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_old_duration;
 119     mtime_t i_last_ref_pts;
 120     vlc_bool_t b_second_field;
 121
 122     /* Number of pictures since last sequence header */
 123     int i_seq_old;
 124
 125     /* Sync behaviour */
 126     vlc_bool_t  b_sync_on_intra_frame;
 127     vlc_bool_t  b_discontinuity;
 128 };
 129
 130 enum {
 131     STATE_NOSYNC,
 132     STATE_NEXT_SYNC
 133 };
 134
 135 /*****************************************************************************
 136  * Open:
 137  *****************************************************************************/
 138 static int Open( vlc_object_t *p_this )
 139 {
 140     decoder_t *p_dec = (decoder_t*)p_this;
 141     decoder_sys_t *p_sys;
 142
 143     if( p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', '1' ) &&
 144         p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', '2' ) &&
 145         p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', 'v' ) )
 146     {
 147         return VLC_EGENERIC;
 148     }
 149
 150     es_format_Init( &p_dec->fmt_out, VIDEO_ES, VLC_FOURCC('m','p','g','v') );
 151     p_dec->pf_packetize = Packetize;
 152
 153     p_dec->p_sys = p_sys = malloc( sizeof( decoder_sys_t ) );
 154
 155     /* Misc init */
 156     p_sys->i_state = STATE_NOSYNC;
 157     p_sys->bytestream = block_BytestreamInit( p_dec );
 158     p_sys->p_startcode[0] = 0;
 159     p_sys->p_startcode[1] = 0;
 160     p_sys->p_startcode[2] = 1;
 161     p_sys->i_offset = 0;
 162
 163     p_sys->p_seq = NULL;
 164     p_sys->p_ext = NULL;
 165     p_sys->p_frame = NULL;
 166     p_sys->pp_last = &p_sys->p_frame;
 167     p_sys->b_frame_slice = VLC_FALSE;
 168
 169     p_sys->i_dts = p_sys->i_pts = 0;
 170
 171     p_sys->i_frame_rate = 1;
 172     p_sys->i_frame_rate_base = 1;
 173     p_sys->b_seq_progressive = VLC_TRUE;
 174     p_sys->b_low_delay = VLC_TRUE;
 175     p_sys->i_seq_old = 0;
 176
 177     p_sys->i_temporal_ref = 0;
 178     p_sys->i_picture_type = 0;
 179     p_sys->i_picture_structure = 0x03; /* frame */
 180     p_sys->i_top_field_first = 0;
 181     p_sys->i_repeat_first_field = 0;
 182     p_sys->i_progressive_frame = 0;
 183     p_sys->b_inited = 0;
 184
 185     p_sys->i_interpolated_dts = 0;
 186     p_sys->i_old_duration = 0;
 187     p_sys->i_last_ref_pts = 0;
 188     p_sys->b_second_field = 0;
 189
 190     p_sys->b_discontinuity = VLC_FALSE;
 191     p_sys->b_sync_on_intra_frame = var_CreateGetBool( p_dec, "packetizer-mpegvideo-sync-iframe" );
 192     if( p_sys->b_sync_on_intra_frame )
 193         msg_Dbg( p_dec, "syncing on intra frame now" );
 194
 195     return VLC_SUCCESS;
 196 }
 197
 198 /*****************************************************************************
 199  * Close:
 200  *****************************************************************************/
 201 static void Close( vlc_object_t *p_this )
 202 {
 203     decoder_t     *p_dec = (decoder_t*)p_this;
 204     decoder_sys_t *p_sys = p_dec->p_sys;
 205
 206     block_BytestreamRelease( &p_sys->bytestream );
 207
 208     if( p_sys->p_seq )
 209     {
 210         block_Release( p_sys->p_seq );
 211     }
 212     if( p_sys->p_ext )
 213     {
 214         block_Release( p_sys->p_ext );
 215     }
 216     if( p_sys->p_frame )
 217     {
 218         block_ChainRelease( p_sys->p_frame );
 219     }
 220
 221     var_Destroy( p_dec, "packetizer-mpegvideo-sync-iframe" );
 222
 223     free( p_sys );
 224 }
 225
 226 /*****************************************************************************
 227  * Packetize:
 228  *****************************************************************************/
 229 static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
 230 {
 231     decoder_sys_t *p_sys = p_dec->p_sys;
 232     block_t       *p_pic;
 233
 234     if( pp_block == NULL || *pp_block == NULL )
 235     {
 236         return NULL;
 237     }
 238
