git.sesse.net Git - vlc/blob - modules/packetizer/mpegvideo.c

   1 /*****************************************************************************
   2  * mpegvideo.c: parse and packetize an MPEG1/2 video stream
   3  *****************************************************************************
   4  * Copyright (C) 2001-2006 the VideoLAN team
   5  * $Id$
   6  *
   7  * Authors: Laurent Aimar <fenrir@via.ecp.fr>
   8  *          Eric Petit <titer@videolan.org>
   9  *          Gildas Bazin <gbazin@videolan.org>
  10  *          Jean-Paul Saman <jpsaman #_at_# m2x dot nl>
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  25  *****************************************************************************/
  26
  27 /*****************************************************************************
  28  * Problem with this implementation:
  29  *
  30  * Although we should time-stamp each picture with a PTS, this isn't possible
  31  * with the current implementation.
  32  * The problem comes from the fact that for non-low-delay streams we can't
  33  * calculate the PTS of pictures used as backward reference. Even the temporal
  34  * reference number doesn't help here because all the pictures don't
  35  * necessarily have the same duration (eg. 3:2 pulldown).
  36  *
  37  * However this doesn't really matter as far as the MPEG muxers are concerned
  38  * because they allow having empty PTS fields. --gibalou
  39  *****************************************************************************/
  40
  41 /*****************************************************************************
  42  * Preamble
  43  *****************************************************************************/
  44 #include <stdlib.h>                                      /* malloc(), free() */
  45
  46 #include <vlc/vlc.h>
  47 #include <vlc_block.h>
  48 #include <vlc_codec.h>
  49 #include <vlc_block_helper.h>
  50
  51 #define SYNC_INTRAFRAME_TEXT N_("Sync on Intra Frame")
  52 #define SYNC_INTRAFRAME_LONGTEXT N_("Normally the packetizer would " \
  53     "sync on the next full frame. This flags instructs the packetizer " \
  54     "to sync on the first Intra Frame found.")
  55
  56 /*****************************************************************************
  57  * Module descriptor
  58  *****************************************************************************/
  59 static int  Open ( vlc_object_t * );
  60 static void Close( vlc_object_t * );
  61
  62 vlc_module_begin();
  63     set_category( CAT_SOUT );
  64     set_subcategory( SUBCAT_SOUT_PACKETIZER );
  65     set_description( _("MPEG-I/II video packetizer") );
  66     set_capability( "packetizer", 50 );
  67     set_callbacks( Open, Close );
  68
  69     add_bool( "packetizer-mpegvideo-sync-iframe", 0, NULL, SYNC_INTRAFRAME_TEXT,
  70               SYNC_INTRAFRAME_LONGTEXT, VLC_TRUE );
  71 vlc_module_end();
  72
  73 /*****************************************************************************
  74  * Local prototypes
  75  *****************************************************************************/
  76 static block_t *Packetize( decoder_t *, block_t ** );
  77 static block_t *ParseMPEGBlock( decoder_t *, block_t * );
  78
  79 struct decoder_sys_t
  80 {
  81     /*
  82      * Input properties
  83      */
  84     block_bytestream_t bytestream;
  85     int i_state;
  86     int i_offset;
  87     uint8_t p_startcode[3];
  88
  89     /* Sequence header and extension */
  90     block_t *p_seq;
  91     block_t *p_ext;
  92
  93     /* Current frame being built */
  94     block_t    *p_frame;
  95     block_t    **pp_last;
  96
  97     vlc_bool_t b_frame_slice;
  98     mtime_t i_pts;
  99     mtime_t i_dts;
 100
 101     /* Sequence properties */
 102     int         i_frame_rate;
 103     int         i_frame_rate_base;
 104     vlc_bool_t  b_seq_progressive;
 105     vlc_bool_t  b_low_delay;
 106     int         i_aspect_ratio_info;
 107     vlc_bool_t  b_inited;
 108
 109     /* Picture properties */
 110     int i_temporal_ref;
 111     int i_picture_type;
 112     int i_picture_structure;
