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
  45 #include <vlc/vlc.h>
  46 #include <vlc_block.h>
  47 #include <vlc_codec.h>
  48 #include <vlc_block_helper.h>
  49 #include "../codec/cc.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 static block_t *GetCc( decoder_t *p_dec, vlc_bool_t pb_present[4] );
  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_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     vlc_bool_t b_cc_reset;
 131     uint32_t i_cc_flags;
 132     mtime_t i_cc_pts;
 133     mtime_t i_cc_dts;
 134     cc_data_t cc;
 135 };
 136
 137 enum {
 138     STATE_NOSYNC,
 139     STATE_NEXT_SYNC
 140 };
 141
 142 /*****************************************************************************
 143  * Open:
 144  *****************************************************************************/
 145 static int Open( vlc_object_t *p_this )
 146 {
 147     decoder_t *p_dec = (decoder_t*)p_this;
 148     decoder_sys_t *p_sys;
 149
 150     if( p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', '1' ) &&
 151         p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', '2' ) &&
 152         p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', 'v' ) )
 153     {
 154         return VLC_EGENERIC;
 155     }
 156
 157     es_format_Init( &p_dec->fmt_out, VIDEO_ES, VLC_FOURCC('m','p','g','v') );
 158     p_dec->pf_packetize = Packetize;
 159     p_dec->pf_get_cc = GetCc;
 160
 161     p_dec->p_sys = p_sys = malloc( sizeof( decoder_sys_t ) );
 162
 163     /* Misc init */
 164     p_sys->i_state = STATE_NOSYNC;
 165     p_sys->bytestream = block_BytestreamInit( p_dec );
 166     p_sys->p_startcode[0] = 0;
 167     p_sys->p_startcode[1] = 0;
 168     p_sys->p_startcode[2] = 1;
 169     p_sys->i_offset = 0;
 170
 171     p_sys->p_seq = NULL;
 172     p_sys->p_ext = NULL;
 173     p_sys->p_frame = NULL;
 174     p_sys->pp_last = &p_sys->p_frame;
 175     p_sys->b_frame_slice = VLC_FALSE;
 176
 177     p_sys->i_dts = p_sys->i_pts = 0;
 178
 179     p_sys->i_frame_rate = 1;
 180     p_sys->i_frame_rate_base = 1;
 181     p_sys->b_seq_progressive = VLC_TRUE;
 182     p_sys->b_low_delay = VLC_TRUE;
 183     p_sys->i_seq_old = 0;
 184
 185     p_sys->i_temporal_ref = 0;
 186     p_sys->i_picture_type = 0;
 187     p_sys->i_picture_structure = 0x03; /* frame */
 188     p_sys->i_top_field_first = 0;
 189     p_sys->i_repeat_first_field = 0;
 190     p_sys->i_progressive_frame = 0;
 191     p_sys->b_inited = 0;
 192
 193     p_sys->i_interpolated_dts = 0;
 194     p_sys->i_last_ref_pts = 0;
 195     p_sys->b_second_field = 0;
 196
 197     p_sys->b_discontinuity = VLC_FALSE;
 198     p_sys->b_sync_on_intra_frame = var_CreateGetBool( p_dec, "packetizer-mpegvideo-sync-iframe" );
 199     if( p_sys->b_sync_on_intra_frame )
 200         msg_Dbg( p_dec, "syncing on intra frame now" );
 201
 202     p_sys->b_cc_reset = VLC_FALSE;
 203     p_sys->i_cc_pts = 0;
 204     p_sys->i_cc_dts = 0;
 205     p_sys->i_cc_flags = 0;
 206     cc_Init( &p_sys->cc );
 207
 208     return VLC_SUCCESS;
 209 }
 210
 211 /*****************************************************************************
 212  * Close:
 213  *****************************************************************************/
 214 static void Close( vlc_object_t *p_this )
 215 {
 216     decoder_t     *p_dec = (decoder_t*)p_this;
 217     decoder_sys_t *p_sys = p_dec->p_sys;
 218
 219     block_BytestreamRelease( &p_sys->bytestream );
 220
 221     if( p_sys->p_seq )
 222     {
 223         block_Release( p_sys->p_seq );
 224     }
 225     if( p_sys->p_ext )
