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         change_safe();
  72 vlc_module_end();
  73
  74 /*****************************************************************************
  75  * Local prototypes
  76  *****************************************************************************/
  77 static block_t *Packetize( decoder_t *, block_t ** );
  78 static block_t *ParseMPEGBlock( decoder_t *, block_t * );
  79 static block_t *GetCc( decoder_t *p_dec, vlc_bool_t pb_present[4] );
  80
  81 struct decoder_sys_t
  82 {
  83     /*
  84      * Input properties
  85      */
  86     block_bytestream_t bytestream;
  87     int i_state;
  88     int i_offset;
  89     uint8_t p_startcode[3];
  90
  91     /* Sequence header and extension */
  92     block_t *p_seq;
  93     block_t *p_ext;
  94
  95     /* Current frame being built */
  96     block_t    *p_frame;
  97     block_t    **pp_last;
  98
  99     vlc_bool_t b_frame_slice;
 100     mtime_t i_pts;
 101     mtime_t i_dts;
 102
 103     /* Sequence properties */
 104     int         i_frame_rate;
 105     int         i_frame_rate_base;
 106     vlc_bool_t  b_seq_progressive;
 107     vlc_bool_t  b_low_delay;
 108     int         i_aspect_ratio_info;
 109     vlc_bool_t  b_inited;
 110
 111     /* Picture properties */
 112     int i_temporal_ref;
 113     int i_picture_type;
 114     int i_picture_structure;
 115     int i_top_field_first;
 116     int i_repeat_first_field;
 117     int i_progressive_frame;
 118
 119     mtime_t i_interpolated_dts;
 120     mtime_t i_last_ref_pts;
 121     vlc_bool_t b_second_field;
 122
 123     /* Number of pictures since last sequence header */
 124     int i_seq_old;
 125
 126     /* Sync behaviour */
 127     vlc_bool_t  b_sync_on_intra_frame;
 128     vlc_bool_t  b_discontinuity;
 129
 130     /* */
 131     vlc_bool_t b_cc_reset;
 132     uint32_t i_cc_flags;
 133     mtime_t i_cc_pts;
 134     mtime_t i_cc_dts;
 135     cc_data_t cc;
 136 };
 137
 138 enum {
 139     STATE_NOSYNC,
 140     STATE_NEXT_SYNC
 141 };
 142
 143 /*****************************************************************************
 144  * Open:
 145  *****************************************************************************/
 146 static int Open( vlc_object_t *p_this )
 147 {
 148     decoder_t *p_dec = (decoder_t*)p_this;
 149     decoder_sys_t *p_sys;
 150
 151     if( p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', '1' ) &&
 152         p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', '2' ) &&
 153         p_dec->fmt_in.i_codec != VLC_FOURCC( 'm', 'p', 'g', 'v' ) )
 154     {
 155         return VLC_EGENERIC;
 156     }
 157
 158     es_format_Init( &p_dec->fmt_out, VIDEO_ES, VLC_FOURCC('m','p','g','v') );
 159     p_dec->pf_packetize = Packetize;
 160     p_dec->pf_get_cc = GetCc;
 161
 162     p_dec->p_sys = p_sys = malloc( sizeof( decoder_sys_t ) );
 163
 164     /* Misc init */
 165     p_sys->i_state = STATE_NOSYNC;
 166     p_sys->bytestream = block_BytestreamInit( p_dec );
 167     p_sys->p_startcode[0] = 0;
 168     p_sys->p_startcode[1] = 0;
 169     p_sys->p_startcode[2] = 1;
 170     p_sys->i_offset = 0;
 171
 172     p_sys->p_seq = NULL;
 173     p_sys->p_ext = NULL;
 174     p_sys->p_frame = NULL;
 175     p_sys->pp_last = &p_sys->p_frame;
 176     p_sys->b_frame_slice = VLC_FALSE;
 177
 178     p_sys->i_dts = p_sys->i_pts = 0;
 179
 180     p_sys->i_frame_rate = 1;
 181     p_sys->i_frame_rate_base = 1;
 182     p_sys->b_seq_progressive = VLC_TRUE;
 183     p_sys->b_low_delay = VLC_TRUE;
 184     p_sys->i_seq_old = 0;
 185
 186     p_sys->i_temporal_ref = 0;
 187     p_sys->i_picture_type = 0;
 188     p_sys->i_picture_structure = 0x03; /* frame */
 189     p_sys->i_top_field_first = 0;
 190     p_sys->i_repeat_first_field = 0;
 191     p_sys->i_progressive_frame = 0;
 192     p_sys->b_inited = 0;
 193
 194     p_sys->i_interpolated_dts = 0;
 195     p_sys->i_last_ref_pts = 0;
 196     p_sys->b_second_field = 0;
 197
 198     p_sys->b_discontinuity = VLC_FALSE;
 199     p_sys->b_sync_on_intra_frame = var_CreateGetBool( p_dec, "packetizer-mpegvideo-sync-iframe" );
 200     if( p_sys->b_sync_on_intra_frame )
 201         msg_Dbg( p_dec, "syncing on intra frame now" );
 202
 203     p_sys->b_cc_reset = VLC_FALSE;
 204     p_sys->i_cc_pts = 0;
 205     p_sys->i_cc_dts = 0;
 206     p_sys->i_cc_flags = 0;
 207     cc_Init( &p_sys->cc );
 208
 209     return VLC_SUCCESS;
 210 }
 211
 212 /*****************************************************************************
 213  * Close:
 214  *****************************************************************************/
 215 static void Close( vlc_object_t *p_this )
 216 {
 217     decoder_t     *p_dec = (decoder_t*)p_this;
 218     decoder_sys_t *p_sys = p_dec->p_sys;
 219
 220     block_BytestreamRelease( &p_sys->bytestream );
 221
 222     if( p_sys->p_seq )
 223     {
 224         block_Release( p_sys->p_seq );
 225     }
 226     if( p_sys->p_ext )
 227     {
 228         block_Release( p_sys->p_ext );
 229     }
 230     if( p_sys->p_frame )
 231     {
