libmpdemux/yuv4mpeg.c

   1 /*
   2  *  yuv4mpeg.c:  Functions for reading and writing "new" YUV4MPEG streams
   3  *
   4  *  Copyright (C) 2001 Matthew J. Marjanovic <maddog@mir.com>
   5  *
   6  *  This file is part of the MJPEG Tools package (mjpeg.sourceforge.net).
   7  *  Ported to mplayer by Rik Snel <rsnel@cube.dyndns.org>
   8  *
   9  *  This program is free software; you can redistribute it and/or
  10  *  modify it under the terms of the GNU General Public License
  11  *  as published by the Free Software Foundation; either version 2
  12  *  of the License, or (at your option) any later version.
  13  *
  14  *  This program is distributed in the hope that it will be useful,
  15  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  *  GNU General Public License for more details.
  18  *
  19  *  You should have received a copy of the GNU General Public License
  20  *  along with this program; if not, write to the Free Software
  21  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  *
  23  */
  24
  25 #include "config.h"
  26
  27 #include <unistd.h>
  28 #include <stdio.h>
  29 #include <stdlib.h>
  30 #include <string.h>
  31 #include "yuv4mpeg.h"
  32 #include "yuv4mpeg_intern.h"
  33 #include "mp_msg.h"
  34
  35 static int _y4mparam_allow_unknown_tags = 1;  /* default is forgiveness */
  36
  37 static void *(*_y4m_alloc)(size_t bytes) = malloc;
  38 static void (*_y4m_free)(void *ptr) = free;
  39
  40 int y4m_allow_unknown_tags(int yn) {
  41         int old = _y4mparam_allow_unknown_tags;
  42         if (yn >= 0) _y4mparam_allow_unknown_tags = (yn) ? 1 : 0;
  43         return old;
  44 }
  45
  46
  47
  48 /*************************************************************************
  49  *
  50  * Convenience functions for fd read/write
  51  *
  52  *   - guaranteed to transfer entire payload (or fail)
  53  *   - returns:
  54  *               0 on complete success
  55  *               +(# of remaining bytes) on eof (for y4m_read)
  56  *               -(# of rem. bytes) on error (and ERRNO should be set)
  57  *
  58  *************************************************************************/
  59
  60
  61 ssize_t y4m_read(stream_t *s, char *buf, size_t len)
  62 {
  63    ssize_t n;
  64
  65    while (len > 0) {
  66      n = stream_read(s, buf, len);
  67      if (n <= 0) {
  68        /* return amount left to read */
  69        if (n == 0)
  70          return len;  /* n == 0 --> eof */
  71        else
  72          return -len; /* n < 0 --> error */
  73      }
  74      buf += n;
  75      len -= n;
  76    }
  77    return 0;
  78 }
  79
  80
  81 #if 0 /* not needed */
  82 ssize_t y4m_write(int fd, char *buf, size_t len)
  83 {
  84    ssize_t n;
  85
  86    while (len > 0) {
  87      n = write(fd, buf, len);
  88      if (n < 0) return -len;  /* return amount left to write */
  89      buf += n;
  90      len -= n;
  91    }
  92    return 0;
  93 }
  94 #endif
  95
  96
  97 /*************************************************************************
  98  *
  99  * "Extra tags" handling
 100  *
 101  *************************************************************************/
 102
 103
 104 static char *y4m_new_xtag(void)
 105 {
 106   return _y4m_alloc(Y4M_MAX_XTAG_SIZE);
 107 }
 108
 109
 110 void y4m_init_xtag_list(y4m_xtag_list_t *xtags)
 111 {
 112   int i;
 113   xtags->count = 0;
 114   for (i = 0; i < Y4M_MAX_XTAGS; i++) {
 115     xtags->tags[i] = NULL;
