1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2.. c:namespace:: V4L 3 4file: media/v4l/capture.c 5========================= 6 7.. code-block:: c 8 9 /* 10 * V4L2 video capture example 11 * 12 * This program can be used and distributed without restrictions. 13 * 14 * This program is provided with the V4L2 API 15 * see https://linuxtv.org/docs.php for more information 16 */ 17 18 #include <stdio.h> 19 #include <stdlib.h> 20 #include <string.h> 21 #include <assert.h> 22 23 #include <getopt.h> /* getopt_long() */ 24 25 #include <fcntl.h> /* low-level i/o */ 26 #include <unistd.h> 27 #include <errno.h> 28 #include <sys/stat.h> 29 #include <sys/types.h> 30 #include <sys/time.h> 31 #include <sys/mman.h> 32 #include <sys/ioctl.h> 33 34 #include <linux/videodev2.h> 35 36 #define CLEAR(x) memset(&(x), 0, sizeof(x)) 37 38 enum io_method { 39 IO_METHOD_READ, 40 IO_METHOD_MMAP, 41 IO_METHOD_USERPTR, 42 }; 43 44 struct buffer { 45 void *start; 46 size_t length; 47 }; 48 49 static char *dev_name; 50 static enum io_method io = IO_METHOD_MMAP; 51 static int fd = -1; 52 struct buffer *buffers; 53 static unsigned int n_buffers; 54 static int out_buf; 55 static int force_format; 56 static int frame_count = 70; 57 58 static void errno_exit(const char *s) 59 { 60 fprintf(stderr, "%s error %d, %s\n", s, errno, strerror(errno)); 61 exit(EXIT_FAILURE); 62 } 63 64 static int xioctl(int fh, int request, void *arg) 65 { 66 int r; 67 68 do { 69 r = ioctl(fh, request, arg); 70 } while (-1 == r && EINTR == errno); 71 72 return r; 73 } 74 75 static void process_image(const void *p, int size) 76 { 77 if (out_buf) 78 fwrite(p, size, 1, stdout); 79 80 fflush(stderr); 81 fprintf(stderr, "."); 82 fflush(stdout); 83 } 84 85 static int read_frame(void) 86 { 87 struct v4l2_buffer buf; 88 unsigned int i; 89 90 switch (io) { 91 case IO_METHOD_READ: 92 if (-1 == read(fd, buffers[0].start, buffers[0].length)) { 93 switch (errno) { 94 case EAGAIN: 95 return 0; 96 97 case EIO: 98 /* Could ignore EIO, see spec. */ 99 100 /* fall through */ 101 102 default: 103 errno_exit("read"); 104 } 105 } 106 107 process_image(buffers[0].start, buffers[0].length); 108 break; 109 110 case IO_METHOD_MMAP: 111 CLEAR(buf); 112 113 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; 114 buf.memory = V4L2_MEMORY_MMAP; 115 116 if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf)) { 117 switch (errno) { 118 case EAGAIN: 119 return 0; 120 121 case EIO: 122 /* Could ignore EIO, see spec. */ 123 124 /* fall through */ 125 126 default: 127 errno_exit("VIDIOC_DQBUF"); 128 } 129 } 130 131 assert(buf.index < n_buffers); 132 133 process_image(buffers[buf.index].start, buf.bytesused); 134 135 if (-1 == xioctl(fd, VIDIOC_QBUF, &buf)) 136 errno_exit("VIDIOC_QBUF"); 137 break; 138 139 case IO_METHOD_USERPTR: 140 CLEAR(buf); 141 142 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; 143 buf.memory = V4L2_MEMORY_USERPTR; 144 145 if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf)) { 146 switch (errno) { 147 case EAGAIN: 148 return 0; 149 150 case EIO: 151 /* Could ignore EIO, see spec. */ 152 153 /* fall through */ 154 155 default: 156 errno_exit("VIDIOC_DQBUF"); 157 } 158 } 159 160 for (i = 0; i < n_buffers; ++i) 161 if (buf.m.userptr == (unsigned long)buffers[i].start 162 && buf.length == buffers[i].length) 163 break; 164 165 assert(i < n_buffers); 166 167 process_image((void *)buf.m.userptr, buf.bytesused); 168 169 if (-1 == xioctl(fd, VIDIOC_QBUF, &buf)) 170 errno_exit("VIDIOC_QBUF"); 171 break; 172 } 173 174 return 1; 175 } 176 177 static void mainloop(void) 178 { 179 unsigned int count; 180 181 count = frame_count; 182 183 while (count-- > 0) { 184 for (;;) { 185 fd_set fds; 186 struct timeval tv; 187 int r; 188 189 FD_ZERO(&fds); 190 FD_SET(fd, &fds); 191 192 /* Timeout. */ 193 tv.tv_sec = 2; 194 tv.tv_usec = 0; 195 196 r = select(fd + 1, &fds, NULL, NULL, &tv); 197 198 if (-1 == r) { 199 if (EINTR == errno) 200 continue; 201 errno_exit("select"); 202 } 203 204 if (0 == r) { 205 fprintf(stderr, "select timeout\n"); 206 exit(EXIT_FAILURE); 207 } 208 209 if (read_frame()) 210 break; 211 /* EAGAIN - continue select loop. */ 212 } 213 } 214 } 215 216 static void stop_capturing(void) 217 { 218 enum v4l2_buf_type type; 219 220 switch (io) { 221 case IO_METHOD_READ: 222 /* Nothing to do. */ 223 break; 224 225 case IO_METHOD_MMAP: 226 case IO_METHOD_USERPTR: 227 type = V4L2_BUF_TYPE_VIDEO_CAPTURE; 228 if (-1 == xioctl(fd, VIDIOC_STREAMOFF, &type)) 229 errno_exit("VIDIOC_STREAMOFF"); 230 break; 231 } 232 } 233 234 static void start_capturing(void) 235 { 236 unsigned int i; 237 enum v4l2_buf_type type; 238 239 switch (io) { 240 case IO_METHOD_READ: 241 /* Nothing to do. */ 242 break; 243 244 case IO_METHOD_MMAP: 245 for (i = 0; i < n_buffers; ++i) { 246 struct v4l2_buffer buf; 247 248 CLEAR(buf); 249 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; 250 buf.memory = V4L2_MEMORY_MMAP; 251 buf.index = i; 252 253 if (-1 == xioctl(fd, VIDIOC_QBUF, &buf)) 254 errno_exit("VIDIOC_QBUF"); 255 } 256 type = V4L2_BUF_TYPE_VIDEO_CAPTURE; 257 if (-1 == xioctl(fd, VIDIOC_STREAMON, &type)) 258 errno_exit("VIDIOC_STREAMON"); 259 break; 260 261 case IO_METHOD_USERPTR: 262 for (i = 0; i < n_buffers; ++i) { 263 struct v4l2_buffer buf; 264 265 CLEAR(buf); 266 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; 267 buf.memory = V4L2_MEMORY_USERPTR; 268 buf.index = i; 269 buf.m.userptr = (unsigned long)buffers[i].start; 270 buf.length = buffers[i].length; 271 272 if (-1 == xioctl(fd, VIDIOC_QBUF, &buf)) 273 errno_exit("VIDIOC_QBUF"); 274 } 275 type = V4L2_BUF_TYPE_VIDEO_CAPTURE; 276 if (-1 == xioctl(fd, VIDIOC_STREAMON, &type)) 277 errno_exit("VIDIOC_STREAMON"); 278 break; 279 } 280 } 281 282 static void uninit_device(void) 283 { 284 unsigned int i; 285 286 switch (io) { 287 case IO_METHOD_READ: 288 free(buffers[0].start); 289 break; 290 291 case IO_METHOD_MMAP: 292 for (i = 0; i < n_buffers; ++i) 293 if (-1 == munmap(buffers[i].start, buffers[i].length)) 294 errno_exit("munmap"); 295 break; 296 297 case IO_METHOD_USERPTR: 298 for (i = 0; i < n_buffers; ++i) 299 free(buffers[i].start); 300 break; 301 } 302 303 free(buffers); 304 } 305 306 static void init_read(unsigned int buffer_size) 307 { 308 buffers = calloc(1, sizeof(*buffers)); 309 310 if (!buffers) { 311 fprintf(stderr, "Out of memory\n"); 312 exit(EXIT_FAILURE); 313 } 314 315 buffers[0].length = buffer_size; 316 buffers[0].start = malloc(buffer_size); 317 318 if (!buffers[0].start) { 319 fprintf(stderr, "Out of memory\n"); 320 exit(EXIT_FAILURE); 321 } 322 } 323 324 static void init_mmap(void) 325 { 326 struct v4l2_requestbuffers req; 327 328 CLEAR(req); 329 330 req.count = 4; 331 req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; 332 req.memory = V4L2_MEMORY_MMAP; 333 334 if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) { 335 if (EINVAL == errno) { 336 fprintf(stderr, "%s does not support " 337 "memory mapping\n", dev_name); 338 exit(EXIT_FAILURE); 339 } else { 340 errno_exit("VIDIOC_REQBUFS"); 341 } 342 } 343 344 if (req.count < 2) { 345 fprintf(stderr, "Insufficient buffer memory on %s\n", 346 dev_name); 347 exit(EXIT_FAILURE); 348 } 349 350 buffers = calloc(req.count, sizeof(*buffers)); 351 