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) 2001-2005 VideoLAN (Centrale Réseaux) and its contributors
   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/decoder.h>
  48 #include <vlc/input.h>
  49
  50 #include "vlc_block_helper.h"
  51
  52 #define SYNC_INTRAFRAME_TEXT N_("Sync on intraframe")
  53 #define SYNC_INTRAFRAME_LONGTEXT N_("Normally the packetizer would " \
  54     "sync on the next full frame. This flags instructs the packetizer " \
  55     "to sync on the first intraframe found.")
  56
  57 /*****************************************************************************
  58  * Module descriptor
  59  *****************************************************************************/
  60 static int  Open ( vlc_object_t * );
  61 static void Close( vlc_object_t * );
  62
  63 vlc_module_begin();
  64     set_category( CAT_SOUT );
  65     set_subcategory( SUBCAT_SOUT_PACKETIZER );
  66     set_description( _("MPEG-I/II video packetizer") );
  67     set_capability( "packetizer", 50 );
  68     set_callbacks( Open, Close );
  69
  70     add_bool( "packetizer-mpegvideo-sync-iframe", 0, NULL, SYNC_INTRAFRAME_TEXT,
  71               SYNC_INTRAFRAME_LONGTEXT, VLC_TRUE );
  72 vlc_module_end();
  73
  74 /*****************************************************************************
  75  * Local prototypes
  76  *****************************************************************************/
  77 static block_t *Packetize( decoder_t *, block_t ** );
  78 static block_t *ParseMPEGBlock( decoder_t *, block_t * );
  79
  80 struct decoder_sys_t
  81 {
  82     /*
  83      * Input properties
  84      */
  85     block_bytestream_t bytestream;
  86     int i_state;
  87     int i_offset;
  88     uint8_t p_startcode[3];
  89
  90     /* Sequence header and extension */
  91     block_t *p_seq;
  92     block_t *p_ext;
  93
  94     /* Current frame being built */
  95     block_t    *p_frame;
  96     block_t    **pp_last;
  97
  98     vlc_bool_t b_frame_slice;
  99     mtime_t i_pts;
 100     mtime_t i_dts;
 101
 102     /* Sequence properties */
 103     int         i_frame_rate;
 104     int         i_frame_rate_base;
 105     vlc_bool_t  b_seq_progressive;
 106     vlc_bool_t  b_low_delay;
 107     int         i_aspect_ratio_info;
 108     vlc_bool_t  b_inited;
 109
 110     /* Picture properties */
 111     int i_temporal_ref;
 112     int i_picture_type;
 113     int i_picture_structure;
 114     int i_top_field_first;
 115     int i_repeat_first_field;
 116     int i_progressive_frame;
 117
 118     mtime_t i_interpolated_dts;
 119     mtime_t i_old_duration;
 120     mtime_t i_last_ref_pts;
 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
 189     p_sys->b_discontinuity = VLC_FALSE;
 190     p_sys->b_sync_on_intra_frame = var_CreateGetBool( p_dec, "packetizer-mpegvideo-sync-iframe" );
 191     if( p_sys->b_sync_on_intra_frame )
 192         msg_Dbg( p_dec, "syncing happens on intraframe now." );
 193
 194     return VLC_SUCCESS;
 195 }
 196
 197 /*****************************************************************************
 198  * Close:
 199  *****************************************************************************/
 200 static void Close( vlc_object_t *p_this )
 201 {
 202     decoder_t     *p_dec = (decoder_t*)p_this;
 203     decoder_sys_t *p_sys = p_dec->p_sys;
 204
 205     block_BytestreamRelease( &p_sys->bytestream );
 206
 207     if( p_sys->p_seq )
 208     {
 209         block_Release( p_sys->p_seq );
 210     }
 211     if( p_sys->p_ext )
 212     {
 213         block_Release( p_sys->p_ext );
 214     }
 215     if( p_sys->p_frame )
 216     {
 217         block_ChainRelease( p_sys->p_frame );
 218     }
 219
 220     var_Destroy( p_dec, "packetizer-mpegvideo-sync-iframe" );
 221
 222     free( p_sys );
 223 }
 224
 225 /*****************************************************************************
 226  * Packetize:
 227  *****************************************************************************/
 228 static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
 229 {
 230     decoder_sys_t *p_sys = p_dec->p_sys;
