libavformat/avidec.c

   1 /*
   2  * AVI decoder.
   3  * Copyright (c) 2001 Fabrice Bellard.
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the License, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this library; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18  */
  19 #include "avformat.h"
  20 #include "avi.h"
  21 #include "dv.h"
  22
  23 //#define DEBUG
  24 //#define DEBUG_SEEK
  25
  26 typedef struct AVIIndexEntry {
  27     unsigned int flags;
  28     unsigned int pos;
  29     unsigned int cum_len; /* sum of all lengths before this packet */
  30 } AVIIndexEntry;
  31
  32 typedef struct AVIStream {
  33     AVIIndexEntry *index_entries;
  34     int nb_index_entries;
  35     int index_entries_allocated_size;
  36     int frame_offset; /* current frame (video) or byte (audio) counter
  37                          (used to compute the pts) */
  38     int scale;
  39     int rate;
  40     int sample_size; /* audio only data */
  41     int start;
  42
  43     int new_frame_offset; /* temporary storage (used during seek) */
  44     int cum_len; /* temporary storage (used during seek) */
  45
  46     int prefix;                       ///< normally 'd'<<8 + 'c' or 'w'<<8 + 'b'
  47     int prefix_count;
  48 } AVIStream;
  49
  50 typedef struct {
  51     int64_t  riff_end;
  52     int64_t  movi_end;
  53     offset_t movi_list;
  54     int index_loaded;
  55     int is_odml;
  56     DVDemuxContext* dv_demux;
  57 } AVIContext;
  58
  59 static int avi_load_index(AVFormatContext *s);
  60
  61 #ifdef DEBUG
  62 static void print_tag(const char *str, unsigned int tag, int size)
  63 {
  64     printf("%s: tag=%c%c%c%c size=0x%x\n",
  65            str, tag & 0xff,
  66            (tag >> 8) & 0xff,
  67            (tag >> 16) & 0xff,
  68            (tag >> 24) & 0xff,
  69            size);
  70 }
  71 #endif
  72
  73 static int get_riff(AVIContext *avi, ByteIOContext *pb)
  74 {
  75     uint32_t tag;
  76     /* check RIFF header */
  77     tag = get_le32(pb);
  78
  79     if (tag != MKTAG('R', 'I', 'F', 'F'))
  80         return -1;
  81     avi->riff_end = get_le32(pb);   /* RIFF chunk size */
  82     avi->riff_end += url_ftell(pb); /* RIFF chunk end */
  83     tag = get_le32(pb);
  84     if (tag != MKTAG('A', 'V', 'I', ' ') && tag != MKTAG('A', 'V', 'I', 'X'))
  85         return -1;
  86
  87     return 0;
  88 }
  89
  90 static int avi_read_header(AVFormatContext *s, AVFormatParameters *ap)
  91 {
  92     AVIContext *avi = s->priv_data;
  93     ByteIOContext *pb = &s->pb;
  94     uint32_t tag, tag1, handler;
  95     int codec_type, stream_index, frame_period, bit_rate, scale, rate;
  96     unsigned int size, nb_frames;
  97     int i, n;
  98     AVStream *st;
  99     AVIStream *ast;
 100     int xan_video = 0;  /* hack to support Xan A/V */
 101
 102     if (get_riff(avi, pb) < 0)
 103         return -1;
 104
 105     /* first list tag */
 106     stream_index = -1;
 107     codec_type = -1;
 108     frame_period = 0;
 109     for(;;) {
 110         if (url_feof(pb))
 111             goto fail;
 112         tag = get_le32(pb);
 113         size = get_le32(pb);
 114 #ifdef DEBUG
 115         print_tag("tag", tag, size);
 116 #endif
 117
 118         switch(tag) {
 119         case MKTAG('L', 'I', 'S', 'T'):
 120             /* ignored, except when start of video packets */
 121             tag1 = get_le32(pb);
 122 #ifdef DEBUG
 123             print_tag("list", tag1, 0);
 124 #endif
 125             if (tag1 == MKTAG('m', 'o', 'v', 'i')) {
 126                 avi->movi_list = url_ftell(pb) - 4;
 127                 if(size) avi->movi_end = avi->movi_list + size;
 128                 else     avi->movi_end = url_filesize(url_fileno(pb));
 129 #ifdef DEBUG
 130                 printf("movi end=%Lx\n", avi->movi_end);
 131 #endif
 132                 goto end_of_header;
 133             }
 134             break;
 135         case MKTAG('d', 'm', 'l', 'h'):
 136             avi->is_odml = 1;
 137             url_fskip(pb, size + (size & 1));
