 'o' },
585 { "format", no_argument, NULL, 'f' },
586 { "count", required_argument, NULL, 'c' },
587 { 0, 0, 0, 0 }
588};
589
590int main(int argc, char **argv)
591{
592 dev_name = "/dev/video0";
593
594 for (;;) {
595 int idx;
596 int c;
597
598 c = getopt_long(argc, argv,
599 short_options, long_options, &amp;idx);
600
601 if (-1 == c)
602 break;
603
604 switch (c) {
605 case 0: /* getopt_long() flag */
606 break;
607
608 case 'd':
609 dev_name = optarg;
610 break;
611
612 case 'h':
613 usage(stdout, argc, argv);
614 exit(EXIT_SUCCESS);
615
616 case 'm':
617 io = IO_METHOD_MMAP;
618 break;
619
620 case 'r':
621 io = IO_METHOD_READ;
622 break;
623
624 case 'u':
625 io = IO_METHOD_USERPTR;
626 break;
627
628 case 'o':
629 out_buf++;
630 break;
631
632 case 'f':
633 force_format++;
634 break;
635
636 case 'c':
637 errno = 0;
638 frame_count = strtol(optarg, NULL, 0);
639 if (errno)
640 errno_exit(optarg);
641 break;
642
643 default:
644 usage(stderr, argc, argv);
645 exit(EXIT_FAILURE);
646 }
647 }
648
649 open_device();
650 init_device();
651 start_capturing();
652 mainloop();
653 stop_capturing();
654 uninit_device();
655 close_device();
656 fprintf(stderr, "\n");
657 return 0;
658}
659</programlisting>
generated by cgit v1.2.2 (git 2.25.0) at 2024-12-12 22:57:21 -0500