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