 113     int i_top_field_first;
 114     int i_repeat_first_field;
 115     int i_progressive_frame;
 116
 117     mtime_t i_interpolated_dts;
 118     mtime_t i_last_ref_pts;
 119     vlc_bool_t b_second_field;
 120
 121     /* Number of pictures since last sequence header */
 122     int i_seq_old;
 123
 124     /* Sync behaviour */
 125     vlc_bool_t  b_sync_on_intra_frame;
 126     vlc_bool_t  b_discontinuity;
 127 };
 128
 129 enum {
 130     STATE_NOSYNC,
 131     STATE_NEXT_SYNC
 132 };
 133
 134 /*****************************************************************************
 135  * Open:
 136  *****************************************************************************/
 137 static int Open( vlc_object_t *p_this )
 138 {
 139     decoder_t *p_dec = (decoder_t*)p_this;
 140     decoder_sys_t *p_sys;
 141
 142     if( p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', '1' ) &&
 143         p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', '2' ) &&
 144         p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', 'v' ) )
 145     {
 146         return VLC_EGENERIC;
 147     }
 148
 149     es_format_Init( &p_dec->fmt_out, VIDEO_ES, VLC_FOURCC('m','p','g','v') );
 150     p_dec->pf_packetize = Packetize;
 151
 152     p_dec->p_sys = p_sys = malloc( sizeof( decoder_sys_t ) );
 153
 154     /* Misc init */
 155     p_sys->i_state = STATE_NOSYNC;
 156     p_sys->bytestream = block_BytestreamInit( p_dec );
 157     p_sys->p_startcode[0] = 0;
 158     p_sys->p_startcode[1] = 0;
 159     p_sys->p_startcode[2] = 1;
 160     p_sys->i_offset = 0;
 161
 162     p_sys->p_seq = NULL;
 163     p_sys->p_ext = NULL;
 164     p_sys->p_frame = NULL;
 165     p_sys->pp_last = &p_sys->p_frame;
 166     p_sys->b_frame_slice = VLC_FALSE;
 167
 168     p_sys->i_dts = p_sys->i_pts = 0;
 169
 170     p_sys->i_frame_rate = 1;
 171     p_sys->i_frame_rate_base = 1;
 172     p_sys->b_seq_progressive = VLC_TRUE;
 173     p_sys->b_low_delay = VLC_TRUE;
 174     p_sys->i_seq_old = 0;
 175
 176     p_sys->i_temporal_ref = 0;
 177     p_sys->i_picture_type = 0;
 178     p_sys->i_picture_structure = 0x03; /* frame */
 179     p_sys->i_top_field_first = 0;
 180     p_sys->i_repeat_first_field = 0;
 181     p_sys->i_progressive_frame = 0;
 182     p_sys->b_inited = 0;
 183
 184     p_sys->i_interpolated_dts = 0;
 185     p_sys->i_last_ref_pts = 0;
 186     p_sys->b_second_field = 0;
 187
 188     p_sys->b_discontinuity = VLC_FALSE;
 189     p_sys->b_sync_on_intra_frame = var_CreateGetBool( p_dec, "packetizer-mpegvideo-sync-iframe" );
 190     if( p_sys->b_sync_on_intra_frame )
 191         msg_Dbg( p_dec, "syncing on intra frame now" );
 192
 193     return VLC_SUCCESS;
 194 }
 195
 196 /*****************************************************************************
 197  * Close:
 198  *****************************************************************************/
 199 static void Close( vlc_object_t *p_this )
 200 {
 201     decoder_t     *p_dec = (decoder_t*)p_this;
 202     decoder_sys_t *p_sys = p_dec->p_sys;
 203
 204     block_BytestreamRelease( &p_sys->bytestream );
 205
 206     if( p_sys->p_seq )
 207     {
 208         block_Release( p_sys->p_seq );
 209     }
 210     if( p_sys->p_ext )
 211     {
 212         block_Release( p_sys->p_ext );
 213     }
 214     if( p_sys->p_frame )
 215     {
 216         block_ChainRelease( p_sys->p_frame );
 217     }
 218
 219     var_Destroy( p_dec, "packetizer-mpegvideo-sync-iframe" );
 220
 221     free( p_sys );
 222 }
 223
 224 /*****************************************************************************
 225  * Packetize:
 226  *****************************************************************************/
 227 static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
 228 {
 229     decoder_sys_t *p_sys = p_dec->p_sys;
 230     block_t       *p_pic;
 231
 232     if( pp_block == NULL || *pp_block == NULL )
 233     {
 234         return NULL;
 235     }
 236
 237     if( (*pp_block)->i_flags&(BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 238     {
 239         if( (*pp_block)->i_flags&BLOCK_FLAG_CORRUPTED )