 231     block_t       *p_pic;
 232
 233     if( pp_block == NULL || *pp_block == NULL )
 234     {
 235         return NULL;
 236     }
 237
 238     if( (*pp_block)->i_flags & (BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 239     {
 240         p_sys->i_state = STATE_NOSYNC;
 241         p_sys->b_discontinuity = VLC_TRUE;
 242         if( p_sys->p_frame )
 243             block_ChainRelease( p_sys->p_frame );
 244         p_sys->p_frame = NULL;
 245         p_sys->pp_last = &p_sys->p_frame;
 246         p_sys->b_frame_slice = VLC_FALSE;
 247         block_Release( *pp_block );
 248         return NULL;
 249     }
 250
 251     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 252
 253     while( 1 )
 254     {
 255         switch( p_sys->i_state )
 256         {
 257
 258         case STATE_NOSYNC:
 259             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 260                     &p_sys->i_offset, p_sys->p_startcode, 3 ) == VLC_SUCCESS )
 261             {
 262                 p_sys->i_state = STATE_NEXT_SYNC;
 263             }
 264
 265             if( p_sys->i_offset )
 266             {
 267                 block_SkipBytes( &p_sys->bytestream, p_sys->i_offset );
 268                 p_sys->i_offset = 0;
 269                 block_BytestreamFlush( &p_sys->bytestream );
 270             }
 271
 272             if( p_sys->i_state != STATE_NEXT_SYNC )
 273             {
 274                 /* Need more data */
 275                 return NULL;
 276             }
 277
 278             p_sys->i_offset = 1; /* To find next startcode */
 279
 280         case STATE_NEXT_SYNC:
 281             /* TODO: If p_block == NULL, flush the buffer without checking the
 282              * next sync word */
 283
 284             /* Find the next startcode */
 285             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 286                     &p_sys->i_offset, p_sys->p_startcode, 3 ) != VLC_SUCCESS )
 287             {
 288                 /* Need more data */
 289                 return NULL;
 290             }
 291
 292             /* Get the new fragment and set the pts/dts */
 293             p_pic = block_New( p_dec, p_sys->i_offset );
 294             block_BytestreamFlush( &p_sys->bytestream );
 295             p_pic->i_pts = p_sys->bytestream.p_block->i_pts;
 296             p_pic->i_dts = p_sys->bytestream.p_block->i_dts;
 297
 298             block_GetBytes( &p_sys->bytestream, p_pic->p_buffer,
 299                             p_pic->i_buffer );
 300
 301             /* don't reuse the same timestamps several times */
 302             if( p_pic->i_buffer >= 4 && p_pic->p_buffer[3] == 0x00 )
 303             {
 304                 /* We have a picture start code */
 305                 p_sys->bytestream.p_block->i_pts = 0;
 306                 p_sys->bytestream.p_block->i_dts = 0;
 307             }
 308
 309             p_sys->i_offset = 0;
 310
 311             /* Get picture if any */
 312             if( !( p_pic = ParseMPEGBlock( p_dec, p_pic ) ) )
 313             {
 314                 p_sys->i_state = STATE_NOSYNC;
 315                 break;
 316             }
 317
 318             /* If a discontinuity has been encountered, then wait till
 319              * the next Intra frame before continuing with packetizing */
 320             if( p_sys->b_discontinuity &&
 321                 p_sys->b_sync_on_intra_frame )
 322             {
 323                 if( p_pic->i_flags & BLOCK_FLAG_TYPE_I )
 324                 {
 325                     msg_Dbg( p_dec, "synced on Intra frame" );
 326                     p_sys->b_discontinuity = VLC_FALSE;
 327                     p_pic->i_flags |= BLOCK_FLAG_DISCONTINUITY;
 328                 }
 329                 else
 330                 {
 331                     msg_Dbg( p_dec, "waiting on Intra frame" );
 332                     p_sys->i_state = STATE_NOSYNC;
 333                     block_Release( p_pic );
 334                     break;
 335                 }
 336             }
 337
 338             /* We've just started the stream, wait for the first PTS.
