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 #ifdef HAVE_CONFIG_H
  46 # include "config.h"
  47 #endif
  48
  49 #include <vlc_common.h>
  50 #include <vlc_plugin.h>
  51 #include <vlc_block.h>
  52 #include <vlc_codec.h>
  53 #include <vlc_block_helper.h>
  54 #include "../codec/cc.h"
  55
  56 #define SYNC_INTRAFRAME_TEXT N_("Sync on Intra Frame")
  57 #define SYNC_INTRAFRAME_LONGTEXT N_("Normally the packetizer would " \
  58     "sync on the next full frame. This flags instructs the packetizer " \
  59     "to sync on the first Intra Frame found.")
  60
  61 /*****************************************************************************
  62  * Module descriptor
  63  *****************************************************************************/
  64 static int  Open ( vlc_object_t * );
  65 static void Close( vlc_object_t * );
  66
  67 vlc_module_begin ()
  68     set_category( CAT_SOUT )
  69     set_subcategory( SUBCAT_SOUT_PACKETIZER )
  70     set_description( N_("MPEG-I/II video packetizer") )
  71     set_shortname( N_("MPEG Video") )
  72     set_capability( "packetizer", 50 )
  73     set_callbacks( Open, Close )
  74
  75     add_bool( "packetizer-mpegvideo-sync-iframe", 0, NULL, SYNC_INTRAFRAME_TEXT,
  76               SYNC_INTRAFRAME_LONGTEXT, true )
  77 vlc_module_end ()
  78
  79 /*****************************************************************************
  80  * Local prototypes
  81  *****************************************************************************/
  82 static block_t *Packetize( decoder_t *, block_t ** );
  83 static block_t *ParseMPEGBlock( decoder_t *, block_t * );
  84 static block_t *GetCc( decoder_t *p_dec, bool pb_present[4] );
  85
  86 struct decoder_sys_t
  87 {
  88     /*
  89      * Input properties
  90      */
  91     block_bytestream_t bytestream;
  92     int i_state;
  93     size_t i_offset;
  94     uint8_t p_startcode[3];
  95
  96     /* Sequence header and extension */
  97     block_t *p_seq;
  98     block_t *p_ext;
  99
 100     /* Current frame being built */
 101     block_t    *p_frame;
 102     block_t    **pp_last;
 103
 104     bool b_frame_slice;
 105     mtime_t i_pts;
 106     mtime_t i_dts;
 107
 108     /* Sequence properties */
 109     int         i_frame_rate;
 110     int         i_frame_rate_base;
 111     bool  b_seq_progressive;
 112     bool  b_low_delay;
 113     int         i_aspect_ratio_info;
 114     bool  b_inited;
 115
 116     /* Picture properties */
 117     int i_temporal_ref;
 118     int i_picture_type;
 119     int i_picture_structure;
 120     int i_top_field_first;
 121     int i_repeat_first_field;
 122     int i_progressive_frame;
 123
 124     mtime_t i_interpolated_dts;
 125     mtime_t i_last_ref_pts;
 126     bool b_second_field;
 127
 128     /* Number of pictures since last sequence header */
 129     int i_seq_old;
 130
 131     /* Sync behaviour */
 132     bool  b_sync_on_intra_frame;
 133     bool  b_discontinuity;
 134
 135     /* */
 136     bool b_cc_reset;
 137     uint32_t i_cc_flags;
 138     mtime_t i_cc_pts;
 139     mtime_t i_cc_dts;
 140     cc_data_t cc;
 141 };
 142
 143 enum {
 144     STATE_NOSYNC,
 145     STATE_NEXT_SYNC
 146 };
 147
 148 /*****************************************************************************
 149  * Open:
 150  *****************************************************************************/
 151 static int Open( vlc_object_t *p_this )
 152 {
 153     decoder_t *p_dec = (decoder_t*)p_this;
 154     decoder_sys_t *p_sys;
 155
 156     if( p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', '1' ) &&
 157         p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', '2' ) &&
 158         p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', 'v' ) )