 138             break;
 139         case MKTAG('a', 'v', 'i', 'h'):
 140             /* avi header */
 141             /* using frame_period is bad idea */
 142             frame_period = get_le32(pb);
 143             bit_rate = get_le32(pb) * 8;
 144             url_fskip(pb, 4 * 4);
 145             n = get_le32(pb);
 146             for(i=0;i<n;i++) {
 147                 AVIStream *ast;
 148                 st = av_new_stream(s, i);
 149                 if (!st)
 150                     goto fail;
 151
 152                 ast = av_mallocz(sizeof(AVIStream));
 153                 if (!ast)
 154                     goto fail;
 155                 st->priv_data = ast;
 156             }
 157             url_fskip(pb, size - 7 * 4);
 158             break;
 159         case MKTAG('s', 't', 'r', 'h'):
 160             /* stream header */
 161             stream_index++;
 162             tag1 = get_le32(pb);
 163             handler = get_le32(pb); /* codec tag */
 164 #ifdef DEBUG
 165         print_tag("strh", tag1, -1);
 166 #endif
 167             switch(tag1) {
 168             case MKTAG('i', 'a', 'v', 's'):
 169             case MKTAG('i', 'v', 'a', 's'):
 170                 /*
 171                  * After some consideration -- I don't think we
 172                  * have to support anything but DV in a type1 AVIs.
 173                  */
 174                 if (s->nb_streams != 1)
 175                     goto fail;
 176
 177                 if (handler != MKTAG('d', 'v', 's', 'd') &&
 178                     handler != MKTAG('d', 'v', 'h', 'd') &&
 179                     handler != MKTAG('d', 'v', 's', 'l'))
 180                    goto fail;
 181
 182                 av_freep(&s->streams[0]->codec.extradata);
 183                 av_freep(&s->streams[0]);
 184                 s->nb_streams = 0;
 185                 avi->dv_demux = dv_init_demux(s);
 186                 if (!avi->dv_demux)
 187                     goto fail;
 188                 stream_index = s->nb_streams - 1;
 189                 url_fskip(pb, size - 8);
 190                 break;
 191             case MKTAG('v', 'i', 'd', 's'):
 192                 codec_type = CODEC_TYPE_VIDEO;
 193
 194                 if (stream_index >= s->nb_streams) {
 195                     url_fskip(pb, size - 8);
 196                     break;
 197                 }
 198
 199                 st = s->streams[stream_index];
 200                 ast = st->priv_data;
 201                 st->codec.stream_codec_tag= handler;
 202
 203                 get_le32(pb); /* flags */
 204                 get_le16(pb); /* priority */
 205                 get_le16(pb); /* language */
 206                 get_le32(pb); /* XXX: initial frame ? */
 207                 scale = get_le32(pb); /* scale */
 208                 rate = get_le32(pb); /* rate */
 209
 210                 if(scale && rate){
 211                 }else if(frame_period){
 212                     rate = 1000000;
 213                     scale = frame_period;
 214                 }else{
 215                     rate = 25;
 216                     scale = 1;
 217                 }
 218                 ast->rate = rate;
 219                 ast->scale = scale;
 220                 av_set_pts_info(st, 64, scale, rate);
 221                 st->codec.frame_rate = rate;
 222                 st->codec.frame_rate_base = scale;
 223                 get_le32(pb); /* start */
 224                 nb_frames = get_le32(pb);
 225                 st->start_time = 0;
 226                 st->duration = av_rescale(nb_frames,
 227                     st->codec.frame_rate_base * AV_TIME_BASE,
 228                     st->codec.frame_rate);
 229                 url_fskip(pb, size - 9 * 4);
 230                 break;
 231             case MKTAG('a', 'u', 'd', 's'):
 232                 {
 233                     unsigned int length;
 234
 235                     codec_type = CODEC_TYPE_AUDIO;
 236
 237                     if (stream_index >= s->nb_streams) {