 116   }
 117 }
 118
 119
 120 void y4m_fini_xtag_list(y4m_xtag_list_t *xtags)
 121 {
 122   int i;
 123   for (i = 0; i < Y4M_MAX_XTAGS; i++) {
 124     if (xtags->tags[i] != NULL) {
 125       _y4m_free(xtags->tags[i]);
 126       xtags->tags[i] = NULL;
 127     }
 128   }
 129   xtags->count = 0;
 130 }
 131
 132
 133 void y4m_copy_xtag_list(y4m_xtag_list_t *dest, const y4m_xtag_list_t *src)
 134 {
 135   int i;
 136   for (i = 0; i < src->count; i++) {
 137     if (dest->tags[i] == NULL)
 138       dest->tags[i] = y4m_new_xtag();
 139     strncpy(dest->tags[i], src->tags[i], Y4M_MAX_XTAG_SIZE);
 140   }
 141   dest->count = src->count;
 142 }
 143
 144
 145
 146 #if 0
 147 static int y4m_snprint_xtags(char *s, int maxn, y4m_xtag_list_t *xtags)
 148 {
 149   int i, room;
 150
 151   for (i = 0, room = maxn - 1; i < xtags->count; i++) {
 152     int n = snprintf(s, room + 1, " %s", xtags->tags[i]);
 153     if ((n < 0) || (n > room)) return Y4M_ERR_HEADER;
 154     s += n;
 155     room -= n;
 156   }
 157   s[0] = '\n';  /* finish off header with newline */
 158   s[1] = '\0';  /* ...and end-of-string           */
 159   return Y4M_OK;
 160 }
 161 #endif
 162
 163
 164 int y4m_xtag_count(const y4m_xtag_list_t *xtags)
 165 {
 166   return xtags->count;
 167 }
 168
 169
 170 const char *y4m_xtag_get(const y4m_xtag_list_t *xtags, int n)
 171 {
 172   if (n >= xtags->count)
 173     return NULL;
 174   else
 175     return xtags->tags[n];
 176 }
 177
 178
 179 int y4m_xtag_add(y4m_xtag_list_t *xtags, const char *tag)
 180 {
 181   if (xtags->count >= Y4M_MAX_XTAGS) return Y4M_ERR_XXTAGS;
 182   if (xtags->tags[xtags->count] == NULL) {
 183     xtags->tags[xtags->count] = y4m_new_xtag();
 184   }
 185   strncpy(xtags->tags[xtags->count], tag, Y4M_MAX_XTAG_SIZE);
 186   (xtags->count)++;
 187   return Y4M_OK;
 188 }
 189
 190
 191 int y4m_xtag_remove(y4m_xtag_list_t *xtags, int n)
 192 {
 193   int i;
 194   char *q;
 195
 196   if ((n < 0) || (n >= xtags->count)) return Y4M_ERR_RANGE;
 197   q = xtags->tags[n];
 198   for (i = n; i < (xtags->count - 1); i++)
 199     xtags->tags[i] = xtags->tags[i+1];
 200   xtags->tags[i] = q;
 201   (xtags->count)--;
 202   return Y4M_OK;
 203 }
 204
 205
 206 int y4m_xtag_clearlist(y4m_xtag_list_t *xtags)
 207 {
 208   xtags->count = 0;
 209   return Y4M_OK;
 210 }
 211
 212
 213 int y4m_xtag_addlist(y4m_xtag_list_t *dest, const y4m_xtag_list_t *src)
 214 {
 215   int i, j;
 216
 217   if ((dest->count + src->count) > Y4M_MAX_XTAGS) return Y4M_ERR_XXTAGS;
 218   for (i = dest->count, j = 0;
 219        j < src->count;
 220        i++, j++) {
 221     if (dest->tags[i] == NULL)
 222       dest->tags[i] = y4m_new_xtag();
 223     strncpy(dest->tags[i], src->tags[i], Y4M_MAX_XTAG_SIZE);
 224   }
 225   dest->count += src->count;
 226   return Y4M_OK;
 227 }
 228
 229
 230 /*************************************************************************
 231  *
 232  * Creators/destructors for y4m_*_info_t structures
 233  *
 234  *************************************************************************/
 235
 236
 237 void y4m_init_stream_info(y4m_stream_info_t *info)
 238 {
 239   if (info == NULL) return;
 240   /* initialize info */
 241   info->width = Y4M_UNKNOWN;
 242   info->height = Y4M_UNKNOWN;
 243   info->interlace = Y4M_UNKNOWN;
 244   info->framerate = y4m_fps_UNKNOWN;
 245   info->sampleaspect = y4m_sar_UNKNOWN;
 246   y4m_init_xtag_list(&(info->x_tags));