 159     {
 160         return VLC_EGENERIC;
 161     }
 162
 163     es_format_Init( &p_dec->fmt_out, VIDEO_ES, VLC_FOURCC('m','p','g','v') );
 164     p_dec->pf_packetize = Packetize;
 165     p_dec->pf_get_cc = GetCc;
 166
 167     p_dec->p_sys = p_sys = malloc( sizeof( decoder_sys_t ) );
 168     if( !p_dec->p_sys )
 169         return VLC_ENOMEM;
 170     memset( p_dec->p_sys, 0, sizeof( decoder_sys_t ) );
 171
 172     /* Misc init */
 173     p_sys->i_state = STATE_NOSYNC;
 174     p_sys->bytestream = block_BytestreamInit();
 175     p_sys->p_startcode[0] = 0;
 176     p_sys->p_startcode[1] = 0;
 177     p_sys->p_startcode[2] = 1;
 178     p_sys->i_offset = 0;
 179
 180     p_sys->p_seq = NULL;
 181     p_sys->p_ext = NULL;
 182     p_sys->p_frame = NULL;
 183     p_sys->pp_last = &p_sys->p_frame;
 184     p_sys->b_frame_slice = false;
 185
 186     p_sys->i_dts = p_sys->i_pts = 0;
 187
 188     p_sys->i_frame_rate = 1;
 189     p_sys->i_frame_rate_base = 1;
 190     p_sys->b_seq_progressive = true;
 191     p_sys->b_low_delay = true;
 192     p_sys->i_seq_old = 0;
 193
 194     p_sys->i_temporal_ref = 0;
 195     p_sys->i_picture_type = 0;
 196     p_sys->i_picture_structure = 0x03; /* frame */
 197     p_sys->i_top_field_first = 0;
 198     p_sys->i_repeat_first_field = 0;
 199     p_sys->i_progressive_frame = 0;
 200     p_sys->b_inited = 0;
 201
 202     p_sys->i_interpolated_dts = 0;
 203     p_sys->i_last_ref_pts = 0;
 204     p_sys->b_second_field = 0;
 205
 206     p_sys->b_discontinuity = false;
 207     p_sys->b_sync_on_intra_frame = var_CreateGetBool( p_dec, "packetizer-mpegvideo-sync-iframe" );
 208     if( p_sys->b_sync_on_intra_frame )
 209         msg_Dbg( p_dec, "syncing on intra frame now" );
 210
 211     p_sys->b_cc_reset = false;
 212     p_sys->i_cc_pts = 0;
 213     p_sys->i_cc_dts = 0;
 214     p_sys->i_cc_flags = 0;
 215     cc_Init( &p_sys->cc );
 216
 217     return VLC_SUCCESS;
 218 }
 219
 220 /*****************************************************************************
 221  * Close:
 222  *****************************************************************************/
 223 static void Close( vlc_object_t *p_this )
 224 {
 225     decoder_t     *p_dec = (decoder_t*)p_this;
 226     decoder_sys_t *p_sys = p_dec->p_sys;
 227
 228     block_BytestreamRelease( &p_sys->bytestream );
 229
 230     if( p_sys->p_seq )
 231     {
 232         block_Release( p_sys->p_seq );
 233     }
 234     if( p_sys->p_ext )
 235     {
 236         block_Release( p_sys->p_ext );
 237     }
 238     if( p_sys->p_frame )
 239     {
 240         block_ChainRelease( p_sys->p_frame );
 241     }
 242
 243     var_Destroy( p_dec, "packetizer-mpegvideo-sync-iframe" );
 244
 245     free( p_sys );
 246 }
 247
 248 /*****************************************************************************
 249  * Packetize:
 250  *****************************************************************************/
 251 static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
 252 {
 253     decoder_sys_t *p_sys = p_dec->p_sys;
 254     block_t       *p_pic;
 255
 256     if( pp_block == NULL || *pp_block == NULL )
 257     {
 258         return NULL;
 259     }
 260
 261     if( (*pp_block)->i_flags&(BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 262     {
 263         if( (*pp_block)->i_flags&BLOCK_FLAG_CORRUPTED )
 264         {
 265             p_sys->i_state = STATE_NOSYNC;
 266             block_BytestreamEmpty( &p_sys->bytestream );
 267
 268             p_sys->b_discontinuity = true;
 269             if( p_sys->p_frame )
 270                 block_ChainRelease( p_sys->p_frame );
 271             p_sys->p_frame = NULL;
 272             p_sys->pp_last = &p_sys->p_frame;