 240         {
 241             p_sys->i_state = STATE_NOSYNC;
 242             block_BytestreamFlush( &p_sys->bytestream );
 243
 244             p_sys->b_discontinuity = VLC_TRUE;
 245             if( p_sys->p_frame )
 246                 block_ChainRelease( p_sys->p_frame );
 247             p_sys->p_frame = NULL;
 248             p_sys->pp_last = &p_sys->p_frame;
 249             p_sys->b_frame_slice = VLC_FALSE;
 250         }
 251 //        p_sys->i_interpolated_dts =
 252 //        p_sys->i_last_ref_pts = 0;
 253
 254         block_Release( *pp_block );
 255         return NULL;
 256     }
 257
 258
 259     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 260
 261     while( 1 )
 262     {
 263         switch( p_sys->i_state )
 264         {
 265
 266         case STATE_NOSYNC:
 267             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 268                     &p_sys->i_offset, p_sys->p_startcode, 3 ) == VLC_SUCCESS )
 269             {
 270                 p_sys->i_state = STATE_NEXT_SYNC;
 271             }
 272
 273             if( p_sys->i_offset )
 274             {
 275                 block_SkipBytes( &p_sys->bytestream, p_sys->i_offset );
 276                 p_sys->i_offset = 0;
 277                 block_BytestreamFlush( &p_sys->bytestream );
 278             }
 279
 280             if( p_sys->i_state != STATE_NEXT_SYNC )
 281             {
 282                 /* Need more data */
 283                 return NULL;
 284             }
 285
 286             p_sys->i_offset = 1; /* To find next startcode */
 287
 288         case STATE_NEXT_SYNC:
 289             /* TODO: If p_block == NULL, flush the buffer without checking the
 290              * next sync word */
 291
 292             /* Find the next startcode */
 293             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 294                     &p_sys->i_offset, p_sys->p_startcode, 3 ) != VLC_SUCCESS )
 295             {
 296                 /* Need more data */
 297                 return NULL;
 298             }
 299
 300             /* Get the new fragment and set the pts/dts */
 301             p_pic = block_New( p_dec, p_sys->i_offset );
 302             block_BytestreamFlush( &p_sys->bytestream );
 303             p_pic->i_pts = p_sys->bytestream.p_block->i_pts;
 304             p_pic->i_dts = p_sys->bytestream.p_block->i_dts;
 305
 306             block_GetBytes( &p_sys->bytestream, p_pic->p_buffer,
 307                             p_pic->i_buffer );
 308
 309             /* don't reuse the same timestamps several times */
 310             if( p_pic->i_buffer >= 4 && p_pic->p_buffer[3] == 0x00 )
 311             {
 312                 /* We have a picture start code */
 313                 p_sys->bytestream.p_block->i_pts = 0;
 314                 p_sys->bytestream.p_block->i_dts = 0;
 315             }
 316
 317             p_sys->i_offset = 0;
 318
 319             /* Get picture if any */
 320             if( !( p_pic = ParseMPEGBlock( p_dec, p_pic ) ) )
 321             {
 322                 p_sys->i_state = STATE_NOSYNC;
 323                 break;
 324             }
 325
 326             /* If a discontinuity has been encountered, then wait till
 327              * the next Intra frame before continuing with packetizing */
 328             if( p_sys->b_discontinuity &&
 329                 p_sys->b_sync_on_intra_frame )
 330             {
 331                 if( p_pic->i_flags & BLOCK_FLAG_TYPE_I )
 332                 {
 333                     msg_Dbg( p_dec, "synced on intra frame" );
 334                     p_sys->b_discontinuity = VLC_FALSE;
 335                     p_pic->i_flags |= BLOCK_FLAG_DISCONTINUITY;
 336                 }
 337                 else
 338                 {
 339                     msg_Dbg( p_dec, "waiting on intra frame" );
 340                     p_sys->i_state = STATE_NOSYNC;
 341                     block_Release( p_pic );
 342                     break;
 343                 }
 344             }
 345
 346             /* We've just started the stream, wait for the first PTS.