 226     {
 227         block_Release( p_sys->p_ext );
 228     }
 229     if( p_sys->p_frame )
 230     {
 231         block_ChainRelease( p_sys->p_frame );
 232     }
 233
 234     var_Destroy( p_dec, "packetizer-mpegvideo-sync-iframe" );
 235
 236     free( p_sys );
 237 }
 238
 239 /*****************************************************************************
 240  * Packetize:
 241  *****************************************************************************/
 242 static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
 243 {
 244     decoder_sys_t *p_sys = p_dec->p_sys;
 245     block_t       *p_pic;
 246
 247     if( pp_block == NULL || *pp_block == NULL )
 248     {
 249         return NULL;
 250     }
 251
 252     if( (*pp_block)->i_flags&(BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 253     {
 254         if( (*pp_block)->i_flags&BLOCK_FLAG_CORRUPTED )
 255         {
 256             p_sys->i_state = STATE_NOSYNC;
 257             block_BytestreamFlush( &p_sys->bytestream );
 258
 259             p_sys->b_discontinuity = VLC_TRUE;
 260             if( p_sys->p_frame )
 261                 block_ChainRelease( p_sys->p_frame );
 262             p_sys->p_frame = NULL;
 263             p_sys->pp_last = &p_sys->p_frame;
 264             p_sys->b_frame_slice = VLC_FALSE;
 265         }
 266 //        p_sys->i_interpolated_dts =
 267 //        p_sys->i_last_ref_pts = 0;
 268
 269         block_Release( *pp_block );
 270         return NULL;
 271     }
 272
 273
 274     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 275
 276     while( 1 )
 277     {
 278         switch( p_sys->i_state )
 279         {
 280
 281         case STATE_NOSYNC:
 282             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 283                     &p_sys->i_offset, p_sys->p_startcode, 3 ) == VLC_SUCCESS )
 284             {
 285                 p_sys->i_state = STATE_NEXT_SYNC;
 286             }
 287
 288             if( p_sys->i_offset )
 289             {
 290                 block_SkipBytes( &p_sys->bytestream, p_sys->i_offset );
 291                 p_sys->i_offset = 0;
 292                 block_BytestreamFlush( &p_sys->bytestream );
 293             }
 294
 295             if( p_sys->i_state != STATE_NEXT_SYNC )
 296             {
 297                 /* Need more data */
 298                 return NULL;
 299             }
 300
 301             p_sys->i_offset = 1; /* To find next startcode */
 302
 303         case STATE_NEXT_SYNC:
 304             /* TODO: If p_block == NULL, flush the buffer without checking the
 305              * next sync word */
 306
 307             /* Find the next startcode */
 308             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 309                     &p_sys->i_offset, p_sys->p_startcode, 3 ) != VLC_SUCCESS )
 310             {
 311                 /* Need more data */
 312                 return NULL;
 313             }
 314
 315             /* Get the new fragment and set the pts/dts */
 316             p_pic = block_New( p_dec, p_sys->i_offset );
 317             block_BytestreamFlush( &p_sys->bytestream );
 318             p_pic->i_pts = p_sys->bytestream.p_block->i_pts;
 319             p_pic->i_dts = p_sys->bytestream.p_block->i_dts;
 320
 321             block_GetBytes( &p_sys->bytestream, p_pic->p_buffer,
 322                             p_pic->i_buffer );
 323
 324             /* don't reuse the same timestamps several times */
 325             if( p_pic->i_buffer >= 4 && p_pic->p_buffer[3] == 0x00 )
 326             {