 273             p_sys->b_frame_slice = false;
 274         }
 275         p_sys->i_dts = 0;
 276         p_sys->i_pts = 0;
 277         p_sys->i_interpolated_dts = 0;
 278         p_sys->i_last_ref_pts = 0;
 279
 280         block_Release( *pp_block );
 281         return NULL;
 282     }
 283
 284
 285     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 286
 287     while( 1 )
 288     {
 289         switch( p_sys->i_state )
 290         {
 291
 292         case STATE_NOSYNC:
 293             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 294                     &p_sys->i_offset, p_sys->p_startcode, 3 ) == VLC_SUCCESS )
 295             {
 296                 p_sys->i_state = STATE_NEXT_SYNC;
 297             }
 298
 299             if( p_sys->i_offset )
 300             {
 301                 block_SkipBytes( &p_sys->bytestream, p_sys->i_offset );
 302                 p_sys->i_offset = 0;
 303                 block_BytestreamFlush( &p_sys->bytestream );
 304             }
 305
 306             if( p_sys->i_state != STATE_NEXT_SYNC )
 307             {
 308                 /* Need more data */
 309                 return NULL;
 310             }
 311
 312             p_sys->i_offset = 1; /* To find next startcode */
 313
 314         case STATE_NEXT_SYNC:
 315             /* TODO: If p_block == NULL, flush the buffer without checking the
 316              * next sync word */
 317
 318             /* Find the next startcode */
 319             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 320                     &p_sys->i_offset, p_sys->p_startcode, 3 ) != VLC_SUCCESS )
 321             {
 322                 /* Need more data */
 323                 return NULL;
 324             }
 325
 326             /* Get the new fragment and set the pts/dts */
 327             p_pic = block_New( p_dec, p_sys->i_offset );
 328             block_BytestreamFlush( &p_sys->bytestream );
 329             p_pic->i_pts = p_sys->bytestream.p_block->i_pts;
 330             p_pic->i_dts = p_sys->bytestream.p_block->i_dts;
 331
 332             block_GetBytes( &p_sys->bytestream, p_pic->p_buffer,
 333                             p_pic->i_buffer );
 334
 335             /* don't reuse the same timestamps several times */
 336             if( p_pic->i_buffer >= 4 && p_pic->p_buffer[3] == 0x00 )
 337             {
 338                 /* We have a picture start code */
 339                 p_sys->bytestream.p_block->i_pts = 0;
 340                 p_sys->bytestream.p_block->i_dts = 0;
 341             }
 342
 343             p_sys->i_offset = 0;
 344
 345             /* Get picture if any */
 346             if( !( p_pic = ParseMPEGBlock( p_dec, p_pic ) ) )
 347             {
 348                 p_sys->i_state = STATE_NOSYNC;
 349                 break;
 350             }
 351
 352             /* If a discontinuity has been encountered, then wait till
 353              * the next Intra frame before continuing with packetizing */
 354             if( p_sys->b_discontinuity &&
 355                 p_sys->b_sync_on_intra_frame )
 356             {
 357                 if( p_pic->i_flags & BLOCK_FLAG_TYPE_I )
 358                 {
 359                     msg_Dbg( p_dec, "synced on intra frame" );
 360                     p_sys->b_discontinuity = false;
 361                     p_pic->i_flags |= BLOCK_FLAG_DISCONTINUITY;
 362                 }
 363                 else
 364                 {
 365                     msg_Dbg( p_dec, "waiting on intra frame" );
 366                     p_sys->i_state = STATE_NOSYNC;
 367                     block_Release( p_pic );
 368                     break;
 369                 }
 370             }
 371
 372             /* We've just started the stream, wait for the first PTS.