 238                         url_fskip(pb, size - 8);
 239                         break;
 240                     }
 241                     st = s->streams[stream_index];
 242                     ast = st->priv_data;
 243
 244                     get_le32(pb); /* flags */
 245                     get_le16(pb); /* priority */
 246                     get_le16(pb); /* language */
 247                     get_le32(pb); /* initial frame */
 248                     ast->scale = get_le32(pb); /* scale */
 249                     ast->rate = get_le32(pb);
 250                     av_set_pts_info(st, 64, ast->scale, ast->rate);
 251                     ast->start= get_le32(pb); /* start */
 252                     length = get_le32(pb); /* length, in samples or bytes */
 253                     get_le32(pb); /* buffer size */
 254                     get_le32(pb); /* quality */
 255                     ast->sample_size = get_le32(pb); /* sample ssize */
 256 //av_log(NULL, AV_LOG_DEBUG, "%d %d %d %d\n", ast->scale, ast->rate, ast->sample_size, ast->start);
 257                     st->start_time = 0;
 258                     if (ast->rate != 0)
 259                         st->duration = (int64_t)length * AV_TIME_BASE / ast->rate;
 260                     url_fskip(pb, size - 12 * 4);
 261                 }
 262                 break;
 263             case MKTAG('t', 'x', 't', 's'):
 264                 //FIXME
 265                 codec_type = CODEC_TYPE_DATA; //CODEC_TYPE_SUB ?  FIXME
 266                 url_fskip(pb, size - 8);
 267                 break;
 268             default:
 269                 goto fail;
 270             }
 271             break;
 272         case MKTAG('s', 't', 'r', 'f'):
 273             /* stream header */
 274             if (stream_index >= s->nb_streams || avi->dv_demux) {
 275                 url_fskip(pb, size);
 276             } else {
 277                 st = s->streams[stream_index];
 278                 switch(codec_type) {
 279                 case CODEC_TYPE_VIDEO:
 280                     get_le32(pb); /* size */
 281                     st->codec.width = get_le32(pb);
 282                     st->codec.height = get_le32(pb);
 283                     get_le16(pb); /* panes */
 284                     st->codec.bits_per_sample= get_le16(pb); /* depth */
 285                     tag1 = get_le32(pb);
 286                     get_le32(pb); /* ImageSize */
 287                     get_le32(pb); /* XPelsPerMeter */
 288                     get_le32(pb); /* YPelsPerMeter */
 289                     get_le32(pb); /* ClrUsed */
 290                     get_le32(pb); /* ClrImportant */
 291
 292                     st->codec.extradata_size= size - 10*4;
 293                     st->codec.extradata= av_malloc(st->codec.extradata_size);
 294                     get_buffer(pb, st->codec.extradata, st->codec.extradata_size);
 295
 296                     if(st->codec.extradata_size & 1) //FIXME check if the encoder really did this correctly
 297                         get_byte(pb);
 298
 299                     /* Extract palette from extradata if bpp <= 8 */
 300                     /* This code assumes that extradata contains only palette */
 301                     /* This is true for all paletted codecs implemented in ffmpeg */
 302                     if (st->codec.extradata_size && (st->codec.bits_per_sample <= 8)) {
 303                         st->codec.palctrl = av_mallocz(sizeof(AVPaletteControl));
 304 #ifdef WORDS_BIGENDIAN
 305                         for (i = 0; i < FFMIN(st->codec.extradata_size, AVPALETTE_SIZE)/4; i++)
 306                             st->codec.palctrl->palette[i] = bswap_32(((uint32_t*)st->codec.extradata)[i]);
 307 #else
 308                         memcpy(st->codec.palctrl->palette, st->codec.extradata,
 309                                FFMIN(st->codec.extradata_size, AVPALETTE_SIZE));
 310 #endif
 311                         st->codec.palctrl->palette_changed = 1;
 312                     }
 313