 339              * We discard here so we can still get the sequence header. */
 340             if( p_sys->i_dts <= 0 && p_sys->i_pts <= 0 &&
 341                 p_sys->i_interpolated_dts <= 0 )
 342             {
 343                 msg_Dbg( p_dec, "need a starting pts/dts" );
 344                 p_sys->i_state = STATE_NOSYNC;
 345                 block_Release( p_pic );
 346                 break;
 347             }
 348
 349             /* When starting the stream we can have the first frame with
 350              * a null DTS (i_interpolated_pts is initialized to 0) */
 351             if( !p_pic->i_dts ) p_pic->i_dts = p_pic->i_pts;
 352
 353             /* So p_block doesn't get re-added several times */
 354             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 355
 356             p_sys->i_state = STATE_NOSYNC;
 357
 358             return p_pic;
 359         }
 360     }
 361 }
 362
 363 /*****************************************************************************
 364  * ParseMPEGBlock: Re-assemble fragments into a block containing a picture
 365  *****************************************************************************/
 366 static block_t *ParseMPEGBlock( decoder_t *p_dec, block_t *p_frag )
 367 {
 368     decoder_sys_t *p_sys = p_dec->p_sys;
 369     block_t *p_pic = NULL;
 370
 371     /*
 372      * Check if previous picture is finished
 373      */
 374     if( ( p_sys->b_frame_slice &&
 375           (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) ) &&
 376           p_sys->p_seq == NULL )
 377     {
 378         /* We have a picture but without a sequence header we can't
 379          * do anything */
 380         msg_Dbg( p_dec, "waiting for sequence start" );
 381         if( p_sys->p_frame ) block_ChainRelease( p_sys->p_frame );
 382         p_sys->p_frame = NULL;
 383         p_sys->pp_last = &p_sys->p_frame;
 384         p_sys->b_frame_slice = VLC_FALSE;
 385
 386     }
 387     else if( p_sys->b_frame_slice &&
 388              (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) )
 389     {
 390         mtime_t i_duration;
 391
 392         p_pic = block_ChainGather( p_sys->p_frame );
 393
 394         i_duration = (mtime_t)( 1000000 * p_sys->i_frame_rate_base /
 395                                 p_sys->i_frame_rate );
 396
 397         if( !p_sys->b_seq_progressive && p_sys->i_picture_structure != 0x03 )
 398         {
 399             i_duration /= 2;
 400         }
 401
 402         if( p_sys->b_seq_progressive )
 403         {
 404             if( p_sys->i_top_field_first == 0 &&
 405                 p_sys->i_repeat_first_field == 1 )
 406             {
 407                 i_duration *= 2;
 408             }
 409             else if( p_sys->i_top_field_first == 1 &&
 410                      p_sys->i_repeat_first_field == 1 )
 411             {
 412                 i_duration *= 3;
 413             }
 414         }
 415         else
 416         {
 417             if( p_sys->i_picture_structure == 0x03 )
 418             {
 419                 if( p_sys->i_progressive_frame && p_sys->i_repeat_first_field )
 420                 {
 421                     i_duration += i_duration / 2;
 422                 }
 423             }
 424         }
 425
 426         if( p_sys->b_low_delay || p_sys->i_picture_type == 0x03 )
 427         {
 428             /* Trivial case (DTS == PTS) */
 429             /* Correct interpolated dts when we receive a new pts/dts */
 430             if( p_sys->i_pts > 0 ) p_sys->i_interpolated_dts = p_sys->i_pts;
 431             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 432         }
 433         else
 434         {
 435             /* Correct interpolated dts when we receive a new pts/dts */
 436             if( p_sys->i_last_ref_pts > 0 )