 373              * We discard here so we can still get the sequence header. */
 374             if( p_sys->i_dts <= 0 && p_sys->i_pts <= 0 &&
 375                 p_sys->i_interpolated_dts <= 0 )
 376             {
 377                 msg_Dbg( p_dec, "need a starting pts/dts" );
 378                 p_sys->i_state = STATE_NOSYNC;
 379                 block_Release( p_pic );
 380                 break;
 381             }
 382
 383             /* When starting the stream we can have the first frame with
 384              * a null DTS (i_interpolated_pts is initialized to 0) */
 385             if( !p_pic->i_dts ) p_pic->i_dts = p_pic->i_pts;
 386
 387             /* So p_block doesn't get re-added several times */
 388             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 389
 390             p_sys->i_state = STATE_NOSYNC;
 391
 392             return p_pic;
 393         }
 394     }
 395 }
 396
 397 /*****************************************************************************
 398  * GetCc:
 399  *****************************************************************************/
 400 static block_t *GetCc( decoder_t *p_dec, bool pb_present[4] )
 401 {
 402     decoder_sys_t *p_sys = p_dec->p_sys;
 403     block_t *p_cc;
 404     int i;
 405
 406     for( i = 0; i < 4; i++ )
 407         pb_present[i] = p_sys->cc.pb_present[i];
 408
 409     if( p_sys->cc.i_data <= 0 )
 410         return NULL;
 411
 412     p_cc = block_New( p_dec, p_sys->cc.i_data);
 413     if( p_cc )
 414     {
 415         memcpy( p_cc->p_buffer, p_sys->cc.p_data, p_sys->cc.i_data );
 416         p_cc->i_dts =
 417         p_cc->i_pts = p_sys->cc.b_reorder ? p_sys->i_cc_pts : p_sys->i_cc_dts;
 418         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);
 419     }
 420     cc_Flush( &p_sys->cc );
 421     return p_cc;
 422 }
 423
 424 /*****************************************************************************
 425  * ParseMPEGBlock: Re-assemble fragments into a block containing a picture
 426  *****************************************************************************/
 427 static block_t *ParseMPEGBlock( decoder_t *p_dec, block_t *p_frag )
 428 {
 429     decoder_sys_t *p_sys = p_dec->p_sys;
 430     block_t *p_pic = NULL;
 431
 432     /*
 433      * Check if previous picture is finished
 434      */
 435     if( ( p_sys->b_frame_slice &&
 436           (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) ) &&
 437           p_sys->p_seq == NULL )
 438     {
 439         /* We have a picture but without a sequence header we can't
 440          * do anything */
 441         msg_Dbg( p_dec, "waiting for sequence start" );
 442         if( p_sys->p_frame ) block_ChainRelease( p_sys->p_frame );
 443         p_sys->p_frame = NULL;
 444         p_sys->pp_last = &p_sys->p_frame;
 445         p_sys->b_frame_slice = false;
 446
 447     }
 448     else if( p_sys->b_frame_slice &&
 449              (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) )
 450     {
 451         const bool b_eos = p_frag->p_buffer[3] == 0xb7;
 452
 453         mtime_t i_duration;
 454
 455         if( b_eos )
 456         {
 457             block_ChainLastAppend( &p_sys->pp_last, p_frag );
 458             p_frag = NULL;
 459         }
 460
 461         p_pic = block_ChainGather( p_sys->p_frame );
 462
 463         if( b_eos )
 464             p_pic->i_flags |= BLOCK_FLAG_END_OF_SEQUENCE;
 465
 466         i_duration = (mtime_t)( 1000000 * p_sys->i_frame_rate_base /
 467                                 p_sys->i_frame_rate );
 468
 469         if( !p_sys->b_seq_progressive && p_sys->i_picture_structure != 0x03 )
 470         {
 471             i_duration /= 2;
 472         }
 473
 474         if( p_sys->b_seq_progressive )
 475         {
 476             if( p_sys->i_top_field_first == 0 &&
 477                 p_sys->i_repeat_first_field == 1 )
 478             {
 479                 i_duration *= 2;
 480             }
 481             else if( p_sys->i_top_field_first == 1 &&
 482                      p_sys->i_repeat_first_field == 1 )
 483             {
 484                 i_duration *= 3;
 485             }
 486         }
 487         else
 488         {
 489             if( p_sys->i_picture_structure == 0x03 )
 490             {
 491                 if( p_sys->i_progressive_frame && p_sys->i_repeat_first_field )
 492                 {