 314 #ifdef DEBUG
 315                     print_tag("video", tag1, 0);
 316 #endif
 317                     st->codec.codec_type = CODEC_TYPE_VIDEO;
 318                     st->codec.codec_tag = tag1;
 319                     st->codec.codec_id = codec_get_id(codec_bmp_tags, tag1);
 320                     if (st->codec.codec_id == CODEC_ID_XAN_WC4)
 321                         xan_video = 1;
 322 //                    url_fskip(pb, size - 5 * 4);
 323                     break;
 324                 case CODEC_TYPE_AUDIO:
 325                     get_wav_header(pb, &st->codec, size);
 326                     if (size%2) /* 2-aligned (fix for Stargate SG-1 - 3x18 - Shades of Grey.avi) */
 327                         url_fskip(pb, 1);
 328                     /* special case time: To support Xan DPCM, hardcode
 329                      * the format if Xxan is the video codec */
 330                     st->need_parsing = 1;
 331                     /* force parsing as several audio frames can be in
 332                        one packet */
 333                     if (xan_video)
 334                         st->codec.codec_id = CODEC_ID_XAN_DPCM;
 335                     break;
 336                 default:
 337                     st->codec.codec_type = CODEC_TYPE_DATA;
 338                     st->codec.codec_id= CODEC_ID_NONE;
 339                     st->codec.codec_tag= 0;
 340                     url_fskip(pb, size);
 341                     break;
 342                 }
 343             }
 344             break;
 345         default:
 346             /* skip tag */
 347             size += (size & 1);
 348             url_fskip(pb, size);
 349             break;
 350         }
 351     }
 352  end_of_header:
 353     /* check stream number */
 354     if (stream_index != s->nb_streams - 1) {
 355     fail:
 356         for(i=0;i<s->nb_streams;i++) {
 357             av_freep(&s->streams[i]->codec.extradata);
 358             av_freep(&s->streams[i]);
 359         }
 360         return -1;
 361     }
 362
 363     assert(!avi->index_loaded);
 364     avi_load_index(s);
 365     avi->index_loaded = 1;
 366
 367     return 0;
 368 }
 369
 370 static int avi_read_packet(AVFormatContext *s, AVPacket *pkt)
 371 {
 372     AVIContext *avi = s->priv_data;
 373     ByteIOContext *pb = &s->pb;
 374     int n, d[8], size;
 375     offset_t i;
 376     void* dstr;
 377
 378     memset(d, -1, sizeof(int)*8);
 379
 380     if (avi->dv_demux) {
 381         size = dv_get_packet(avi->dv_demux, pkt);
 382         if (size >= 0)
 383             return size;
 384     }
 385
 386     for(i=url_ftell(pb); !url_feof(pb); i++) {
 387         int j;
 388
 389         if (i >= avi->movi_end) {
 390             if (avi->is_odml) {
 391                 url_fskip(pb, avi->riff_end - i);
 392                 avi->riff_end = avi->movi_end = url_filesize(url_fileno(pb));
 393             } else
 394                 break;
 395         }
 396
 397         for(j=0; j<7; j++)
 398             d[j]= d[j+1];
 399         d[7]= get_byte(pb);
 400
 401         size= d[4] + (d[5]<<8) + (d[6]<<16) + (d[7]<<24);
 402
 403         if(    d[2] >= '0' && d[2] <= '9'
 404             && d[3] >= '0' && d[3] <= '9'){
 405             n= (d[2] - '0') * 10 + (d[3] - '0');
 406         }else{
 407             n= 100; //invalid stream id
 408         }
 409 //av_log(NULL, AV_LOG_DEBUG, "%X %X %X %X %X %X %X %X %lld %d %d\n", d[0], d[1], d[2], d[3], d[4], d[5], d[6], d[7], i, size, n);
 410         if(i + size > avi->movi_end || d[0]<0)
 411             continue;
 412
 413         //parse ix##
 414         if(  (d[0] == 'i' && d[1] == 'x' && n < s->nb_streams)
 415         //parse JUNK
 416            ||(d[0] == 'J' && d[1] == 'U' && d[2] == 'N' && d[3] == 'K')){
 417             url_fskip(pb, size);
 418             i+= size;
 419             memset(d, -1, sizeof(int)*8);
 420 //av_log(NULL, AV_LOG_DEBUG, "SKIP\n");
 421             continue;
 422         }
 423
 424         if(    d[0] >= '0' && d[0] <= '9'