 347              * We discard here so we can still get the sequence header. */
 348             if( p_sys->i_dts <= 0 && p_sys->i_pts <= 0 &&
 349                 p_sys->i_interpolated_dts <= 0 )
 350             {
 351                 msg_Dbg( p_dec, "need a starting pts/dts" );
 352                 p_sys->i_state = STATE_NOSYNC;
 353                 block_Release( p_pic );
 354                 break;
 355             }
 356
 357             /* When starting the stream we can have the first frame with
 358              * a null DTS (i_interpolated_pts is initialized to 0) */
 359             if( !p_pic->i_dts ) p_pic->i_dts = p_pic->i_pts;
 360
 361             /* So p_block doesn't get re-added several times */
 362             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 363
 364             p_sys->i_state = STATE_NOSYNC;
 365
 366             return p_pic;
 367         }
 368     }
 369 }
 370
 371 /*****************************************************************************
 372  * ParseMPEGBlock: Re-assemble fragments into a block containing a picture
 373  *****************************************************************************/
 374 static block_t *ParseMPEGBlock( decoder_t *p_dec, block_t *p_frag )
 375 {
 376     decoder_sys_t *p_sys = p_dec->p_sys;
 377     block_t *p_pic = NULL;
 378
 379     /*
 380      * Check if previous picture is finished
 381      */
 382     if( ( p_sys->b_frame_slice &&
 383           (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) ) &&
 384           p_sys->p_seq == NULL )
 385     {
 386         /* We have a picture but without a sequence header we can't
 387          * do anything */
 388         msg_Dbg( p_dec, "waiting for sequence start" );
 389         if( p_sys->p_frame ) block_ChainRelease( p_sys->p_frame );
 390         p_sys->p_frame = NULL;
 391         p_sys->pp_last = &p_sys->p_frame;
 392         p_sys->b_frame_slice = VLC_FALSE;
 393
 394     }
 395     else if( p_sys->b_frame_slice &&
 396              (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) )
 397     {
 398         mtime_t i_duration;
 399
 400         p_pic = block_ChainGather( p_sys->p_frame );
 401
 402         i_duration = (mtime_t)( 1000000 * p_sys->i_frame_rate_base /
 403                                 p_sys->i_frame_rate );
 404
 405         if( !p_sys->b_seq_progressive && p_sys->i_picture_structure != 0x03 )
 406         {
 407             i_duration /= 2;
 408         }
 409
 410         if( p_sys->b_seq_progressive )
 411         {
 412             if( p_sys->i_top_field_first == 0 &&
 413                 p_sys->i_repeat_first_field == 1 )
 414             {
 415                 i_duration *= 2;
 416             }
 417             else if( p_sys->i_top_field_first == 1 &&
 418                      p_sys->i_repeat_first_field == 1 )
 419             {
 420                 i_duration *= 3;
 421             }
 422         }
 423         else
 424         {
 425             if( p_sys->i_picture_structure == 0x03 )
 426             {
 427                 if( p_sys->i_progressive_frame && p_sys->i_repeat_first_field )
 428                 {
 429                     i_duration += i_duration / 2;
 430                 }
 431             }
 432         }
 433
 434         if( p_sys->b_low_delay || p_sys->i_picture_type == 0x03 )
 435         {
 436             /* Trivial case (DTS == PTS) */
 437             /* Correct interpolated dts when we receive a new pts/dts */
 438             if( p_sys->i_pts > 0 ) p_sys->i_interpolated_dts = p_sys->i_pts;
 439             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 440         }
 441         else
 442         {
 443             /* Correct interpolated dts when we receive a new pts/dts */