 247 }
 248
 249
 250 void y4m_copy_stream_info(y4m_stream_info_t *dest, y4m_stream_info_t *src)
 251 {
 252   if ((dest == NULL) || (src == NULL)) return;
 253   /* copy info */
 254   dest->width = src->width;
 255   dest->height = src->height;
 256   dest->interlace = src->interlace;
 257   dest->framerate = src->framerate;
 258   dest->sampleaspect = src->sampleaspect;
 259   y4m_copy_xtag_list(&(dest->x_tags), &(src->x_tags));
 260 }
 261
 262
 263 void y4m_fini_stream_info(y4m_stream_info_t *info)
 264 {
 265   if (info == NULL) return;
 266   y4m_fini_xtag_list(&(info->x_tags));
 267 }
 268
 269
 270 void y4m_si_set_width(y4m_stream_info_t *si, int width)
 271 {
 272   si->width = width;
 273   si->framelength = (si->height * si->width) * 3 / 2;
 274 }
 275
 276 int y4m_si_get_width(y4m_stream_info_t *si)
 277 { return si->width; }
 278
 279 void y4m_si_set_height(y4m_stream_info_t *si, int height)
 280 {
 281   si->height = height;
 282   si->framelength = (si->height * si->width) * 3 / 2;
 283 }
 284
 285 int y4m_si_get_height(y4m_stream_info_t *si)
 286 { return si->height; }
 287
 288 void y4m_si_set_interlace(y4m_stream_info_t *si, int interlace)
 289 { si->interlace = interlace; }
 290
 291 int y4m_si_get_interlace(y4m_stream_info_t *si)
 292 { return si->interlace; }
 293
 294 void y4m_si_set_framerate(y4m_stream_info_t *si, y4m_ratio_t framerate)
 295 { si->framerate = framerate; }
 296
 297 y4m_ratio_t y4m_si_get_framerate(y4m_stream_info_t *si)
 298 { return si->framerate; }
 299
 300 void y4m_si_set_sampleaspect(y4m_stream_info_t *si, y4m_ratio_t sar)
 301 { si->sampleaspect = sar; }
 302
 303 y4m_ratio_t y4m_si_get_sampleaspect(y4m_stream_info_t *si)
 304 { return si->sampleaspect; }
 305
 306 int y4m_si_get_framelength(y4m_stream_info_t *si)
 307 { return si->framelength; }
 308
 309 y4m_xtag_list_t *y4m_si_xtags(y4m_stream_info_t *si)
 310 { return &(si->x_tags); }
 311
 312
 313
 314 void y4m_init_frame_info(y4m_frame_info_t *info)
 315 {
 316   if (info == NULL) return;
 317   /* initialize info */
 318   y4m_init_xtag_list(&(info->x_tags));
 319 }
 320
 321
 322 void y4m_copy_frame_info(y4m_frame_info_t *dest, y4m_frame_info_t *src)
 323 {
 324   if ((dest == NULL) || (src == NULL)) return;
 325   /* copy info */
 326   y4m_copy_xtag_list(&(dest->x_tags), &(src->x_tags));
 327 }
 328
 329
 330 void y4m_fini_frame_info(y4m_frame_info_t *info)
 331 {
 332   if (info == NULL) return;
 333   y4m_fini_xtag_list(&(info->x_tags));
 334 }
 335
 336
 337
 338 /*************************************************************************
 339  *
 340  * Tag parsing
 341  *
 342  *************************************************************************/
 343
 344 int y4m_parse_stream_tags(char *s, y4m_stream_info_t *i)
 345 {
 346   char *token, *value;
 347   char tag;
 348   int err;
 349
 350   /* parse fields */
 351   for (token = strtok(s, Y4M_DELIM);
 352        token != NULL;
 353        token = strtok(NULL, Y4M_DELIM)) {
 354     if (token[0] == '\0') continue;   /* skip empty strings */
 355     tag = token[0];
 356     value = token + 1;
 357     switch (tag) {
 358     case 'W':  /* width */
 359       i->width = atoi(value);
 360       if (i->width <= 0) return Y4M_ERR_RANGE;
 361       break;
 362     case 'H':  /* height */
 363       i->height = atoi(value);
 364       if (i->height <= 0) return Y4M_ERR_RANGE;
 365       break;
 366     case 'F':  /* frame rate (fps) */
