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_BytestreamFlush( &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_interpolated_dts =
 276 //        p_sys->i_last_ref_pts = 0;
 277
 278         block_Release( *pp_block );
 279         return NULL;
 280     }
 281
 282
 283     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 284
 285     while( 1 )
 286     {
 287         switch( p_sys->i_state )
 288         {
 289
 290         case STATE_NOSYNC:
 291             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 292                     &p_sys->i_offset, p_sys->p_startcode, 3 ) == VLC_SUCCESS )
 293             {
 294                 p_sys->i_state = STATE_NEXT_SYNC;
 295             }
 296
 297             if( p_sys->i_offset )
 298             {
 299                 block_SkipBytes( &p_sys->bytestream, p_sys->i_offset );
 300                 p_sys->i_offset = 0;
 301                 block_BytestreamFlush( &p_sys->bytestream );
 302             }
 303
 304             if( p_sys->i_state != STATE_NEXT_SYNC )
 305             {
 306                 /* Need more data */
 307                 return NULL;
 308             }
 309
 310             p_sys->i_offset = 1; /* To find next startcode */
 311
 312         case STATE_NEXT_SYNC:
 313             /* TODO: If p_block == NULL, flush the buffer without checking the
 314              * next sync word */
 315
 316             /* Find the next startcode */
 317             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 318                     &p_sys->i_offset, p_sys->p_startcode, 3 ) != VLC_SUCCESS )
 319             {
 320                 /* Need more data */
 321                 return NULL;
 322             }
 323
 324             /* Get the new fragment and set the pts/dts */
 325             p_pic = block_New( p_dec, p_sys->i_offset );
 326             block_BytestreamFlush( &p_sys->bytestream );
 327             p_pic->i_pts = p_sys->bytestream.p_block->i_pts;
 328             p_pic->i_dts = p_sys->bytestream.p_block->i_dts;
 329
 330             block_GetBytes( &p_sys->bytestream, p_pic->p_buffer,
 331                             p_pic->i_buffer );
 332
 333             /* don't reuse the same timestamps several times */
 334             if( p_pic->i_buffer >= 4 && p_pic->p_buffer[3] == 0x00 )
 335             {
 336                 /* We have a picture start code */
 337                 p_sys->bytestream.p_block->i_pts = 0;
 338                 p_sys->bytestream.p_block->i_dts = 0;
 339             }
 340
 341             p_sys->i_offset = 0;
 342
 343             /* Get picture if any */
 344             if( !( p_pic = ParseMPEGBlock( p_dec, p_pic ) ) )
 345             {
 346                 p_sys->i_state = STATE_NOSYNC;
 347                 break;
 348             }
 349
 350             /* If a discontinuity has been encountered, then wait till
 351              * the next Intra frame before continuing with packetizing */
 352             if( p_sys->b_discontinuity &&
 353                 p_sys->b_sync_on_intra_frame )
 354             {
 355                 if( p_pic->i_flags & BLOCK_FLAG_TYPE_I )
 356                 {
 357                     msg_Dbg( p_dec, "synced on intra frame" );
 358                     p_sys->b_discontinuity = false;
 359                     p_pic->i_flags |= BLOCK_FLAG_DISCONTINUITY;
 360                 }
 361                 else
 362                 {
 363                     msg_Dbg( p_dec, "waiting on intra frame" );
 364                     p_sys->i_state = STATE_NOSYNC;
 365                     block_Release( p_pic );
 366                     break;
 367                 }
 368             }
 369
 370             /* We've just started the stream, wait for the first PTS.