 493                     i_duration += i_duration / 2;
 494                 }
 495             }
 496         }
 497
 498         if( p_sys->b_low_delay || p_sys->i_picture_type == 0x03 )
 499         {
 500             /* Trivial case (DTS == PTS) */
 501             /* Correct interpolated dts when we receive a new pts/dts */
 502             if( p_sys->i_pts > 0 ) p_sys->i_interpolated_dts = p_sys->i_pts;
 503             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 504         }
 505         else
 506         {
 507             /* Correct interpolated dts when we receive a new pts/dts */
 508             if( p_sys->i_last_ref_pts > 0 && !p_sys->b_second_field )
 509                 p_sys->i_interpolated_dts = p_sys->i_last_ref_pts;
 510             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 511
 512             if( !p_sys->b_second_field )
 513                 p_sys->i_last_ref_pts = p_sys->i_pts;
 514         }
 515
 516         p_pic->i_dts = p_sys->i_interpolated_dts;
 517         p_sys->i_interpolated_dts += i_duration;
 518
 519         /* Set PTS only if we have a B frame or if it comes from the stream */
 520         if( p_sys->i_pts > 0 )
 521         {
 522             p_pic->i_pts = p_sys->i_pts;
 523         }
 524         else if( p_sys->i_picture_type == 0x03 )
 525         {
 526             p_pic->i_pts = p_pic->i_dts;
 527         }
 528         else
 529         {
 530             p_pic->i_pts = 0;
 531         }
 532
 533         switch ( p_sys->i_picture_type )
 534         {
 535         case 0x01:
 536             p_pic->i_flags |= BLOCK_FLAG_TYPE_I;
 537             break;
 538         case 0x02:
 539             p_pic->i_flags |= BLOCK_FLAG_TYPE_P;
 540             break;
 541         case 0x03:
 542             p_pic->i_flags |= BLOCK_FLAG_TYPE_B;
 543             break;
 544         }
 545
 546         p_pic->i_length = p_sys->i_interpolated_dts - p_pic->i_dts;
 547
 548 #if 0
 549         msg_Dbg( p_dec, "pic: type=%d dts=%"PRId64" pts-dts=%"PRId64,
 550         p_sys->i_picture_type, p_pic->i_dts, p_pic->i_pts - p_pic->i_dts);
 551 #endif
 552
 553         /* Reset context */
 554         p_sys->p_frame = NULL;
 555         p_sys->pp_last = &p_sys->p_frame;
 556         p_sys->b_frame_slice = false;
 557
 558         if( p_sys->i_picture_structure != 0x03 )
 559         {
 560             p_sys->b_second_field = !p_sys->b_second_field;
 561         }
 562         else
 563         {
 564             p_sys->b_second_field = 0;
 565         }
 566
 567         /* CC */
 568         p_sys->b_cc_reset = true;
 569         p_sys->i_cc_pts = p_pic->i_pts;
 570         p_sys->i_cc_dts = p_pic->i_dts;
 571         p_sys->i_cc_flags = p_pic->i_flags;
 572     }
 573
 574     if( !p_pic && p_sys->b_cc_reset )
 575     {
 576         p_sys->b_cc_reset = false;
 577         cc_Flush( &p_sys->cc );
 578     }
 579
 580     if( !p_frag )
 581         return p_pic;
 582     /*
 583      * Check info of current fragment
 584      */
 585     if( p_frag->p_buffer[3] == 0xb8 )
 586     {
 587         /* Group start code */
 588         if( p_sys->p_seq &&
 589             p_sys->i_seq_old > p_sys->i_frame_rate/p_sys->i_frame_rate_base )
 590         {
 591             /* Usefull for mpeg1: repeat sequence header every second */
 592             block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_seq ) );
 593             if( p_sys->p_ext )
 594             {
 595                 block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_ext ) );
 596             }
 597
 598             p_sys->i_seq_old = 0;
 599         }
 600     }
 601     else if( p_frag->p_buffer[3] == 0xb3 && p_frag->i_buffer >= 8 )
 602     {
 603         /* Sequence header code */
 604         static const int code_to_frame_rate[16][2] =
 605         {
 606             { 1, 1 },  /* invalid */
 607             { 24000, 1001 }, { 24, 1 }, { 25, 1 },       { 30000, 1001 },
 608             { 30, 1 },       { 50, 1 }, { 60000, 1001 }, { 60, 1 },
 609             /* Unofficial 15fps from Xing*/
 610             { 15, 1001 },
 611             /* Unofficial economy rates from libmpeg3 */
 612             { 5, 1001 }, { 10, 1001 }, { 12, 1001 }, { 15, 1001 },
 613             { 1, 1 },  { 1, 1 }  /* invalid */
 614         };
 615
 616         if( p_sys->p_seq ) block_Release( p_sys->p_seq );