 367       if ((err = y4m_parse_ratio(&(i->framerate), value)) != Y4M_OK)
 368         return err;
 369       if (i->framerate.n < 0) return Y4M_ERR_RANGE;
 370       break;
 371     case 'I':  /* interlacing */
 372       switch (value[0]) {
 373       case 'p':  i->interlace = Y4M_ILACE_NONE; break;
 374       case 't':  i->interlace = Y4M_ILACE_TOP_FIRST; break;
 375       case 'b':  i->interlace = Y4M_ILACE_BOTTOM_FIRST; break;
 376       case '?':
 377       default:
 378         i->interlace = Y4M_UNKNOWN; break;
 379       }
 380       break;
 381     case 'A':  /* sample (pixel) aspect ratio */
 382       if ((err = y4m_parse_ratio(&(i->sampleaspect), value)) != Y4M_OK)
 383         return err;
 384       if (i->sampleaspect.n < 0) return Y4M_ERR_RANGE;
 385       break;
 386     case 'X':  /* 'X' meta-tag */
 387       if ((err = y4m_xtag_add(&(i->x_tags), token)) != Y4M_OK) return err;
 388       break;
 389     default:
 390       /* possible error on unknown options */
 391       if (_y4mparam_allow_unknown_tags) {
 392         /* unknown tags ok:  store in xtag list and warn... */
 393         if ((err = y4m_xtag_add(&(i->x_tags), token)) != Y4M_OK) return err;
 394         mp_msg(MSGT_DEMUX, MSGL_WARN, "Unknown stream tag encountered:  '%s'\n", token);
 395       } else {
 396         /* unknown tags are *not* ok */
 397         return Y4M_ERR_BADTAG;
 398       }
 399       break;
 400     }
 401   }
 402   /* Error checking... width and height must be known since we can't
 403    * parse without them
 404    */
 405   if( i->width == Y4M_UNKNOWN || i->height == Y4M_UNKNOWN )
 406           return Y4M_ERR_HEADER;
 407   /* ta da!  done. */
 408   return Y4M_OK;
 409 }
 410
 411
 412
 413 static int y4m_parse_frame_tags(char *s, y4m_frame_info_t *i)
 414 {
 415   char *token, *value;
 416   char tag;
 417   int err;
 418
 419   /* parse fields */
 420   for (token = strtok(s, Y4M_DELIM);
 421        token != NULL;
 422        token = strtok(NULL, Y4M_DELIM)) {
 423     if (token[0] == '\0') continue;   /* skip empty strings */
 424     tag = token[0];
 425     value = token + 1;
 426     switch (tag) {
 427     case 'X':  /* 'X' meta-tag */
 428       if ((err = y4m_xtag_add(&(i->x_tags), token)) != Y4M_OK) return err;
 429       break;
 430     default:
 431       /* possible error on unknown options */
 432       if (_y4mparam_allow_unknown_tags) {
 433         /* unknown tags ok:  store in xtag list and warn... */
 434         if ((err = y4m_xtag_add(&(i->x_tags), token)) != Y4M_OK) return err;
 435         mp_msg(MSGT_DEMUX, MSGL_WARN, "Unknown frame tag encountered:  '%s'\n", token);
 436       } else {
 437         /* unknown tags are *not* ok */
 438         return Y4M_ERR_BADTAG;
 439       }
 440       break;
 441     }
 442   }
 443   /* ta da!  done. */
 444   return Y4M_OK;
 445 }
 446
 447
 448
 449
 450
 451 /*************************************************************************
 452  *
 453  * Read/Write stream header
 454  *
 455  *************************************************************************/
 456
 457
 458 int y4m_read_stream_header(stream_t *s, y4m_stream_info_t *i)
 459 {
 460    char line[Y4M_LINE_MAX];
 461    char *p;
 462    int n;
 463    int err;
 464
 465    /* read the header line */
 466    for (n = 0, p = line; n < Y4M_LINE_MAX; n++, p++) {
 467      if (y4m_read(s, p, 1))
 468        return Y4M_ERR_SYSTEM;
 469      if (*p == '\n') {