 437                 p_sys->i_interpolated_dts = p_sys->i_last_ref_pts;
 438             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 439
 440             p_sys->i_last_ref_pts = p_sys->i_pts;
 441         }
 442
 443         p_pic->i_dts = p_sys->i_interpolated_dts;
 444
 445         /* Set PTS only if we have a B frame or if it comes from the stream */
 446         if( p_sys->i_pts > 0 )
 447         {
 448             p_pic->i_pts = p_sys->i_pts;
 449         }
 450         else if( p_sys->i_picture_type == 0x03 )
 451         {
 452             p_pic->i_pts = p_pic->i_dts;
 453         }
 454         else
 455         {
 456             p_pic->i_pts = 0;
 457         }
 458
 459         if( p_sys->b_low_delay || p_sys->i_picture_type == 0x03 )
 460         {
 461             /* Trivial case (DTS == PTS) */
 462             p_sys->i_interpolated_dts += i_duration;
 463         }
 464         else
 465         {
 466             p_sys->i_interpolated_dts += p_sys->i_old_duration;
 467             p_sys->i_old_duration = i_duration;
 468         }
 469
 470         switch ( p_sys->i_picture_type )
 471         {
 472         case 0x01:
 473             p_pic->i_flags |= BLOCK_FLAG_TYPE_I;
 474             break;
 475         case 0x02:
 476             p_pic->i_flags |= BLOCK_FLAG_TYPE_P;
 477             break;
 478         case 0x03:
 479             p_pic->i_flags |= BLOCK_FLAG_TYPE_B;
 480             break;
 481         }
 482
 483         p_pic->i_length = p_sys->i_interpolated_dts - p_pic->i_dts;
 484
 485 #if 0
 486         msg_Dbg( p_dec, "pic: type=%d dts="I64Fd" pts-dts="I64Fd,
 487         p_sys->i_picture_type, p_pic->i_dts, p_pic->i_pts - p_pic->i_dts);
 488 #endif
 489
 490         /* Reset context */
 491         p_sys->p_frame = NULL;
 492         p_sys->pp_last = &p_sys->p_frame;
 493         p_sys->b_frame_slice = VLC_FALSE;
 494     }
 495
 496     /*
 497      * Check info of current fragment
 498      */
 499     if( p_frag->p_buffer[3] == 0xb8 )
 500     {
 501         /* Group start code */
 502         if( p_sys->p_seq &&
 503             p_sys->i_seq_old > p_sys->i_frame_rate/p_sys->i_frame_rate_base )
 504         {
 505             /* Usefull for mpeg1: repeat sequence header every second */
 506             block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_seq ) );
 507             if( p_sys->p_ext )
 508             {
 509                 block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_ext ) );
 510             }
 511
 512             p_sys->i_seq_old = 0;
 513         }
 514     }
 515     else if( p_frag->p_buffer[3] == 0xb3 && p_frag->i_buffer >= 8 )
 516     {
 517         /* Sequence header code */
 518         static const int code_to_frame_rate[16][2] =
 519         {
 520             { 1, 1 },  /* invalid */
 521             { 24000, 1001 }, { 24, 1 }, { 25, 1 },       { 30000, 1001 },
 522             { 30, 1 },       { 50, 1 }, { 60000, 1001 }, { 60, 1 },
 523             /* Unofficial 15fps from Xing*/
 524             { 15, 1001 },
 525             /* Unofficial economy rates from libmpeg3 */
 526             { 5, 1001 }, { 10, 1001 }, { 12, 1001 }, { 15, 1001 },
 527             { 1, 1 },  { 1, 1 }  /* invalid */
 528         };
 529
 530         if( p_sys->p_seq ) block_Release( p_sys->p_seq );
 531         if( p_sys->p_ext ) block_Release( p_sys->p_ext );
 532
 533         p_sys->p_seq = block_Duplicate( p_frag );
 534         p_sys->i_seq_old = 0;
 535         p_sys->p_ext = NULL;
 536
 537         p_dec->fmt_out.video.i_width =
 538             ( p_frag->p_buffer[4] << 4)|(p_frag->p_buffer[5] >> 4 );
 539         p_dec->fmt_out.video.i_height =
 540             ( (p_frag->p_buffer[5]&0x0f) << 8 )|p_frag->p_buffer[6];