 444             if( p_sys->i_last_ref_pts > 0 && !p_sys->b_second_field )
 445                 p_sys->i_interpolated_dts = p_sys->i_last_ref_pts;
 446             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 447
 448             if( !p_sys->b_second_field )
 449                 p_sys->i_last_ref_pts = p_sys->i_pts;
 450         }
 451
 452         p_pic->i_dts = p_sys->i_interpolated_dts;
 453         p_sys->i_interpolated_dts += i_duration;
 454
 455         /* Set PTS only if we have a B frame or if it comes from the stream */
 456         if( p_sys->i_pts > 0 )
 457         {
 458             p_pic->i_pts = p_sys->i_pts;
 459         }
 460         else if( p_sys->i_picture_type == 0x03 )
 461         {
 462             p_pic->i_pts = p_pic->i_dts;
 463         }
 464         else
 465         {
 466             p_pic->i_pts = 0;
 467         }
 468
 469         switch ( p_sys->i_picture_type )
 470         {
 471         case 0x01:
 472             p_pic->i_flags |= BLOCK_FLAG_TYPE_I;
 473             break;
 474         case 0x02:
 475             p_pic->i_flags |= BLOCK_FLAG_TYPE_P;
 476             break;
 477         case 0x03:
 478             p_pic->i_flags |= BLOCK_FLAG_TYPE_B;
 479             break;
 480         }
 481
 482         p_pic->i_length = p_sys->i_interpolated_dts - p_pic->i_dts;
 483
 484 #if 0
 485         msg_Dbg( p_dec, "pic: type=%d dts="I64Fd" pts-dts="I64Fd,
 486         p_sys->i_picture_type, p_pic->i_dts, p_pic->i_pts - p_pic->i_dts);
 487 #endif
 488
 489         /* Reset context */
 490         p_sys->p_frame = NULL;
 491         p_sys->pp_last = &p_sys->p_frame;
 492         p_sys->b_frame_slice = VLC_FALSE;
 493
 494         if( p_sys->i_picture_structure != 0x03 )
 495         {
 496             p_sys->b_second_field = !p_sys->b_second_field;
 497         }
 498         else
 499         {
 500             p_sys->b_second_field = 0;
 501         }
 502     }
 503
 504     /*
 505      * Check info of current fragment
 506      */
 507     if( p_frag->p_buffer[3] == 0xb8 )
 508     {
 509         /* Group start code */
 510         if( p_sys->p_seq &&
 511             p_sys->i_seq_old > p_sys->i_frame_rate/p_sys->i_frame_rate_base )
 512         {
 513             /* Usefull for mpeg1: repeat sequence header every second */
 514             block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_seq ) );
 515             if( p_sys->p_ext )
 516             {
 517                 block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_ext ) );
 518             }
 519
 520             p_sys->i_seq_old = 0;
 521         }
 522     }
 523     else if( p_frag->p_buffer[3] == 0xb3 && p_frag->i_buffer >= 8 )
 524     {
 525         /* Sequence header code */
 526         static const int code_to_frame_rate[16][2] =
 527         {
 528             { 1, 1 },  /* invalid */
 529             { 24000, 1001 }, { 24, 1 }, { 25, 1 },       { 30000, 1001 },
 530             { 30, 1 },       { 50, 1 }, { 60000, 1001 }, { 60, 1 },
 531             /* Unofficial 15fps from Xing*/
 532             { 15, 1001 },
 533             /* Unofficial economy rates from libmpeg3 */
 534             { 5, 1001 }, { 10, 1001 }, { 12, 1001 }, { 15, 1001 },
 535             { 1, 1 },  { 1, 1 }  /* invalid */
 536         };
 537
 538         if( p_sys->p_seq ) block_Release( p_sys->p_seq );
 539         if( p_sys->p_ext ) block_Release( p_sys->p_ext );
 540
 541         p_sys->p_seq = block_Duplicate( p_frag );
 542         p_sys->i_seq_old = 0;
 543         p_sys->p_ext = NULL;
 544
 545         p_dec->fmt_out.video.i_width =
 546             ( p_frag->p_buffer[4] << 4)|(p_frag->p_buffer[5] >> 4 );
 547         p_dec->fmt_out.video.i_height =
 548             ( (p_frag->p_buffer[5]&0x0f) << 8 )|p_frag->p_buffer[6];