352 if (!buffers) { 353 fprintf(stderr, "Out of memory\n"); 354 exit(EXIT_FAILURE); 355 } 356 357 for (n_buffers = 0; n_buffers < req.count; ++n_buffers) { 358 struct v4l2_buffer buf; 359 360 CLEAR(buf); 361 362 buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; 363 buf.memory = V4L2_MEMORY_MMAP; 364 buf.index = n_buffers; 365 366 if (-1 == xioctl(fd, VIDIOC_QUERYBUF, &buf)) 367 errno_exit("VIDIOC_QUERYBUF"); 368 369 buffers[n_buffers].length = buf.length; 370 buffers[n_buffers].start = 371 mmap(NULL /* start anywhere */, 372 buf.length, 373 PROT_READ | PROT_WRITE /* required */, 374 MAP_SHARED /* recommended */, 375 fd, buf.m.offset); 376 377 if (MAP_FAILED == buffers[n_buffers].start) 378 errno_exit("mmap"); 379 } 380 } 381 382 static void init_userp(unsigned int buffer_size) 383 { 384 struct v4l2_requestbuffers req; 385 386 CLEAR(req); 387 388 req.count = 4; 389 req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; 390 req.memory = V4L2_MEMORY_USERPTR; 391 392 if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) { 393 if (EINVAL == errno) { 394 fprintf(stderr, "%s does not support " 395 "user pointer i/o\n", dev_name); 396 exit(EXIT_FAILURE); 397 } else { 398 errno_exit("VIDIOC_REQBUFS"); 399 } 400 } 401 402 buffers = calloc(4, sizeof(*buffers)); 403 404 if (!buffers) { 405 fprintf(stderr, "Out of memory\n"); 406 exit(EXIT_FAILURE); 407 } 408 409 for (n_buffers = 0; n_buffers < 4; ++n_buffers) { 410 buffers[n_buffers].length = buffer_size; 411 buffers[n_buffers].start = malloc(buffer_size); 412 413 if (!buffers[n_buffers].start) { 414 fprintf(stderr, "Out of memory\n"); 415 exit(EXIT_FAILURE); 416 } 417 } 418 } 419 420 static void init_device(void) 421 { 422 struct v4l2_capability cap; 423 struct v4l2_cropcap cropcap; 424 struct v4l2_crop crop; 425 struct v4l2_format fmt; 426 unsigned int min; 427 428 if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &cap)) { 429 if (EINVAL == errno) { 430 fprintf(stderr, "%s is no V4L2 device\n", 431 dev_name); 432 exit(EXIT_FAILURE); 433 } else { 434 errno_exit("VIDIOC_QUERYCAP"); 435 } 436 } 437 438 if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) { 439 fprintf(stderr, "%s is no video capture device\n", 440 dev_name); 441 exit(EXIT_FAILURE); 442 } 443 444 switch (io) { 445 case IO_METHOD_READ: 446 if (!(cap.capabilities & V4L2_CAP_READWRITE)) { 447 fprintf(stderr, "%s does not support read i/o\n", 448 dev_name); 449 exit(EXIT_FAILURE); 450 } 451 break; 452 453 case IO_METHOD_MMAP: 454 case IO_METHOD_USERPTR: 455 if (!(cap.capabilities & V4L2_CAP_STREAMING)) { 456 fprintf(stderr, "%s does not support streaming i/o\n", 457 dev_name); 458 exit(EXIT_FAILURE); 459 } 460 break; 461 } 462 463 464 /* Select video input, video standard and tune here. */ 465 466 467 CLEAR(cropcap); 468 469 cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; 470 471 if (0 == xioctl(fd, VIDIOC_CROPCAP, &cropcap)) { 472 crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; 473 crop.c = cropcap.defrect; /* reset to default */ 474 475 if (-1 == xioctl(fd, VIDIOC_S_CROP, &crop)) { 476 switch (errno) { 477 case EINVAL: 478 /* Cropping not supported. */ 479 break; 480 default: 481 /* Errors ignored. */ 482 break; 483 } 484 } 485 } else { 486 /* Errors ignored. */ 487 } 488 489 490 CLEAR(fmt); 491 492 fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; 493 if (force_format) { 494 fmt.fmt.pix.width = 640; 495 fmt.fmt.pix.height = 480; 496 fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV; 497 fmt.fmt.pix.field = V4L2_FIELD_INTERLACED; 498 499 if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt)) 500 