 470        *p = '\0';           /* Replace linefeed by end of string */
 471        break;
 472      }
 473    }
 474    if (n >= Y4M_LINE_MAX)
 475       return Y4M_ERR_HEADER;
 476    /* look for keyword in header */
 477    if (strncmp(line, Y4M_MAGIC, strlen(Y4M_MAGIC)))
 478     return Y4M_ERR_MAGIC;
 479    if ((err = y4m_parse_stream_tags(line + strlen(Y4M_MAGIC), i)) != Y4M_OK)
 480      return err;
 481
 482    i->framelength = (i->height * i->width) * 3 / 2;
 483    return Y4M_OK;
 484 }
 485
 486
 487 #if 0
 488 int y4m_write_stream_header(int fd, y4m_stream_info_t *i)
 489 {
 490   char s[Y4M_LINE_MAX+1];
 491   int n;
 492   int err;
 493
 494   y4m_ratio_reduce(&(i->framerate));
 495   y4m_ratio_reduce(&(i->sampleaspect));
 496   n = snprintf(s, sizeof(s), "%s W%d H%d F%d:%d I%s A%d:%d",
 497                Y4M_MAGIC,
 498                i->width,
 499                i->height,
 500                i->framerate.n, i->framerate.d,
 501                (i->interlace == Y4M_ILACE_NONE) ? "p" :
 502                (i->interlace == Y4M_ILACE_TOP_FIRST) ? "t" :
 503                (i->interlace == Y4M_ILACE_BOTTOM_FIRST) ? "b" : "?",
 504                i->sampleaspect.n, i->sampleaspect.d);
 505   if ((n < 0) || (n > Y4M_LINE_MAX)) return Y4M_ERR_HEADER;
 506   if ((err = y4m_snprint_xtags(s + n, sizeof(s) - n - 1, &(i->x_tags)))
 507       != Y4M_OK)
 508     return err;
 509   /* non-zero on error */
 510   return (y4m_write(fd, s, strlen(s)) ? Y4M_ERR_SYSTEM : Y4M_OK);
 511 }
 512 #endif
 513
 514
 515
 516
 517 /*************************************************************************
 518  *
 519  * Read/Write frame header
 520  *
 521  *************************************************************************/
 522
 523 int y4m_read_frame_header(stream_t *s, y4m_frame_info_t *i)
 524 {
 525   char line[Y4M_LINE_MAX];
 526   char *p;
 527   int n;
 528   ssize_t remain;
 529
 530   /* This is more clever than read_stream_header...
 531      Try to read "FRAME\n" all at once, and don't try to parse
 532      if nothing else is there...
 533   */
 534   remain = y4m_read(s, line, sizeof(Y4M_FRAME_MAGIC));
 535   if (remain != 0)
 536   {
 537           /* A clean EOF should end exactly at a frame-boundary */
 538           if( remain == sizeof(Y4M_FRAME_MAGIC) )
 539                   return Y4M_ERR_EOF;
 540           else
 541                   return Y4M_ERR_SYSTEM;
 542   }
 543   if (strncmp(line, Y4M_FRAME_MAGIC, sizeof(Y4M_FRAME_MAGIC)-1))
 544     return Y4M_ERR_MAGIC;
 545   if (line[sizeof(Y4M_FRAME_MAGIC)-1] == '\n')
 546     return Y4M_OK; /* done -- no tags:  that was the end-of-line. */
 547
 548   if (line[sizeof(Y4M_FRAME_MAGIC)-1] != Y4M_DELIM[0]) {
 549     return Y4M_ERR_MAGIC; /* wasn't a space -- what was it? */
 550   }
 551
 552   /* proceed to get the tags... (overwrite the magic) */
 553   for (n = 0, p = line; n < Y4M_LINE_MAX; n++, p++) {
 554     if (y4m_read(s, p, 1))
 555       return Y4M_ERR_SYSTEM;
 556     if (*p == '\n') {
 557       *p = '\0';           /* Replace linefeed by end of string */
 558       break;
 559     }
 560   }
 561   if (n >= Y4M_LINE_MAX) return Y4M_ERR_HEADER;
 562   /* non-zero on error */
 563   return y4m_parse_frame_tags(line, i);
 564 }
 565
 566
 567 #if 0
 568 int y4m_write_frame_header(int fd, y4m_frame_info_t *i)
 569 {
 570   char s[Y4M_LINE_MAX+1];
 571   int n;
 572   int err;
 573
 574   n = snprintf(s, sizeof(s), "%s", Y4M_FRAME_MAGIC);