 327                 /* We have a picture start code */
 328                 p_sys->bytestream.p_block->i_pts = 0;
 329                 p_sys->bytestream.p_block->i_dts = 0;
 330             }
 331
 332             p_sys->i_offset = 0;
 333
 334             /* Get picture if any */
 335             if( !( p_pic = ParseMPEGBlock( p_dec, p_pic ) ) )
 336             {
 337                 p_sys->i_state = STATE_NOSYNC;
 338                 break;
 339             }
 340
 341             /* If a discontinuity has been encountered, then wait till
 342              * the next Intra frame before continuing with packetizing */
 343             if( p_sys->b_discontinuity &&
 344                 p_sys->b_sync_on_intra_frame )
 345             {
 346                 if( p_pic->i_flags & BLOCK_FLAG_TYPE_I )
 347                 {
 348                     msg_Dbg( p_dec, "synced on intra frame" );
 349                     p_sys->b_discontinuity = VLC_FALSE;
 350                     p_pic->i_flags |= BLOCK_FLAG_DISCONTINUITY;
 351                 }
 352                 else
 353                 {
 354                     msg_Dbg( p_dec, "waiting on intra frame" );
 355                     p_sys->i_state = STATE_NOSYNC;
 356                     block_Release( p_pic );
 357                     break;
 358                 }
 359             }
 360
 361             /* We've just started the stream, wait for the first PTS.
 362              * We discard here so we can still get the sequence header. */
 363             if( p_sys->i_dts <= 0 && p_sys->i_pts <= 0 &&
 364                 p_sys->i_interpolated_dts <= 0 )
 365             {
 366                 msg_Dbg( p_dec, "need a starting pts/dts" );
 367                 p_sys->i_state = STATE_NOSYNC;
 368                 block_Release( p_pic );
 369                 break;
 370             }
 371
 372             /* When starting the stream we can have the first frame with
 373              * a null DTS (i_interpolated_pts is initialized to 0) */
 374             if( !p_pic->i_dts ) p_pic->i_dts = p_pic->i_pts;
 375
 376             /* So p_block doesn't get re-added several times */
 377             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 378
 379             p_sys->i_state = STATE_NOSYNC;
 380
 381             return p_pic;
 382         }
 383     }
 384 }
 385
 386 /*****************************************************************************
 387  * GetCc:
 388  *****************************************************************************/
 389 static block_t *GetCc( decoder_t *p_dec, vlc_bool_t pb_present[4] )
 390 {
 391     decoder_sys_t *p_sys = p_dec->p_sys;
 392     block_t *p_cc;
 393     int i;
 394
 395     for( i = 0; i < 4; i++ )
 396         pb_present[i] = p_sys->cc.pb_present[i];
 397
 398     if( p_sys->cc.i_data <= 0 )
 399         return NULL;
 400
 401     p_cc = block_New( p_dec, p_sys->cc.i_data);
 402     if( p_cc )
 403     {
 404         memcpy( p_cc->p_buffer, p_sys->cc.p_data, p_sys->cc.i_data );
 405         p_cc->i_dts =
 406         p_cc->i_pts = p_sys->cc.b_reorder ? p_sys->i_cc_pts : p_sys->i_cc_dts;
 407         p_cc->i_flags = ( p_sys->cc.b_reorder  ? p_sys->i_cc_flags : BLOCK_FLAG_TYPE_P ) & ( BLOCK_FLAG_TYPE_I|BLOCK_FLAG_TYPE_P|BLOCK_FLAG_TYPE_B);
 408     }
 409     cc_Flush( &p_sys->cc );
 410     return p_cc;
 411 }
 412
 413 /*****************************************************************************
 414  * ParseMPEGBlock: Re-assemble fragments into a block containing a picture
 415  *****************************************************************************/