 425             && d[1] >= '0' && d[1] <= '9'){
 426             n= (d[0] - '0') * 10 + (d[1] - '0');
 427         }else{
 428             n= 100; //invalid stream id
 429         }
 430
 431         //parse ##dc/##wb
 432         if(n < s->nb_streams){
 433           AVStream *st;
 434           AVIStream *ast;
 435           st = s->streams[n];
 436           ast = st->priv_data;
 437
 438           if(   (ast->prefix_count<5 && d[2]<128 && d[3]<128) ||
 439                 d[2]*256+d[3] == ast->prefix /*||
 440                 (d[2] == 'd' && d[3] == 'c') ||
 441                 (d[2] == 'w' && d[3] == 'b')*/) {
 442
 443 //av_log(NULL, AV_LOG_DEBUG, "OK\n");
 444             if(d[2]*256+d[3] == ast->prefix)
 445                 ast->prefix_count++;
 446             else{
 447                 ast->prefix= d[2]*256+d[3];
 448                 ast->prefix_count= 0;
 449             }
 450
 451             av_new_packet(pkt, size);
 452             get_buffer(pb, pkt->data, size);
 453             if (size & 1) {
 454                 get_byte(pb);
 455                 size++;
 456             }
 457
 458             if (avi->dv_demux) {
 459                 dstr = pkt->destruct;
 460                 size = dv_produce_packet(avi->dv_demux, pkt,
 461                                          pkt->data, pkt->size);
 462                 pkt->destruct = dstr;
 463                 pkt->flags |= PKT_FLAG_KEY;
 464             } else {
 465                 /* XXX: how to handle B frames in avi ? */
 466                 pkt->dts = ast->frame_offset;
 467 //                pkt->dts += ast->start;
 468                 if(ast->sample_size)
 469                     pkt->dts /= ast->sample_size;
 470 //av_log(NULL, AV_LOG_DEBUG, "dts:%Ld offset:%d %d/%d smpl_siz:%d base:%d st:%d size:%d\n", pkt->dts, ast->frame_offset, ast->scale, ast->rate, ast->sample_size, AV_TIME_BASE, n, size);
 471                 pkt->stream_index = n;
 472                 /* FIXME: We really should read index for that */
 473                 if (st->codec.codec_type == CODEC_TYPE_VIDEO) {
 474                     if (ast->frame_offset < ast->nb_index_entries) {
 475                         if (ast->index_entries[ast->frame_offset].flags & AVIIF_INDEX)
 476                             pkt->flags |= PKT_FLAG_KEY;
 477                     } else {
 478                         /* if no index, better to say that all frames
 479                            are key frames */
 480                         pkt->flags |= PKT_FLAG_KEY;
 481                     }
 482                 } else {
 483                     pkt->flags |= PKT_FLAG_KEY;
 484                 }
 485                 if(ast->sample_size)
 486                     ast->frame_offset += pkt->size;
 487                 else
 488                     ast->frame_offset++;
 489             }
 490             return size;
 491           }
 492         }
 493         /* palette changed chunk */
 494         if (   d[0] >= '0' && d[0] <= '9'
 495             && d[1] >= '0' && d[1] <= '9'
 496             && ((d[2] == 'p' && d[3] == 'c'))
 497             && n < s->nb_streams && i + size <= avi->movi_end) {
 498
 499             AVStream *st;
 500             int first, clr, flags, k, p;
 501
 502             st = s->streams[n];
 503
 504             first = get_byte(pb);
 505             clr = get_byte(pb);
 506             flags = get_le16(pb);
 507             p = 4;
 508             for (k = first; k < clr + first; k++) {
 509                 int r, g, b;
 510                 r = get_byte(pb);
 511                 g = get_byte(pb);
 512                 b = get_byte(pb);
 513                     get_byte(pb);
 514                 st->codec.palctrl->palette[k] = b + (g << 8) + (r << 16);
 515             }
 516             st->codec.palctrl->palette_changed = 1;
 517         }
 518
 519     }
 520
 521     return -1;
 522 }
 523
 524 /* XXX: we make the implicit supposition that the position are sorted
 525    for each stream */
 526 static int avi_read_idx1(AVFormatContext *s, int size)