 371              * We discard here so we can still get the sequence header. */
 372             if( p_sys->i_dts <= 0 && p_sys->i_pts <= 0 &&
 373                 p_sys->i_interpolated_dts <= 0 )
 374             {
 375                 msg_Dbg( p_dec, "need a starting pts/dts" );
 376                 p_sys->i_state = STATE_NOSYNC;
 377                 block_Release( p_pic );
 378                 break;
 379             }
 380
 381             /* When starting the stream we can have the first frame with
 382              * a null DTS (i_interpolated_pts is initialized to 0) */
 383             if( !p_pic->i_dts ) p_pic->i_dts = p_pic->i_pts;
 384
 385             /* So p_block doesn't get re-added several times */
 386             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 387
 388             p_sys->i_state = STATE_NOSYNC;
 389
 390             return p_pic;
 391         }
 392     }
 393 }
 394
 395 /*****************************************************************************
 396  * GetCc:
 397  *****************************************************************************/
 398 static block_t *GetCc( decoder_t *p_dec, bool pb_present[4] )
 399 {
 400     decoder_sys_t *p_sys = p_dec->p_sys;
 401     block_t *p_cc;
 402     int i;
 403
 404     for( i = 0; i < 4; i++ )
 405         pb_present[i] = p_sys->cc.pb_present[i];
 406
 407     if( p_sys->cc.i_data <= 0 )
 408         return NULL;
 409
 410     p_cc = block_New( p_dec, p_sys->cc.i_data);
 411     if( p_cc )
 412     {
 413         memcpy( p_cc->p_buffer, p_sys->cc.p_data, p_sys->cc.i_data );
 414         p_cc->i_dts =
 415         p_cc->i_pts = p_sys->cc.b_reorder ? p_sys->i_cc_pts : p_sys->i_cc_dts;
 416         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);
 417     }
 418     cc_Flush( &p_sys->cc );
 419     return p_cc;
 420 }
 421
 422 /*****************************************************************************
 423  * ParseMPEGBlock: Re-assemble fragments into a block containing a picture
 424  *****************************************************************************/
 425 static block_t *ParseMPEGBlock( decoder_t *p_dec, block_t *p_frag )
 426 {
 427     decoder_sys_t *p_sys = p_dec->p_sys;
 428     block_t *p_pic = NULL;
 429
 430     /*
 431      * Check if previous picture is finished
 432      */
 433     if( ( p_sys->b_frame_slice &&
 434           (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) ) &&
 435           p_sys->p_seq == NULL )
 436     {
 437         /* We have a picture but without a sequence header we can't
 438          * do anything */
 439         msg_Dbg( p_dec, "waiting for sequence start" );
 440         if( p_sys->p_frame ) block_ChainRelease( p_sys->p_frame );
 441         p_sys->p_frame = NULL;
 442         p_sys->pp_last = &p_sys->p_frame;
 443         p_sys->b_frame_slice = false;
 444
 445     }
 446     else if( p_sys->b_frame_slice &&
 447              (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) )
 448     {
 449         const bool b_eos = p_frag->p_buffer[3] == 0xb7;
 450
 451         mtime_t i_duration;
 452
 453         if( b_eos )
 454         {
 455             block_ChainLastAppend( &p_sys->pp_last, p_frag );
 456             p_frag = NULL;
 457         }
 458
 459         p_pic = block_ChainGather( p_sys->p_frame );
 460
 461         if( b_eos )
 462             p_pic->i_flags |= BLOCK_FLAG_END_OF_SEQUENCE;
 463
 464         i_duration = (mtime_t)( 1000000 * p_sys->i_frame_rate_base /
 465                                 p_sys->i_frame_rate );
 466
 467         if( !p_sys->b_seq_progressive && p_sys->i_picture_structure != 0x03 )
 468         {
 469             i_duration /= 2;
 470         }
 471
 472         if( p_sys->b_seq_progressive )
 473         {
 474             if( p_sys->i_top_field_first == 0 &&
 475                 p_sys->i_repeat_first_field == 1 )
 476             {
 477                 i_duration *= 2;
 478             }
 479             else if( p_sys->i_top_field_first == 1 &&
 480                      p_sys->i_repeat_first_field == 1 )
 481             {
 482                 i_duration *= 3;
 483             }
 484         }
 485         else
 486         {
 487             if( p_sys->i_picture_structure == 0x03 )
 488             {
 489                 if( p_sys->i_progressive_frame && p_sys->i_repeat_first_field )
 490                 {