 549         p_sys->i_aspect_ratio_info = p_frag->p_buffer[7] >> 4;
 550
 551         /* TODO: MPEG1 aspect ratio */
 552
 553         p_sys->i_frame_rate = code_to_frame_rate[p_frag->p_buffer[7]&0x0f][0];
 554         p_sys->i_frame_rate_base =
 555             code_to_frame_rate[p_frag->p_buffer[7]&0x0f][1];
 556
 557         p_dec->fmt_out.video.i_frame_rate = p_sys->i_frame_rate;
 558         p_dec->fmt_out.video.i_frame_rate_base = p_sys->i_frame_rate_base;
 559
 560         p_sys->b_seq_progressive = VLC_TRUE;
 561         p_sys->b_low_delay = VLC_TRUE;
 562
 563         if ( !p_sys->b_inited )
 564         {
 565             msg_Dbg( p_dec, "size %dx%d fps=%.3f",
 566                  p_dec->fmt_out.video.i_width, p_dec->fmt_out.video.i_height,
 567                  p_sys->i_frame_rate / (float)p_sys->i_frame_rate_base );
 568             p_sys->b_inited = 1;
 569         }
 570     }
 571     else if( p_frag->p_buffer[3] == 0xb5 )
 572     {
 573         int i_type = p_frag->p_buffer[4] >> 4;
 574
 575         /* Extension start code */
 576         if( i_type == 0x01 )
 577         {
 578 #if 0
 579             static const int mpeg2_aspect[16][2] =
 580             {
 581                 {0,1}, {1,1}, {4,3}, {16,9}, {221,100},
 582                 {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1},
 583                 {0,1}, {0,1}
 584             };
 585 #endif
 586
 587             /* sequence extension */
 588             if( p_sys->p_ext) block_Release( p_sys->p_ext );
 589             p_sys->p_ext = block_Duplicate( p_frag );
 590
 591             if( p_frag->i_buffer >= 10 )
 592             {
 593                 p_sys->b_seq_progressive =
 594                     p_frag->p_buffer[5]&0x08 ? VLC_TRUE : VLC_FALSE;
 595                 p_sys->b_low_delay =
 596                     p_frag->p_buffer[9]&0x80 ? VLC_TRUE : VLC_FALSE;
 597             }
 598
 599             /* Do not set aspect ratio : in case we're transcoding,
 600              * transcode will take our fmt_out as a fmt_in to libmpeg2.
 601              * libmpeg2.c will then believe that the user has requested
 602              * a specific aspect ratio, which she hasn't. Thus in case
 603              * of aspect ratio change, we're screwed. --Meuuh
 604              */
 605 #if 0
 606             p_dec->fmt_out.video.i_aspect =
 607                 mpeg2_aspect[p_sys->i_aspect_ratio_info][0] *
 608                 VOUT_ASPECT_FACTOR /
 609                 mpeg2_aspect[p_sys->i_aspect_ratio_info][1];
 610 #endif
 611
 612         }
 613         else if( i_type == 0x08 )
 614         {
 615             /* picture extension */
 616             p_sys->i_picture_structure = p_frag->p_buffer[6]&0x03;
 617             p_sys->i_top_field_first   = p_frag->p_buffer[7] >> 7;
 618             p_sys->i_repeat_first_field= (p_frag->p_buffer[7]>>1)&0x01;
 619             p_sys->i_progressive_frame = p_frag->p_buffer[8] >> 7;
 620         }
 621     }
 622     else if( p_frag->p_buffer[3] == 0x00 )
 623     {
 624         /* Picture start code */
 625         p_sys->i_seq_old++;
 626
 627         if( p_frag->i_buffer >= 6 )
 628         {
 629             p_sys->i_temporal_ref =
 630                 ( p_frag->p_buffer[4] << 2 )|(p_frag->p_buffer[5] >> 6);
 631             p_sys->i_picture_type = ( p_frag->p_buffer[5] >> 3 ) & 0x03;
 632         }
 633
 634         p_sys->i_dts = p_frag->i_dts;
 635         p_sys->i_pts = p_frag->i_pts;
 636     }
 637     else if( p_frag->p_buffer[3] >= 0x01 && p_frag->p_buffer[3] <= 0xaf )
 638     {
 639         /* Slice start code */
 640         p_sys->b_frame_slice = VLC_TRUE;
 641     }
 642
 643     /* Append the block */
 644     block_ChainLastAppend( &p_sys->pp_last, p_frag );
 645
 646     return p_pic;
 647 }