 239     if( (*pp_block)->i_flags & (BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 240     {
 241         p_sys->i_state = STATE_NOSYNC;
 242         p_sys->b_discontinuity = VLC_TRUE;
 243         if( p_sys->p_frame )
 244             block_ChainRelease( p_sys->p_frame );
 245         p_sys->p_frame = NULL;
 246         p_sys->pp_last = &p_sys->p_frame;
 247         p_sys->b_frame_slice = VLC_FALSE;
 248         block_Release( *pp_block );
 249         return NULL;
 250     }
 251
 252     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 253
 254     while( 1 )
 255     {
 256         switch( p_sys->i_state )
 257         {
 258
 259         case STATE_NOSYNC:
 260             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 261                     &p_sys->i_offset, p_sys->p_startcode, 3 ) == VLC_SUCCESS )
 262             {
 263                 p_sys->i_state = STATE_NEXT_SYNC;
 264             }
 265
 266             if( p_sys->i_offset )
 267             {
 268                 block_SkipBytes( &p_sys->bytestream, p_sys->i_offset );
 269                 p_sys->i_offset = 0;
 270                 block_BytestreamFlush( &p_sys->bytestream );
 271             }
 272
 273             if( p_sys->i_state != STATE_NEXT_SYNC )
 274             {
 275                 /* Need more data */
 276                 return NULL;
 277             }
 278
 279             p_sys->i_offset = 1; /* To find next startcode */
 280
 281         case STATE_NEXT_SYNC:
 282             /* TODO: If p_block == NULL, flush the buffer without checking the
 283              * next sync word */
 284
 285             /* Find the next startcode */
 286             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 287                     &p_sys->i_offset, p_sys->p_startcode, 3 ) != VLC_SUCCESS )
 288             {
 289                 /* Need more data */
 290                 return NULL;
 291             }
 292
 293             /* Get the new fragment and set the pts/dts */
 294             p_pic = block_New( p_dec, p_sys->i_offset );
 295             block_BytestreamFlush( &p_sys->bytestream );
 296             p_pic->i_pts = p_sys->bytestream.p_block->i_pts;
 297             p_pic->i_dts = p_sys->bytestream.p_block->i_dts;
 298
 299             block_GetBytes( &p_sys->bytestream, p_pic->p_buffer,
 300                             p_pic->i_buffer );
 301
 302             /* don't reuse the same timestamps several times */
 303             if( p_pic->i_buffer >= 4 && p_pic->p_buffer[3] == 0x00 )
 304             {
 305                 /* We have a picture start code */
 306                 p_sys->bytestream.p_block->i_pts = 0;
 307                 p_sys->bytestream.p_block->i_dts = 0;
 308             }
 309
 310             p_sys->i_offset = 0;
 311
 312             /* Get picture if any */
 313             if( !( p_pic = ParseMPEGBlock( p_dec, p_pic ) ) )
 314             {
 315                 p_sys->i_state = STATE_NOSYNC;
 316                 break;
 317             }
 318
 319             /* If a discontinuity has been encountered, then wait till
 320              * the next Intra frame before continuing with packetizing */
 321             if( p_sys->b_discontinuity &&
 322                 p_sys->b_sync_on_intra_frame )
 323             {
 324                 if( p_pic->i_flags & BLOCK_FLAG_TYPE_I )
 325                 {
 326                     msg_Dbg( p_dec, "synced on intra frame" );
 327                     p_sys->b_discontinuity = VLC_FALSE;
 328                     p_pic->i_flags |= BLOCK_FLAG_DISCONTINUITY;
 329                 }
 330                 else
 331                 {
 332                     msg_Dbg( p_dec, "waiting on intra frame" );
 333                     p_sys->i_state = STATE_NOSYNC;
 334                     block_Release( p_pic );
 335                     break;
 336                 }
 337             }
 338
 339             /* We've just started the stream, wait for the first PTS.