 416 static block_t *ParseMPEGBlock( decoder_t *p_dec, block_t *p_frag )
 417 {
 418     decoder_sys_t *p_sys = p_dec->p_sys;
 419     block_t *p_pic = NULL;
 420
 421     /*
 422      * Check if previous picture is finished
 423      */
 424     if( ( p_sys->b_frame_slice &&
 425           (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) ) &&
 426           p_sys->p_seq == NULL )
 427     {
 428         /* We have a picture but without a sequence header we can't
 429          * do anything */
 430         msg_Dbg( p_dec, "waiting for sequence start" );
 431         if( p_sys->p_frame ) block_ChainRelease( p_sys->p_frame );
 432         p_sys->p_frame = NULL;
 433         p_sys->pp_last = &p_sys->p_frame;
 434         p_sys->b_frame_slice = VLC_FALSE;
 435
 436     }
 437     else if( p_sys->b_frame_slice &&
 438              (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) )
 439     {
 440         mtime_t i_duration;
 441
 442         p_pic = block_ChainGather( p_sys->p_frame );
 443
 444         i_duration = (mtime_t)( 1000000 * p_sys->i_frame_rate_base /
 445                                 p_sys->i_frame_rate );
 446
 447         if( !p_sys->b_seq_progressive && p_sys->i_picture_structure != 0x03 )
 448         {
 449             i_duration /= 2;
 450         }
 451
 452         if( p_sys->b_seq_progressive )
 453         {
 454             if( p_sys->i_top_field_first == 0 &&
 455                 p_sys->i_repeat_first_field == 1 )
 456             {
 457                 i_duration *= 2;
 458             }
 459             else if( p_sys->i_top_field_first == 1 &&
 460                      p_sys->i_repeat_first_field == 1 )
 461             {
 462                 i_duration *= 3;
 463             }
 464         }
 465         else
 466         {
 467             if( p_sys->i_picture_structure == 0x03 )
 468             {
 469                 if( p_sys->i_progressive_frame && p_sys->i_repeat_first_field )
 470                 {
 471                     i_duration += i_duration / 2;
 472                 }
 473             }
 474         }
 475
 476         if( p_sys->b_low_delay || p_sys->i_picture_type == 0x03 )
 477         {
 478             /* Trivial case (DTS == PTS) */
 479             /* Correct interpolated dts when we receive a new pts/dts */
 480             if( p_sys->i_pts > 0 ) p_sys->i_interpolated_dts = p_sys->i_pts;
 481             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 482         }
 483         else
 484         {
 485             /* Correct interpolated dts when we receive a new pts/dts */
 486             if( p_sys->i_last_ref_pts > 0 && !p_sys->b_second_field )
 487                 p_sys->i_interpolated_dts = p_sys->i_last_ref_pts;
 488             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 489
 490             if( !p_sys->b_second_field )
 491                 p_sys->i_last_ref_pts = p_sys->i_pts;
 492         }
 493
 494         p_pic->i_dts = p_sys->i_interpolated_dts;
 495         p_sys->i_interpolated_dts += i_duration;
 496
 497         /* Set PTS only if we have a B frame or if it comes from the stream */
 498         if( p_sys->i_pts > 0 )
 499         {
 500             p_pic->i_pts = p_sys->i_pts;
 501         }
 502         else if( p_sys->i_picture_type == 0x03 )
 503         {
 504             p_pic->i_pts = p_pic->i_dts;
 505         }
 506         else
 507         {
 508             p_pic->i_pts = 0;
 509         }
 510
 511         switch ( p_sys->i_picture_type )
 512         {
 513         case 0x01:
