Documentation/DocBook/v4l/capture.c.xml

   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
  31 enum io_method {
  32         IO_METHOD_READ,
  33         IO_METHOD_MMAP,
  34         IO_METHOD_USERPTR,
  35 };
  36
  37 struct buffer {
  38         void   *start;
  39         size_t  length;
  40 };
  41
  42 static char            *dev_name;
  43 static enum io_method   io = IO_METHOD_MMAP;
  44 static int              fd = -1;
  45 struct buffer          *buffers;
  46 static unsigned int     n_buffers;
  47 static int              out_buf;
  48 static int              force_format;
  49 static int              frame_count = 70;
  50
  51 static 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
  57 static 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
  68 static 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
  78 static 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
 170 static 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
 209 static 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
 227 static 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
 275 static 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
 299 static 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
 317 static 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
 375 static 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
 413 static 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
 525 static void close_device(void)
 526 {
 527         if (-1 == close(fd))
 528                 errno_exit("close");
 529
 530         fd = -1;
 531 }
 532
 533 static 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
 557 static 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
 575 static const char short_options[] = "d:hmruofc:";
 576
 577 static const struct option
 578 long_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
 590 int 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>