 340              * We discard here so we can still get the sequence header. */
 341             if( p_sys->i_dts <= 0 && p_sys->i_pts <= 0 &&
 342                 p_sys->i_interpolated_dts <= 0 )
 343             {
 344                 msg_Dbg( p_dec, "need a starting pts/dts" );
 345                 p_sys->i_state = STATE_NOSYNC;
 346                 block_Release( p_pic );
 347                 break;
 348             }
 349
 350             /* When starting the stream we can have the first frame with
 351              * a null DTS (i_interpolated_pts is initialized to 0) */
 352             if( !p_pic->i_dts ) p_pic->i_dts = p_pic->i_pts;
 353
 354             /* So p_block doesn't get re-added several times */
 355             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 356
 357             p_sys->i_state = STATE_NOSYNC;
 358
 359             return p_pic;
 360         }
 361     }
 362 }
 363
 364 /*****************************************************************************
 365  * ParseMPEGBlock: Re-assemble fragments into a block containing a picture
 366  *****************************************************************************/
 367 static block_t *ParseMPEGBlock( decoder_t *p_dec, block_t *p_frag )
 368 {
 369     decoder_sys_t *p_sys = p_dec->p_sys;
 370     block_t *p_pic = NULL;
 371
 372     /*
 373      * Check if previous picture is finished
 374      */
 375     if( ( p_sys->b_frame_slice &&
 376           (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) ) &&
 377           p_sys->p_seq == NULL )
 378     {
 379         /* We have a picture but without a sequence header we can't
 380          * do anything */
 381         msg_Dbg( p_dec, "waiting for sequence start" );
 382         if( p_sys->p_frame ) block_ChainRelease( p_sys->p_frame );
 383         p_sys->p_frame = NULL;
 384         p_sys->pp_last = &p_sys->p_frame;
 385         p_sys->b_frame_slice = VLC_FALSE;
 386
 387     }
 388     else if( p_sys->b_frame_slice &&
 389              (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) )
 390     {
 391         mtime_t i_duration;
 392
 393         p_pic = block_ChainGather( p_sys->p_frame );
 394
 395         i_duration = (mtime_t)( 1000000 * p_sys->i_frame_rate_base /
 396                                 p_sys->i_frame_rate );
 397
 398         if( !p_sys->b_seq_progressive && p_sys->i_picture_structure != 0x03 )
 399         {
 400             i_duration /= 2;
 401         }
 402
 403         if( p_sys->b_seq_progressive )
 404         {
 405             if( p_sys->i_top_field_first == 0 &&
 406                 p_sys->i_repeat_first_field == 1 )
 407             {
 408                 i_duration *= 2;
 409             }
 410             else if( p_sys->i_top_field_first == 1 &&
 411                      p_sys->i_repeat_first_field == 1 )
 412             {
 413                 i_duration *= 3;
 414             }
 415         }
 416         else
 417         {
 418             if( p_sys->i_picture_structure == 0x03 )
 419             {
 420                 if( p_sys->i_progressive_frame && p_sys->i_repeat_first_field )
 421                 {
 422                     i_duration += i_duration / 2;
 423                 }
 424             }
 425         }
 426
 427         if( p_sys->b_low_delay || p_sys->i_picture_type == 0x03 )
 428         {
 429             /* Trivial case (DTS == PTS) */
 430             /* Correct interpolated dts when we receive a new pts/dts */
 431             if( p_sys->i_pts > 0 ) p_sys->i_interpolated_dts = p_sys->i_pts;
 432             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 433         }
 434         else
 435         {
 436             /* Correct interpolated dts when we receive a new pts/dts */