 575   if ((n < 0) || (n > Y4M_LINE_MAX)) return Y4M_ERR_HEADER;
 576   if ((err = y4m_snprint_xtags(s + n, sizeof(s) - n - 1, &(i->x_tags)))
 577       != Y4M_OK)
 578     return err;
 579   /* non-zero on error */
 580   return (y4m_write(fd, s, strlen(s)) ? Y4M_ERR_SYSTEM : Y4M_OK);
 581 }
 582 #endif
 583
 584
 585
 586 /*************************************************************************
 587  *
 588  * Read/Write entire frame
 589  *
 590  *************************************************************************/
 591
 592 int y4m_read_frame(stream_t *s, y4m_stream_info_t *si,
 593                    y4m_frame_info_t *fi, unsigned char *yuv[3])
 594 {
 595   int err;
 596   int w = si->width;
 597   int h = si->height;
 598
 599   /* Read frame header */
 600   if ((err = y4m_read_frame_header(s, fi)) != Y4M_OK) return err;
 601   /* Read luminance scanlines */
 602   if (y4m_read(s, yuv[0], w*h)) return Y4M_ERR_SYSTEM;
 603   /* Read chrominance scanlines */
 604   if (y4m_read(s, yuv[1], w*h/4)) return Y4M_ERR_SYSTEM;
 605   if (y4m_read(s, yuv[2], w*h/4)) return Y4M_ERR_SYSTEM;
 606
 607   return Y4M_OK;
 608 }
 609
 610
 611
 612 #if 0
 613 int y4m_write_frame(int fd, y4m_stream_info_t *si,
 614                     y4m_frame_info_t *fi, unsigned char *yuv[3])
 615 {
 616   int err;
 617   int w = si->width;
 618   int h = si->height;
 619
 620   /* Write frame header */
 621   if ((err = y4m_write_frame_header(fd, fi)) != Y4M_OK) return err;
 622   /* Write luminance,chrominance scanlines */
 623   if (y4m_write(fd, yuv[0], w*h) ||
 624       y4m_write(fd, yuv[1], w*h/4) ||
 625       y4m_write(fd, yuv[2], w*h/4))
 626     return Y4M_ERR_SYSTEM;
 627   return Y4M_OK;
 628 }
 629 #endif
 630
 631
 632 /*************************************************************************
 633  *
 634  * Read/Write entire frame, (de)interleaved (to)from two separate fields
 635  *
 636  *************************************************************************/
 637
 638 #if 0
 639 int y4m_read_fields(int fd, y4m_stream_info_t *si, y4m_frame_info_t *fi,
 640                     unsigned char *upper_field[3],
 641                     unsigned char *lower_field[3])
 642 {
 643   int i, y, err;
 644   int width = si->width;
 645   int height = si->height;
 646
 647   /* Read frame header */
 648   if ((err = y4m_read_frame_header(fd, fi)) != Y4M_OK) return err;
 649   /* Read Y', Cb, and Cr planes */
 650   for (i = 0; i < 3; i++) {
 651     unsigned char *srctop = upper_field[i];
 652     unsigned char *srcbot = lower_field[i];
 653     /* alternately write one line from each */
 654     for (y = 0; y < height; y += 2) {
 655       if (y4m_read(fd, srctop, width)) return Y4M_ERR_SYSTEM;
 656       srctop += width;
 657       if (y4m_read(fd, srcbot, width)) return Y4M_ERR_SYSTEM;
 658       srcbot += width;
 659     }
 660     /* for chroma, width/height are half as big */
 661     if (i == 0) {
 662       width /= 2;
 663       height /= 2;
 664     }
 665   }
 666   return Y4M_OK;
 667 }
 668
 669
 670
 671 int y4m_write_fields(int fd, y4m_stream_info_t *si, y4m_frame_info_t *fi,
 672                      unsigned char *upper_field[3],
 673                      unsigned char *lower_field[3])
 674 {
 675   int i, y, err;
 676   int width = si->width;
 677   int height = si->height;
 678
 679   /* Write frame header */
 680   if ((err = y4m_write_frame_header(fd, fi)) != Y4M_OK) return err;
 681   /* Write Y', Cb, and Cr planes */