 527 {
 528     ByteIOContext *pb = &s->pb;
 529     int nb_index_entries, i;
 530     AVStream *st;
 531     AVIStream *ast;
 532     AVIIndexEntry *ie, *entries;
 533     unsigned int index, tag, flags, pos, len;
 534
 535     nb_index_entries = size / 16;
 536     if (nb_index_entries <= 0)
 537         return -1;
 538
 539     /* read the entries and sort them in each stream component */
 540     for(i = 0; i < nb_index_entries; i++) {
 541         tag = get_le32(pb);
 542         flags = get_le32(pb);
 543         pos = get_le32(pb);
 544         len = get_le32(pb);
 545 #if defined(DEBUG_SEEK) && 0
 546         printf("%d: tag=0x%x flags=0x%x pos=0x%x len=%d\n",
 547                i, tag, flags, pos, len);
 548 #endif
 549         index = ((tag & 0xff) - '0') * 10;
 550         index += ((tag >> 8) & 0xff) - '0';
 551         if (index >= s->nb_streams)
 552             continue;
 553         st = s->streams[index];
 554         ast = st->priv_data;
 555
 556         entries = av_fast_realloc(ast->index_entries,
 557                                   &ast->index_entries_allocated_size,
 558                                   (ast->nb_index_entries + 1) *
 559                                   sizeof(AVIIndexEntry));
 560         if (entries) {
 561             ast->index_entries = entries;
 562             ie = &entries[ast->nb_index_entries++];
 563             ie->flags = flags;
 564             ie->pos = pos;
 565             ie->cum_len = ast->cum_len;
 566             ast->cum_len += len;
 567         }
 568     }
 569     return 0;
 570 }
 571
 572 static int avi_load_index(AVFormatContext *s)
 573 {
 574     AVIContext *avi = s->priv_data;
 575     ByteIOContext *pb = &s->pb;
 576     uint32_t tag, size;
 577     offset_t pos= url_ftell(pb);
 578
 579     url_fseek(pb, avi->movi_end, SEEK_SET);
 580 #ifdef DEBUG_SEEK
 581     printf("movi_end=0x%llx\n", avi->movi_end);
 582 #endif
 583     for(;;) {
 584         if (url_feof(pb))
 585             break;
 586         tag = get_le32(pb);
 587         size = get_le32(pb);
 588 #ifdef DEBUG_SEEK
 589         printf("tag=%c%c%c%c size=0x%x\n",
 590                tag & 0xff,
 591                (tag >> 8) & 0xff,
 592                (tag >> 16) & 0xff,
 593                (tag >> 24) & 0xff,
 594                size);
 595 #endif
 596         switch(tag) {
 597         case MKTAG('i', 'd', 'x', '1'):
 598             if (avi_read_idx1(s, size) < 0)
 599                 goto skip;
 600             else
 601                 goto the_end;
 602             break;
 603         default:
 604         skip:
 605             size += (size & 1);
 606             url_fskip(pb, size);
 607             break;
 608         }
 609     }
 610  the_end:
 611     url_fseek(pb, pos, SEEK_SET);
 612     return 0;
 613 }
 614
 615 /* return the index entry whose position is immediately >= 'wanted_pos' */
 616 static int locate_frame_in_index(AVIIndexEntry *entries,
 617                                  int nb_entries, int wanted_pos)
 618 {
 619     int a, b, m, pos;
 620
 621     a = 0;
 622     b = nb_entries - 1;
 623     while (a <= b) {
 624         m = (a + b) >> 1;
 625         pos = entries[m].pos;
 626         if (pos == wanted_pos)
 627             goto found;
 628         else if (pos > wanted_pos) {
 629             b = m - 1;
 630         } else {
 631             a = m + 1;
 632         }
 633     }
 634     m = a;
 635     if (m > 0)
 636         m--;
 637  found:
 638     return m;
 639 }
 640
 641 static int avi_read_seek(AVFormatContext *s, int stream_index, int64_t timestamp)
 642 {
 643     AVIContext *avi = s->priv_data;
 644     AVStream *st;
 645     AVIStream *ast;
 646     int frame_number, i;
 647     int64_t pos;
 648
 649     if (!avi->index_loaded) {
 650         /* we only load the index on demand */
 651         avi_load_index(s);
 652         avi->index_loaded = 1;
 653     }
 654     if (stream_index < 0) {
 655         for(i = 0; i < s->nb_streams; i++) {
 656             st = s->streams[i];