 514             p_pic->i_flags |= BLOCK_FLAG_TYPE_I;
 515             break;
 516         case 0x02:
 517             p_pic->i_flags |= BLOCK_FLAG_TYPE_P;
 518             break;
 519         case 0x03:
 520             p_pic->i_flags |= BLOCK_FLAG_TYPE_B;
 521             break;
 522         }
 523
 524         p_pic->i_length = p_sys->i_interpolated_dts - p_pic->i_dts;
 525
 526 #if 0
 527         msg_Dbg( p_dec, "pic: type=%d dts="I64Fd" pts-dts="I64Fd,
 528         p_sys->i_picture_type, p_pic->i_dts, p_pic->i_pts - p_pic->i_dts);
 529 #endif
 530
 531         /* Reset context */
 532         p_sys->p_frame = NULL;
 533         p_sys->pp_last = &p_sys->p_frame;
 534         p_sys->b_frame_slice = VLC_FALSE;
 535
 536         if( p_sys->i_picture_structure != 0x03 )
 537         {
 538             p_sys->b_second_field = !p_sys->b_second_field;
 539         }
 540         else
 541         {
 542             p_sys->b_second_field = 0;
 543         }
 544
 545         /* CC */
 546         p_sys->b_cc_reset = VLC_TRUE;
 547         p_sys->i_cc_pts = p_pic->i_pts;
 548         p_sys->i_cc_dts = p_pic->i_dts;
 549         p_sys->i_cc_flags = p_pic->i_flags;
 550     }
 551
 552     if( !p_pic && p_sys->b_cc_reset )
 553     {
 554         p_sys->b_cc_reset = VLC_FALSE;
 555         cc_Flush( &p_sys->cc );
 556     }
 557
 558     /*
 559      * Check info of current fragment
 560      */
 561     if( p_frag->p_buffer[3] == 0xb8 )
 562     {
 563         /* Group start code */
 564         if( p_sys->p_seq &&
 565             p_sys->i_seq_old > p_sys->i_frame_rate/p_sys->i_frame_rate_base )
 566         {
 567             /* Usefull for mpeg1: repeat sequence header every second */
 568             block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_seq ) );
 569             if( p_sys->p_ext )
 570             {
 571                 block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_ext ) );
 572             }
 573
 574             p_sys->i_seq_old = 0;
 575         }
 576     }
 577     else if( p_frag->p_buffer[3] == 0xb3 && p_frag->i_buffer >= 8 )
 578     {
 579         /* Sequence header code */
 580         static const int code_to_frame_rate[16][2] =
 581         {
 582             { 1, 1 },  /* invalid */
 583             { 24000, 1001 }, { 24, 1 }, { 25, 1 },       { 30000, 1001 },
 584             { 30, 1 },       { 50, 1 }, { 60000, 1001 }, { 60, 1 },
 585             /* Unofficial 15fps from Xing*/
 586             { 15, 1001 },
 587             /* Unofficial economy rates from libmpeg3 */
 588             { 5, 1001 }, { 10, 1001 }, { 12, 1001 }, { 15, 1001 },
 589             { 1, 1 },  { 1, 1 }  /* invalid */
 590         };
 591
 592         if( p_sys->p_seq ) block_Release( p_sys->p_seq );
 593         if( p_sys->p_ext ) block_Release( p_sys->p_ext );
 594
 595         p_sys->p_seq = block_Duplicate( p_frag );
 596         p_sys->i_seq_old = 0;
 597         p_sys->p_ext = NULL;
 598
 599         p_dec->fmt_out.video.i_width =
 600             ( p_frag->p_buffer[4] << 4)|(p_frag->p_buffer[5] >> 4 );
 601         p_dec->fmt_out.video.i_height =
 602             ( (p_frag->p_buffer[5]&0x0f) << 8 )|p_frag->p_buffer[6];
 603         p_sys->i_aspect_ratio_info = p_frag->p_buffer[7] >> 4;
 604
 605         /* TODO: MPEG1 aspect ratio */
 606
 607         p_sys->i_frame_rate = code_to_frame_rate[p_frag->p_buffer[7]&0x0f][0];
 608         p_sys->i_frame_rate_base =
 609             code_to_frame_rate[p_frag->p_buffer[7]&0x0f][1];
 610
 611         p_dec->fmt_out.video.i_frame_rate = p_sys->i_frame_rate;