 437             if( p_sys->i_last_ref_pts > 0 && !p_sys->b_second_field )
 438                 p_sys->i_interpolated_dts = p_sys->i_last_ref_pts;
 439             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 440
 441             if( !p_sys->b_second_field )
 442                 p_sys->i_last_ref_pts = p_sys->i_pts;
 443         }
 444
 445         p_pic->i_dts = p_sys->i_interpolated_dts;
 446         p_sys->i_interpolated_dts += i_duration;
 447
 448         /* Set PTS only if we have a B frame or if it comes from the stream */
 449         if( p_sys->i_pts > 0 )
 450         {
 451             p_pic->i_pts = p_sys->i_pts;
 452         }
 453         else if( p_sys->i_picture_type == 0x03 )
 454         {
 455             p_pic->i_pts = p_pic->i_dts;
 456         }
 457         else
 458         {
 459             p_pic->i_pts = 0;
 460         }
 461
 462         switch ( p_sys->i_picture_type )
 463         {
 464         case 0x01:
 465             p_pic->i_flags |= BLOCK_FLAG_TYPE_I;
 466             break;
 467         case 0x02:
 468             p_pic->i_flags |= BLOCK_FLAG_TYPE_P;
 469             break;
 470         case 0x03:
 471             p_pic->i_flags |= BLOCK_FLAG_TYPE_B;
 472             break;
 473         }
 474
 475         p_pic->i_length = p_sys->i_interpolated_dts - p_pic->i_dts;
 476
 477 #if 0
 478         msg_Dbg( p_dec, "pic: type=%d dts="I64Fd" pts-dts="I64Fd,
 479         p_sys->i_picture_type, p_pic->i_dts, p_pic->i_pts - p_pic->i_dts);
 480 #endif
 481
 482         /* Reset context */
 483         p_sys->p_frame = NULL;
 484         p_sys->pp_last = &p_sys->p_frame;
 485         p_sys->b_frame_slice = VLC_FALSE;
 486
 487         if( p_sys->i_picture_structure != 0x03 )
 488         {
 489             p_sys->b_second_field = !p_sys->b_second_field;
 490         }
 491         else
 492         {
 493             p_sys->b_second_field = 0;
 494         }
 495     }
 496
 497     /*
 498      * Check info of current fragment
 499      */
 500     if( p_frag->p_buffer[3] == 0xb8 )
 501     {
 502         /* Group start code */
 503         if( p_sys->p_seq &&
 504             p_sys->i_seq_old > p_sys->i_frame_rate/p_sys->i_frame_rate_base )
 505         {
 506             /* Usefull for mpeg1: repeat sequence header every second */
 507             block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_seq ) );
 508             if( p_sys->p_ext )
 509             {
 510                 block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_ext ) );
 511             }
 512
 513             p_sys->i_seq_old = 0;
 514         }
 515     }
 516     else if( p_frag->p_buffer[3] == 0xb3 && p_frag->i_buffer >= 8 )
 517     {
 518         /* Sequence header code */
 519         static const int code_to_frame_rate[16][2] =
 520         {
 521             { 1, 1 },  /* invalid */
 522             { 24000, 1001 }, { 24, 1 }, { 25, 1 },       { 30000, 1001 },
 523             { 30, 1 },       { 50, 1 }, { 60000, 1001 }, { 60, 1 },
 524             /* Unofficial 15fps from Xing*/
 525             { 15, 1001 },
 526             /* Unofficial economy rates from libmpeg3 */
 527             { 5, 1001 }, { 10, 1001 }, { 12, 1001 }, { 15, 1001 },
 528             { 1, 1 },  { 1, 1 }  /* invalid */
 529         };
 530
 531         if( p_sys->p_seq ) block_Release( p_sys->p_seq );
 532         if( p_sys->p_ext ) block_Release( p_sys->p_ext );
 533
 534         p_sys->p_seq = block_Duplicate( p_frag );
 535         p_sys->i_seq_old = 0;
 536         p_sys->p_ext = NULL;
 537
 538         p_dec->fmt_out.video.i_width =
 539             ( p_frag->p_buffer[4] << 4)|(p_frag->p_buffer[5] >> 4 );
 540         p_dec->fmt_out.video.i_height =
 541             ( (p_frag->p_buffer[5]&0x0f) << 8 )|p_frag->p_buffer[6];