 491                     i_duration += i_duration / 2;
 492                 }
 493             }
 494         }
 495
 496         if( p_sys->b_low_delay || p_sys->i_picture_type == 0x03 )
 497         {
 498             /* Trivial case (DTS == PTS) */
 499             /* Correct interpolated dts when we receive a new pts/dts */
 500             if( p_sys->i_pts > 0 ) p_sys->i_interpolated_dts = p_sys->i_pts;
 501             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 502         }
 503         else
 504         {
 505             /* Correct interpolated dts when we receive a new pts/dts */
 506             if( p_sys->i_last_ref_pts > 0 && !p_sys->b_second_field )
 507                 p_sys->i_interpolated_dts = p_sys->i_last_ref_pts;
 508             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 509
 510             if( !p_sys->b_second_field )
 511                 p_sys->i_last_ref_pts = p_sys->i_pts;
 512         }
 513
 514         p_pic->i_dts = p_sys->i_interpolated_dts;
 515         p_sys->i_interpolated_dts += i_duration;
 516
 517         /* Set PTS only if we have a B frame or if it comes from the stream */
 518         if( p_sys->i_pts > 0 )
 519         {
 520             p_pic->i_pts = p_sys->i_pts;
 521         }
 522         else if( p_sys->i_picture_type == 0x03 )
 523         {
 524             p_pic->i_pts = p_pic->i_dts;
 525         }
 526         else
 527         {
 528             p_pic->i_pts = 0;
 529         }
 530
 531         switch ( p_sys->i_picture_type )
 532         {
 533         case 0x01:
 534             p_pic->i_flags |= BLOCK_FLAG_TYPE_I;
 535             break;
 536         case 0x02:
 537             p_pic->i_flags |= BLOCK_FLAG_TYPE_P;
 538             break;
 539         case 0x03:
 540             p_pic->i_flags |= BLOCK_FLAG_TYPE_B;
 541             break;
 542         }
 543
 544         p_pic->i_length = p_sys->i_interpolated_dts - p_pic->i_dts;
 545
 546 #if 0
 547         msg_Dbg( p_dec, "pic: type=%d dts=%"PRId64" pts-dts=%"PRId64,
 548         p_sys->i_picture_type, p_pic->i_dts, p_pic->i_pts - p_pic->i_dts);
 549 #endif
 550
 551         /* Reset context */
 552         p_sys->p_frame = NULL;
 553         p_sys->pp_last = &p_sys->p_frame;
 554         p_sys->b_frame_slice = false;
 555
 556         if( p_sys->i_picture_structure != 0x03 )
 557         {
 558             p_sys->b_second_field = !p_sys->b_second_field;
 559         }
 560         else
 561         {
 562             p_sys->b_second_field = 0;
 563         }
 564
 565         /* CC */
 566         p_sys->b_cc_reset = true;
 567         p_sys->i_cc_pts = p_pic->i_pts;
 568         p_sys->i_cc_dts = p_pic->i_dts;
 569         p_sys->i_cc_flags = p_pic->i_flags;
 570     }
 571
 572     if( !p_pic && p_sys->b_cc_reset )
 573     {
 574         p_sys->b_cc_reset = false;
 575         cc_Flush( &p_sys->cc );
 576     }
 577
 578     if( !p_frag )
 579         return p_pic;
 580     /*
 581      * Check info of current fragment
 582      */
 583     if( p_frag->p_buffer[3] == 0xb8 )
 584     {
 585         /* Group start code */
 586         if( p_sys->p_seq &&
 587             p_sys->i_seq_old > p_sys->i_frame_rate/p_sys->i_frame_rate_base )
 588         {
 589             /* Usefull for mpeg1: repeat sequence header every second */
 590             block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_seq ) );
 591             if( p_sys->p_ext )
 592             {
 593                 block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_ext ) );
 594             }
 595
 596             p_sys->i_seq_old = 0;
 597         }
 598     }
 599     else if( p_frag->p_buffer[3] == 0xb3 && p_frag->i_buffer >= 8 )
 600     {
 601         /* Sequence header code */
 602         static const int code_to_frame_rate[16][2] =
 603         {
 604             { 1, 1 },  /* invalid */
 605             { 24000, 1001 }, { 24, 1 }, { 25, 1 },       { 30000, 1001 },
 606             { 30, 1 },       { 50, 1 }, { 60000, 1001 }, { 60, 1 },
 607             /* Unofficial 15fps from Xing*/
 608             { 15, 1001 },
 609             /* Unofficial economy rates from libmpeg3 */
 610             { 5, 1001 }, { 10, 1001 }, { 12, 1001 }, { 15, 1001 },
 611             { 1, 1 },  { 1, 1 }  /* invalid */
 612         };
 613
 614         if( p_sys->p_seq ) block_Release( p_sys->p_seq );