 612         p_dec->fmt_out.video.i_frame_rate_base = p_sys->i_frame_rate_base;
 613
 614         p_sys->b_seq_progressive = VLC_TRUE;
 615         p_sys->b_low_delay = VLC_TRUE;
 616
 617         if ( !p_sys->b_inited )
 618         {
 619             msg_Dbg( p_dec, "size %dx%d fps=%.3f",
 620                  p_dec->fmt_out.video.i_width, p_dec->fmt_out.video.i_height,
 621                  p_sys->i_frame_rate / (float)p_sys->i_frame_rate_base );
 622             p_sys->b_inited = 1;
 623         }
 624     }
 625     else if( p_frag->p_buffer[3] == 0xb5 )
 626     {
 627         int i_type = p_frag->p_buffer[4] >> 4;
 628
 629         /* Extension start code */
 630         if( i_type == 0x01 )
 631         {
 632 #if 0
 633             static const int mpeg2_aspect[16][2] =
 634             {
 635                 {0,1}, {1,1}, {4,3}, {16,9}, {221,100},
 636                 {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1},
 637                 {0,1}, {0,1}
 638             };
 639 #endif
 640
 641             /* sequence extension */
 642             if( p_sys->p_ext) block_Release( p_sys->p_ext );
 643             p_sys->p_ext = block_Duplicate( p_frag );
 644
 645             if( p_frag->i_buffer >= 10 )
 646             {
 647                 p_sys->b_seq_progressive =
 648                     p_frag->p_buffer[5]&0x08 ? VLC_TRUE : VLC_FALSE;
 649                 p_sys->b_low_delay =
 650                     p_frag->p_buffer[9]&0x80 ? VLC_TRUE : VLC_FALSE;
 651             }
 652
 653             /* Do not set aspect ratio : in case we're transcoding,
 654              * transcode will take our fmt_out as a fmt_in to libmpeg2.
 655              * libmpeg2.c will then believe that the user has requested
 656              * a specific aspect ratio, which she hasn't. Thus in case
 657              * of aspect ratio change, we're screwed. --Meuuh
 658              */
 659 #if 0
 660             p_dec->fmt_out.video.i_aspect =
 661                 mpeg2_aspect[p_sys->i_aspect_ratio_info][0] *
 662                 VOUT_ASPECT_FACTOR /
 663                 mpeg2_aspect[p_sys->i_aspect_ratio_info][1];
 664 #endif
 665
 666         }
 667         else if( i_type == 0x08 )
 668         {
 669             /* picture extension */
 670             p_sys->i_picture_structure = p_frag->p_buffer[6]&0x03;
 671             p_sys->i_top_field_first   = p_frag->p_buffer[7] >> 7;
 672             p_sys->i_repeat_first_field= (p_frag->p_buffer[7]>>1)&0x01;
 673             p_sys->i_progressive_frame = p_frag->p_buffer[8] >> 7;
 674         }
 675     }
 676     else if( p_frag->p_buffer[3] == 0xb2 && p_frag->i_buffer > 4 )
 677     {
 678         cc_Extract( &p_sys->cc, &p_frag->p_buffer[4], p_frag->i_buffer - 4 );
 679     }
 680     else if( p_frag->p_buffer[3] == 0x00 )
 681     {
 682         /* Picture start code */
 683         p_sys->i_seq_old++;
 684
 685         if( p_frag->i_buffer >= 6 )
 686         {
 687             p_sys->i_temporal_ref =
 688                 ( p_frag->p_buffer[4] << 2 )|(p_frag->p_buffer[5] >> 6);
 689             p_sys->i_picture_type = ( p_frag->p_buffer[5] >> 3 ) & 0x03;
 690         }
 691
 692         p_sys->i_dts = p_frag->i_dts;
 693         p_sys->i_pts = p_frag->i_pts;
 694     }
 695     else if( p_frag->p_buffer[3] >= 0x01 && p_frag->p_buffer[3] <= 0xaf )
 696     {
 697         /* Slice start code */
 698         p_sys->b_frame_slice = VLC_TRUE;
 699     }
 700
 701     /* Append the block */
 702     block_ChainLastAppend( &p_sys->pp_last, p_frag );
 703
 704     return p_pic;
 705 }