 682   for (i = 0; i < 3; i++) {
 683     unsigned char *srctop = upper_field[i];
 684     unsigned char *srcbot = lower_field[i];
 685     /* alternately write one line from each */
 686     for (y = 0; y < height; y += 2) {
 687       if (y4m_write(fd, srctop, width)) return Y4M_ERR_SYSTEM;
 688       srctop += width;
 689       if (y4m_write(fd, srcbot, width)) return Y4M_ERR_SYSTEM;
 690       srcbot += width;
 691     }
 692     /* for chroma, width/height are half as big */
 693     if (i == 0) {
 694       width /= 2;
 695       height /= 2;
 696     }
 697   }
 698   return Y4M_OK;
 699 }
 700 #endif
 701
 702
 703 /*************************************************************************
 704  *
 705  * Handy logging of stream info
 706  *
 707  *************************************************************************/
 708
 709 void y4m_log_stream_info(const char *prefix, y4m_stream_info_t *i)
 710 {
 711   char s[256];
 712
 713   snprintf(s, sizeof(s), "  frame size:  ");
 714   if (i->width == Y4M_UNKNOWN)
 715     snprintf(s+strlen(s), sizeof(s)-strlen(s), "(?)x");
 716   else
 717     snprintf(s+strlen(s), sizeof(s)-strlen(s), "%dx", i->width);
 718   if (i->height == Y4M_UNKNOWN)
 719     snprintf(s+strlen(s), sizeof(s)-strlen(s), "(?) pixels ");
 720   else
 721     snprintf(s+strlen(s), sizeof(s)-strlen(s), "%d pixels ", i->height);
 722   if (i->framelength == Y4M_UNKNOWN)
 723     snprintf(s+strlen(s), sizeof(s)-strlen(s), "(? bytes)");
 724   else
 725     snprintf(s+strlen(s), sizeof(s)-strlen(s), "(%d bytes)", i->framelength);
 726   mp_msg(MSGT_DEMUX, MSGL_V, "%s%s\n", prefix, s);
 727   if ((i->framerate.n == 0) && (i->framerate.d == 0))
 728     mp_msg(MSGT_DEMUX, MSGL_V, "%s  frame rate:  ??? fps\n", prefix);
 729   else
 730     mp_msg(MSGT_DEMUX, MSGL_V, "%s  frame rate:  %d/%d fps (~%f)\n", prefix,
 731               i->framerate.n, i->framerate.d,
 732               (double) i->framerate.n / (double) i->framerate.d);
 733   mp_msg(MSGT_DEMUX, MSGL_V, "%s   interlace:  %s\n", prefix,
 734           (i->interlace == Y4M_ILACE_NONE) ? "none/progressive" :
 735           (i->interlace == Y4M_ILACE_TOP_FIRST) ? "top-field-first" :
 736           (i->interlace == Y4M_ILACE_BOTTOM_FIRST) ? "bottom-field-first" :
 737           "anyone's guess");
 738   if ((i->sampleaspect.n == 0) && (i->sampleaspect.d == 0))
 739     mp_msg(MSGT_DEMUX, MSGL_V, "%ssample aspect ratio:  ?:?\n", prefix);
 740   else
 741     mp_msg(MSGT_DEMUX, MSGL_V, "%ssample aspect ratio:  %d:%d\n", prefix,
 742               i->sampleaspect.n, i->sampleaspect.d);
 743 }
 744
 745
 746 /*************************************************************************
 747  *
 748  * Convert error code to string
 749  *
 750  *************************************************************************/
 751
 752 const char *y4m_strerr(int err)
 753 {
 754   switch (err) {
 755   case Y4M_OK:          return "no error";
 756   case Y4M_ERR_RANGE:   return "parameter out of range";
 757   case Y4M_ERR_SYSTEM:  return "stream ended unexpectedly (failed read/write)";
 758   case Y4M_ERR_HEADER:  return "bad stream or frame header";
 759   case Y4M_ERR_BADTAG:  return "unknown header tag";
 760   case Y4M_ERR_MAGIC:   return "bad header magic";
 761   case Y4M_ERR_XXTAGS:  return "too many xtags";
 762   case Y4M_ERR_EOF:     return "end-of-file";
 763   default:
 764     return "unknown error code";
 765   }
 766 }