 615         if( p_sys->p_ext ) block_Release( p_sys->p_ext );
 616
 617         p_sys->p_seq = block_Duplicate( p_frag );
 618         p_sys->i_seq_old = 0;
 619         p_sys->p_ext = NULL;
 620
 621         p_dec->fmt_out.video.i_width =
 622             ( p_frag->p_buffer[4] << 4)|(p_frag->p_buffer[5] >> 4 );
 623         p_dec->fmt_out.video.i_height =
 624             ( (p_frag->p_buffer[5]&0x0f) << 8 )|p_frag->p_buffer[6];
 625         p_sys->i_aspect_ratio_info = p_frag->p_buffer[7] >> 4;
 626
 627         /* TODO: MPEG1 aspect ratio */
 628
 629         p_sys->i_frame_rate = code_to_frame_rate[p_frag->p_buffer[7]&0x0f][0];
 630         p_sys->i_frame_rate_base =
 631             code_to_frame_rate[p_frag->p_buffer[7]&0x0f][1];
 632
 633         p_dec->fmt_out.video.i_frame_rate = p_sys->i_frame_rate;
 634         p_dec->fmt_out.video.i_frame_rate_base = p_sys->i_frame_rate_base;
 635
 636         p_sys->b_seq_progressive = true;
 637         p_sys->b_low_delay = true;
 638
 639         if ( !p_sys->b_inited )
 640         {
 641             msg_Dbg( p_dec, "size %dx%d fps=%.3f",
 642                  p_dec->fmt_out.video.i_width, p_dec->fmt_out.video.i_height,
 643                  p_sys->i_frame_rate / (float)p_sys->i_frame_rate_base );
 644             p_sys->b_inited = 1;
 645         }
 646     }
 647     else if( p_frag->p_buffer[3] == 0xb5 )
 648     {
 649         int i_type = p_frag->p_buffer[4] >> 4;
 650
 651         /* Extension start code */
 652         if( i_type == 0x01 )
 653         {
 654 #if 0
 655             static const int mpeg2_aspect[16][2] =
 656             {
 657                 {0,1}, {1,1}, {4,3}, {16,9}, {221,100},
 658                 {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1},
 659                 {0,1}, {0,1}
 660             };
 661 #endif
 662
 663             /* sequence extension */
 664             if( p_sys->p_ext) block_Release( p_sys->p_ext );
 665             p_sys->p_ext = block_Duplicate( p_frag );
 666
 667             if( p_frag->i_buffer >= 10 )
 668             {
 669                 p_sys->b_seq_progressive =
 670                     p_frag->p_buffer[5]&0x08 ? true : false;
 671                 p_sys->b_low_delay =
 672                     p_frag->p_buffer[9]&0x80 ? true : false;
 673             }
 674
 675             /* Do not set aspect ratio : in case we're transcoding,
 676              * transcode will take our fmt_out as a fmt_in to libmpeg2.
 677              * libmpeg2.c will then believe that the user has requested
 678              * a specific aspect ratio, which she hasn't. Thus in case
 679              * of aspect ratio change, we're screwed. --Meuuh
 680              */
 681 #if 0
 682             p_dec->fmt_out.video.i_aspect =
 683                 mpeg2_aspect[p_sys->i_aspect_ratio_info][0] *
 684                 VOUT_ASPECT_FACTOR /
 685                 mpeg2_aspect[p_sys->i_aspect_ratio_info][1];
 686 #endif
 687
 688         }
 689         else if( i_type == 0x08 )
 690         {
 691             /* picture extension */
 692             p_sys->i_picture_structure = p_frag->p_buffer[6]&0x03;
 693             p_sys->i_top_field_first   = p_frag->p_buffer[7] >> 7;
 694             p_sys->i_repeat_first_field= (p_frag->p_buffer[7]>>1)&0x01;
 695             p_sys->i_progressive_frame = p_frag->p_buffer[8] >> 7;
 696         }
 697     }
 698     else if( p_frag->p_buffer[3] == 0xb2 && p_frag->i_buffer > 4 )
 699     {
 700         cc_Extract( &p_sys->cc, &p_frag->p_buffer[4], p_frag->i_buffer - 4 );
 701     }
 702     else if( p_frag->p_buffer[3] == 0x00 )
 703     {
 704         /* Picture start code */
 705         p_sys->i_seq_old++;
 706
 707         if( p_frag->i_buffer >= 6 )
 708         {
 709             p_sys->i_temporal_ref =
 710                 ( p_frag->p_buffer[4] << 2 )|(p_frag->p_buffer[5] >> 6);
 711             p_sys->i_picture_type = ( p_frag->p_buffer[5] >> 3 ) & 0x03;
 712         }
 713
 714         p_sys->i_dts = p_frag->i_dts;
 715         p_sys->i_pts = p_frag->i_pts;
 716     }
 717     else if( p_frag->p_buffer[3] >= 0x01 && p_frag->p_buffer[3] <= 0xaf )
 718     {
 719         /* Slice start code */
 720         p_sys->b_frame_slice = true;
 721     }
 722
 723     /* Append the block */
 724     block_ChainLastAppend( &p_sys->pp_last, p_frag );
 725
 726     return p_pic;
 727 }