 617         if( p_sys->p_ext ) block_Release( p_sys->p_ext );
 618
 619         p_sys->p_seq = block_Duplicate( p_frag );
 620         p_sys->i_seq_old = 0;
 621         p_sys->p_ext = NULL;
 622
 623         p_dec->fmt_out.video.i_width =
 624             ( p_frag->p_buffer[4] << 4)|(p_frag->p_buffer[5] >> 4 );
 625         p_dec->fmt_out.video.i_height =
 626             ( (p_frag->p_buffer[5]&0x0f) << 8 )|p_frag->p_buffer[6];
 627         p_sys->i_aspect_ratio_info = p_frag->p_buffer[7] >> 4;
 628
 629         /* TODO: MPEG1 aspect ratio */
 630
 631         p_sys->i_frame_rate = code_to_frame_rate[p_frag->p_buffer[7]&0x0f][0];
 632         p_sys->i_frame_rate_base =
 633             code_to_frame_rate[p_frag->p_buffer[7]&0x0f][1];
 634
 635         p_dec->fmt_out.video.i_frame_rate = p_sys->i_frame_rate;
 636         p_dec->fmt_out.video.i_frame_rate_base = p_sys->i_frame_rate_base;
 637
 638         p_sys->b_seq_progressive = true;
 639         p_sys->b_low_delay = true;
 640
 641         if ( !p_sys->b_inited )
 642         {
 643             msg_Dbg( p_dec, "size %dx%d fps=%.3f",
 644                  p_dec->fmt_out.video.i_width, p_dec->fmt_out.video.i_height,
 645                  p_sys->i_frame_rate / (float)p_sys->i_frame_rate_base );
 646             p_sys->b_inited = 1;
 647         }
 648     }
 649     else if( p_frag->p_buffer[3] == 0xb5 )
 650     {
 651         int i_type = p_frag->p_buffer[4] >> 4;
 652
 653         /* Extension start code */
 654         if( i_type == 0x01 )
 655         {
 656 #if 0
 657             static const int mpeg2_aspect[16][2] =
 658             {
 659                 {0,1}, {1,1}, {4,3}, {16,9}, {221,100},
 660                 {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1},
 661                 {0,1}, {0,1}
 662             };
 663 #endif
 664
 665             /* sequence extension */
 666             if( p_sys->p_ext) block_Release( p_sys->p_ext );
 667             p_sys->p_ext = block_Duplicate( p_frag );
 668
 669             if( p_frag->i_buffer >= 10 )
 670             {
 671                 p_sys->b_seq_progressive =
 672                     p_frag->p_buffer[5]&0x08 ? true : false;
 673                 p_sys->b_low_delay =
 674                     p_frag->p_buffer[9]&0x80 ? true : false;
 675             }
 676
 677             /* Do not set aspect ratio : in case we're transcoding,
 678              * transcode will take our fmt_out as a fmt_in to libmpeg2.
 679              * libmpeg2.c will then believe that the user has requested
 680              * a specific aspect ratio, which she hasn't. Thus in case
 681              * of aspect ratio change, we're screwed. --Meuuh
 682              */
 683 #if 0
 684             p_dec->fmt_out.video.i_aspect =
 685                 mpeg2_aspect[p_sys->i_aspect_ratio_info][0] *
 686                 VOUT_ASPECT_FACTOR /
 687                 mpeg2_aspect[p_sys->i_aspect_ratio_info][1];
 688 #endif
 689
 690         }
 691         else if( i_type == 0x08 )
 692         {
 693             /* picture extension */
 694             p_sys->i_picture_structure = p_frag->p_buffer[6]&0x03;
 695             p_sys->i_top_field_first   = p_frag->p_buffer[7] >> 7;
 696             p_sys->i_repeat_first_field= (p_frag->p_buffer[7]>>1)&0x01;
 697             p_sys->i_progressive_frame = p_frag->p_buffer[8] >> 7;
 698         }
 699     }
 700     else if( p_frag->p_buffer[3] == 0xb2 && p_frag->i_buffer > 4 )
 701     {
 702         cc_Extract( &p_sys->cc, &p_frag->p_buffer[4], p_frag->i_buffer - 4 );
 703     }
 704     else if( p_frag->p_buffer[3] == 0x00 )
 705     {
 706         /* Picture start code */
 707         p_sys->i_seq_old++;
 708
 709         if( p_frag->i_buffer >= 6 )
 710         {
 711             p_sys->i_temporal_ref =
 712                 ( p_frag->p_buffer[4] << 2 )|(p_frag->p_buffer[5] >> 6);
 713             p_sys->i_picture_type = ( p_frag->p_buffer[5] >> 3 ) & 0x03;
 714         }
 715
 716         p_sys->i_dts = p_frag->i_dts;
 717         p_sys->i_pts = p_frag->i_pts;
 718     }
 719     else if( p_frag->p_buffer[3] >= 0x01 && p_frag->p_buffer[3] <= 0xaf )
 720     {
 721         /* Slice start code */
 722         p_sys->b_frame_slice = true;
 723     }
 724
 725     /* Append the block */
 726     block_ChainLastAppend( &p_sys->pp_last, p_frag );
 727
 728     return p_pic;
 729 }