 657             if (st->codec.codec_type == CODEC_TYPE_VIDEO)
 658                 goto found;
 659         }
 660         return -1;
 661     found:
 662         stream_index = i;
 663     }
 664
 665     st = s->streams[stream_index];
 666     if (st->codec.codec_type != CODEC_TYPE_VIDEO)
 667         return -1;
 668     ast = st->priv_data;
 669     /* compute the frame number */
 670     frame_number = timestamp;
 671 #ifdef DEBUG_SEEK
 672     printf("timestamp=%0.3f nb_indexes=%d frame_number=%d\n",
 673            (double)timestamp / AV_TIME_BASE,
 674            ast->nb_index_entries, frame_number);
 675 #endif
 676     /* find a closest key frame before */
 677     if (frame_number >= ast->nb_index_entries)
 678         return -1;
 679     while (frame_number >= 0 &&
 680            !(ast->index_entries[frame_number].flags & AVIIF_INDEX))
 681         frame_number--;
 682     if (frame_number < 0)
 683         return -1;
 684     ast->new_frame_offset = frame_number;
 685
 686     /* find the position */
 687     pos = ast->index_entries[frame_number].pos;
 688
 689 #ifdef DEBUG_SEEK
 690     printf("key_frame_number=%d pos=0x%llx\n",
 691            frame_number, pos);
 692 #endif
 693
 694     /* update the frame counters for all the other stream by looking
 695        at the positions just after the one found */
 696     for(i = 0; i < s->nb_streams; i++) {
 697         int j;
 698         if (i != stream_index) {
 699             st = s->streams[i];
 700             ast = st->priv_data;
 701             if (ast->nb_index_entries <= 0)
 702                 return -1;
 703             j = locate_frame_in_index(ast->index_entries,
 704                                       ast->nb_index_entries,
 705                                       pos);
 706             /* get next frame */
 707             if ((j  + 1) < ast->nb_index_entries)
 708                 j++;
 709             /* extract the current frame number */
 710             if (ast->sample_size==0)
 711                 ast->new_frame_offset = j;
 712             else
 713                 ast->new_frame_offset = ast->index_entries[j].cum_len;
 714         }
 715     }
 716
 717     /* everything is OK now. We can update the frame offsets */
 718     for(i = 0; i < s->nb_streams; i++) {
 719         st = s->streams[i];
 720         ast = st->priv_data;
 721         ast->frame_offset = ast->new_frame_offset;
 722 #ifdef DEBUG_SEEK
 723         printf("%d: frame_offset=%d\n", i,
 724                ast->frame_offset);
 725 #endif
 726     }
 727     /* do the seek */
 728     pos += avi->movi_list;
 729     url_fseek(&s->pb, pos, SEEK_SET);
 730     return 0;
 731 }
 732
 733 static int avi_read_close(AVFormatContext *s)
 734 {
 735     int i;
 736     AVIContext *avi = s->priv_data;
 737
 738     for(i=0;i<s->nb_streams;i++) {
 739         AVStream *st = s->streams[i];
 740         AVIStream *ast = st->priv_data;
 741         if(ast){
 742             av_free(ast->index_entries);
 743             av_free(ast);
 744         }
 745         av_free(st->codec.extradata);
 746         av_free(st->codec.palctrl);
 747     }
 748
 749     if (avi->dv_demux)
 750         av_free(avi->dv_demux);
 751
 752     return 0;
 753 }
 754
 755 static int avi_probe(AVProbeData *p)
 756 {
 757     /* check file header */
 758     if (p->buf_size <= 32)
 759         return 0;
 760     if (p->buf[0] == 'R' && p->buf[1] == 'I' &&
 761         p->buf[2] == 'F' && p->buf[3] == 'F' &&
 762         p->buf[8] == 'A' && p->buf[9] == 'V' &&
 763         p->buf[10] == 'I' && p->buf[11] == ' ')
 764         return AVPROBE_SCORE_MAX;
 765     else
 766         return 0;
 767 }
 768
 769 static AVInputFormat avi_iformat = {
 770     "avi",
 771     "avi format",
 772     sizeof(AVIContext),
 773     avi_probe,
 774     avi_read_header,
 775     avi_read_packet,
 776     avi_read_close,
 777     avi_read_seek,
 778 };
 779
 780 int avidec_init(void)
 781 {
 782     av_register_input_format(&avi_iformat);
 783     return 0;
 784 }