errno_exit("VIDIOC_S_FMT"); 501 502 /* Note VIDIOC_S_FMT may change width and height. */ 503 } else { 504 /* Preserve original settings as set by v4l2-ctl for example */ 505 if (-1 == xioctl(fd, VIDIOC_G_FMT, &fmt)) 506 errno_exit("VIDIOC_G_FMT"); 507 } 508 509 /* Buggy driver paranoia. */ 510 min = fmt.fmt.pix.width * 2; 511 if (fmt.fmt.pix.bytesperline < min) 512 fmt.fmt.pix.bytesperline = min; 513 min = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height; 514 if (fmt.fmt.pix.sizeimage < min) 515 fmt.fmt.pix.sizeimage = min; 516 517 switch (io) { 518 case IO_METHOD_READ: 519 init_read(fmt.fmt.pix.sizeimage); 520 break; 521 522 case IO_METHOD_MMAP: 523 init_mmap(); 524 break; 525 526 case IO_METHOD_USERPTR: 527 init_userp(fmt.fmt.pix.sizeimage); 528 break; 529 } 530 } 531 532 static void close_device(void) 533 { 534 if (-1 == close(fd)) 535 errno_exit("close"); 536 537 fd = -1; 538 } 539 540 static void open_device(void) 541 { 542 struct stat st; 543 544 if (-1 == stat(dev_name, &st)) { 545 fprintf(stderr, "Cannot identify '%s': %d, %s\n", 546 dev_name, errno, strerror(errno)); 547 exit(EXIT_FAILURE); 548 } 549 550 if (!S_ISCHR(st.st_mode)) { 551 fprintf(stderr, "%s is no device\n", dev_name); 552 exit(EXIT_FAILURE); 553 } 554 555 fd = open(dev_name, O_RDWR /* required */ | O_NONBLOCK, 0); 556 557 if (-1 == fd) { 558 fprintf(stderr, "Cannot open '%s': %d, %s\n", 559 dev_name, errno, strerror(errno)); 560 exit(EXIT_FAILURE); 561 } 562 } 563 564 static void usage(FILE *fp, int argc, char **argv) 565 { 566 fprintf(fp, 567 "Usage: %s [options]\n\n" 568 "Version 1.3\n" 569 "Options:\n" 570 "-d | --device name Video device name [%s]\n" 571 "-h | --help Print this message\n" 572 "-m | --mmap Use memory mapped buffers [default]\n" 573 "-r | --read Use read() calls\n" 574 "-u | --userp Use application allocated buffers\n" 575 "-o | --output Outputs stream to stdout\n" 576 "-f | --format Force format to 640x480 YUYV\n" 577 "-c | --count Number of frames to grab [%i]\n" 578 "", 579 argv[0], dev_name, frame_count); 580 } 581 582 static const char short_options[] = "d:hmruofc:"; 583 584 static const struct option 585 long_options[] = { 586 { "device", required_argument, NULL, 'd' }, 587 { "help", no_argument, NULL, 'h' }, 588 { "mmap", no_argument, NULL, 'm' }, 589 { "read", no_argument, NULL, 'r' }, 590 { "userp", no_argument, NULL, 'u' }, 591 { "output", no_argument, NULL, 'o' }, 592 { "format", no_argument, NULL, 'f' }, 593 { "count", required_argument, NULL, 'c' }, 594 { 0, 0, 0, 0 } 595 }; 596 597 int main(int argc, char **argv) 598 { 599 dev_name = "/dev/video0"; 600 601 for (;;) { 602 int idx; 603 int c; 604 605 c = getopt_long(argc, argv, 606 short_options, long_options, &idx); 607 608 if (-1 == c) 609 break; 610 611 switch (c) { 612 case 0: /* getopt_long() flag */ 613 break; 614 615 case 'd': 616 dev_name = optarg; 617 break; 618 619 case 'h': 620 usage(stdout, argc, argv); 621 exit(EXIT_SUCCESS); 622 623 case 'm': 624 io = IO_METHOD_MMAP; 625 break; 626 627 case 'r': 628 io = IO_METHOD_READ; 629 break; 630 631 case 'u': 632 io = IO_METHOD_USERPTR; 633 break; 634 635 case 'o': 636 out_buf++; 637 break; 638 639 case 'f': 640 force_format++; 641 break; 642 643 case 'c': 644 errno = 0; 645 frame_count = strtol(optarg, NULL, 0); 646 if (errno) 647 errno_exit(optarg); 648 break; 649 650 default: 651 usage(stderr, argc, argv); 652 exit(EXIT_FAILURE); 653 } 654 } 655 656 open_device(); 657 init_device(); 658 start_capturing(); 659 mainloop(); 660 stop_capturing(); 661 uninit_device(); 662 close_device(); 663 fprintf(stderr, "\n"); 664 return 0; 665 } 666