 542         p_sys->i_aspect_ratio_info = p_frag->p_buffer[7] >> 4;
 543
 544         /* TODO: MPEG1 aspect ratio */
 545
 546         p_sys->i_frame_rate = code_to_frame_rate[p_frag->p_buffer[7]&0x0f][0];
 547         p_sys->i_frame_rate_base =
 548             code_to_frame_rate[p_frag->p_buffer[7]&0x0f][1];
 549
 550         p_dec->fmt_out.video.i_frame_rate = p_sys->i_frame_rate;
 551         p_dec->fmt_out.video.i_frame_rate_base = p_sys->i_frame_rate_base;
 552
 553         p_sys->b_seq_progressive = VLC_TRUE;
 554         p_sys->b_low_delay = VLC_TRUE;
 555
 556         if ( !p_sys->b_inited )
 557         {
 558             msg_Dbg( p_dec, "size %dx%d fps=%.3f",
 559                  p_dec->fmt_out.video.i_width, p_dec->fmt_out.video.i_height,
 560                  p_sys->i_frame_rate / (float)p_sys->i_frame_rate_base );
 561             p_sys->b_inited = 1;
 562         }
 563     }
 564     else if( p_frag->p_buffer[3] == 0xb5 )
 565     {
 566         int i_type = p_frag->p_buffer[4] >> 4;
 567
 568         /* Extension start code */
 569         if( i_type == 0x01 )
 570         {
 571 #if 0
 572             static const int mpeg2_aspect[16][2] =
 573             {
 574                 {0,1}, {1,1}, {4,3}, {16,9}, {221,100},
 575                 {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1},
 576                 {0,1}, {0,1}
 577             };
 578 #endif
 579
 580             /* sequence extension */
 581             if( p_sys->p_ext) block_Release( p_sys->p_ext );
 582             p_sys->p_ext = block_Duplicate( p_frag );
 583
 584             if( p_frag->i_buffer >= 10 )
 585             {
 586                 p_sys->b_seq_progressive =
 587                     p_frag->p_buffer[5]&0x08 ? VLC_TRUE : VLC_FALSE;
 588                 p_sys->b_low_delay =
 589                     p_frag->p_buffer[9]&0x80 ? VLC_TRUE : VLC_FALSE;
 590             }
 591
 592             /* Do not set aspect ratio : in case we're transcoding,
 593              * transcode will take our fmt_out as a fmt_in to libmpeg2.
 594              * libmpeg2.c will then believe that the user has requested
 595              * a specific aspect ratio, which she hasn't. Thus in case
 596              * of aspect ratio change, we're screwed. --Meuuh
 597              */
 598 #if 0
 599             p_dec->fmt_out.video.i_aspect =
 600                 mpeg2_aspect[p_sys->i_aspect_ratio_info][0] *
 601                 VOUT_ASPECT_FACTOR /
 602                 mpeg2_aspect[p_sys->i_aspect_ratio_info][1];
 603 #endif
 604
 605         }
 606         else if( i_type == 0x08 )
 607         {
 608             /* picture extension */
 609             p_sys->i_picture_structure = p_frag->p_buffer[6]&0x03;
 610             p_sys->i_top_field_first   = p_frag->p_buffer[7] >> 7;
 611             p_sys->i_repeat_first_field= (p_frag->p_buffer[7]>>1)&0x01;
 612             p_sys->i_progressive_frame = p_frag->p_buffer[8] >> 7;
 613         }
 614     }
 615     else if( p_frag->p_buffer[3] == 0x00 )
 616     {
 617         /* Picture start code */
 618         p_sys->i_seq_old++;
 619
 620         if( p_frag->i_buffer >= 6 )
 621         {
 622             p_sys->i_temporal_ref =
 623                 ( p_frag->p_buffer[4] << 2 )|(p_frag->p_buffer[5] >> 6);
 624             p_sys->i_picture_type = ( p_frag->p_buffer[5] >> 3 ) & 0x03;
 625         }
 626
 627         p_sys->i_dts = p_frag->i_dts;
 628         p_sys->i_pts = p_frag->i_pts;
 629     }
 630     else if( p_frag->p_buffer[3] >= 0x01 && p_frag->p_buffer[3] <= 0xaf )
 631     {
 632         /* Slice start code */
 633         p_sys->b_frame_slice = VLC_TRUE;
 634     }
 635
 636     /* Append the block */
 637     block_ChainLastAppend( &p_sys->pp_last, p_frag );
 638
 639     return p_pic;
 640 }