 541         p_sys->i_aspect_ratio_info = p_frag->p_buffer[7] >> 4;
 542
 543         /* TODO: MPEG1 aspect ratio */
 544
 545         p_sys->i_frame_rate = code_to_frame_rate[p_frag->p_buffer[7]&0x0f][0];
 546         p_sys->i_frame_rate_base =
 547             code_to_frame_rate[p_frag->p_buffer[7]&0x0f][1];
 548
 549         p_dec->fmt_out.video.i_frame_rate = p_sys->i_frame_rate;
 550         p_dec->fmt_out.video.i_frame_rate_base = p_sys->i_frame_rate_base;
 551
 552         p_sys->b_seq_progressive = VLC_TRUE;
 553         p_sys->b_low_delay = VLC_TRUE;
 554
 555         if ( !p_sys->b_inited )
 556         {
 557             msg_Dbg( p_dec, "Size %dx%d fps=%.3f",
 558                  p_dec->fmt_out.video.i_width, p_dec->fmt_out.video.i_height,
 559                  p_sys->i_frame_rate / (float)p_sys->i_frame_rate_base );
 560             p_sys->b_inited = 1;
 561         }
 562     }
 563     else if( p_frag->p_buffer[3] == 0xb5 )
 564     {
 565         int i_type = p_frag->p_buffer[4] >> 4;
 566
 567         /* Extention start code */
 568         if( i_type == 0x01 )
 569         {
 570 #if 0
 571             static const int mpeg2_aspect[16][2] =
 572             {
 573                 {0,1}, {1,1}, {4,3}, {16,9}, {221,100},
 574                 {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1},
 575                 {0,1}, {0,1}
 576             };
 577 #endif
 578
 579             /* sequence extention */
 580             if( p_sys->p_ext) block_Release( p_sys->p_ext );
 581             p_sys->p_ext = block_Duplicate( p_frag );
 582
 583             if( p_frag->i_buffer >= 10 )
 584             {
 585                 p_sys->b_seq_progressive =
 586                     p_frag->p_buffer[5]&0x08 ? VLC_TRUE : VLC_FALSE;
 587                 p_sys->b_low_delay =
 588                     p_frag->p_buffer[9]&0x80 ? VLC_TRUE : VLC_FALSE;
 589             }
 590
 591             /* Do not set aspect ratio : in case we're transcoding,
 592              * transcode will take our fmt_out as a fmt_in to libmpeg2.
 593              * libmpeg2.c will then believe that the user has requested
 594              * a specific aspect ratio, which she hasn't. Thus in case
 595              * of aspect ratio change, we're screwed. --Meuuh
 596              */
 597 #if 0
 598             p_dec->fmt_out.video.i_aspect =
 599                 mpeg2_aspect[p_sys->i_aspect_ratio_info][0] *
 600                 VOUT_ASPECT_FACTOR /
 601                 mpeg2_aspect[p_sys->i_aspect_ratio_info][1];
 602 #endif
 603
 604         }
 605         else if( i_type == 0x08 )
 606         {
 607             /* picture extention */
 608             p_sys->i_picture_structure = p_frag->p_buffer[6]&0x03;
 609             p_sys->i_top_field_first   = p_frag->p_buffer[7] >> 7;
 610             p_sys->i_repeat_first_field= (p_frag->p_buffer[7]>>1)&0x01;
 611             p_sys->i_progressive_frame = p_frag->p_buffer[8] >> 7;
 612         }
 613     }
 614     else if( p_frag->p_buffer[3] == 0x00 )
 615     {
 616         /* Picture start code */
 617         p_sys->i_seq_old++;
 618
 619         if( p_frag->i_buffer >= 6 )
 620         {
 621             p_sys->i_temporal_ref =
 622                 ( p_frag->p_buffer[4] << 2 )|(p_frag->p_buffer[5] >> 6);
 623             p_sys->i_picture_type = ( p_frag->p_buffer[5] >> 3 ) & 0x03;
 624         }
 625
 626         p_sys->i_dts = p_frag->i_dts;
 627         p_sys->i_pts = p_frag->i_pts;
 628     }
 629     else if( p_frag->p_buffer[3] >= 0x01 && p_frag->p_buffer[3] <= 0xaf )
 630     {
 631         /* Slice start code */
 632         p_sys->b_frame_slice = VLC_TRUE;
 633     }
 634
 635     /* Append the block */
 636     block_ChainLastAppend( &p_sys->pp_last, p_frag );
 637
 638     return p_pic;
 639 }