 232         block_ChainRelease( p_sys->p_frame );
 233     }
 234
 235     var_Destroy( p_dec, "packetizer-mpegvideo-sync-iframe" );
 236
 237     free( p_sys );
 238 }
 239
 240 /*****************************************************************************
 241  * Packetize:
 242  *****************************************************************************/
 243 static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
 244 {
 245     decoder_sys_t *p_sys = p_dec->p_sys;
 246     block_t       *p_pic;
 247
 248     if( pp_block == NULL || *pp_block == NULL )
 249     {
 250         return NULL;
 251     }
 252
 253     if( (*pp_block)->i_flags&(BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 254     {
 255         if( (*pp_block)->i_flags&BLOCK_FLAG_CORRUPTED )
 256         {
 257             p_sys->i_state = STATE_NOSYNC;
 258             block_BytestreamFlush( &p_sys->bytestream );
 259
 260             p_sys->b_discontinuity = VLC_TRUE;
 261             if( p_sys->p_frame )
 262                 block_ChainRelease( p_sys->p_frame );
 263             p_sys->p_frame = NULL;
 264             p_sys->pp_last = &p_sys->p_frame;
 265             p_sys->b_frame_slice = VLC_FALSE;
 266         }
 267 //        p_sys->i_interpolated_dts =
 268 //        p_sys->i_last_ref_pts = 0;
 269
 270         block_Release( *pp_block );
 271         return NULL;
 272     }
 273
 274
 275     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 276
 277     while( 1 )
 278     {
 279         switch( p_sys->i_state )
 280         {
 281
 282         case STATE_NOSYNC:
 283             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 284                     &p_sys->i_offset, p_sys->p_startcode, 3 ) == VLC_SUCCESS )
 285             {
 286                 p_sys->i_state = STATE_NEXT_SYNC;
 287             }
 288
 289             if( p_sys->i_offset )
 290             {
 291                 block_SkipBytes( &p_sys->bytestream, p_sys->i_offset );
 292                 p_sys->i_offset = 0;
 293                 block_BytestreamFlush( &p_sys->bytestream );
 294             }
 295
 296             if( p_sys->i_state != STATE_NEXT_SYNC )
 297             {
 298                 /* Need more data */
 299                 return NULL;
 300             }
 301
 302             p_sys->i_offset = 1; /* To find next startcode */
 303
 304         case STATE_NEXT_SYNC:
 305             /* TODO: If p_block == NULL, flush the buffer without checking the
 306              * next sync word */
 307
 308             /* Find the next startcode */
 309             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 310                     &p_sys->i_offset, p_sys->p_startcode, 3 ) != VLC_SUCCESS )
 311             {
 312                 /* Need more data */
 313                 return NULL;
 314             }
 315
 316             /* Get the new fragment and set the pts/dts */
 317             p_pic = block_New( p_dec, p_sys->i_offset );
 318             block_BytestreamFlush( &p_sys->bytestream );
 319             p_pic->i_pts = p_sys->bytestream.p_block->i_pts;
 320             p_pic->i_dts = p_sys->bytestream.p_block->i_dts;
 321
 322             block_GetBytes( &p_sys->bytestream, p_pic->p_buffer,
 323                             p_pic->i_buffer );
 324
 325             /* don't reuse the same timestamps several times */
 326             if( p_pic->i_buffer >= 4 && p_pic->p_buffer[3] == 0x00 )
 327             {
 328                 /* We have a picture start code */
 329                 p_sys->bytestream.p_block->i_pts = 0;
 330                 p_sys->bytestream.p_block->i_dts = 0;
 331             }
 332
 333             p_sys->i_offset = 0;
 334
 335             /* Get picture if any */
 336             if( !( p_pic = ParseMPEGBlock( p_dec, p_pic ) ) )
 337             {
 338                 p_sys->i_state = STATE_NOSYNC;
 339                 break;
 340             }
 341
 342             /* If a discontinuity has been encountered, then wait till
 343              * the next Intra frame before continuing with packetizing */
 344             if( p_sys->b_discontinuity &&
 345                 p_sys->b_sync_on_intra_frame )
 346             {
 347                 if( p_pic->i_flags & BLOCK_FLAG_TYPE_I )
 348                 {
 349                     msg_Dbg( p_dec, "synced on intra frame" );
 350                     p_sys->b_discontinuity = VLC_FALSE;
 351                     p_pic->i_flags |= BLOCK_FLAG_DISCONTINUITY;
 352                 }
 353                 else
 354                 {
 355                     msg_Dbg( p_dec, "waiting on intra frame" );
 356                     p_sys->i_state = STATE_NOSYNC;
 357                     block_Release( p_pic );
 358                     break;
 359                 }
 360             }
 361
 362             /* We've just started the stream, wait for the first PTS.
 363              * We discard here so we can still get the sequence header. */
 364             if( p_sys->i_dts <= 0 && p_sys->i_pts <= 0 &&
 365                 p_sys->i_interpolated_dts <= 0 )
 366             {
 367                 msg_Dbg( p_dec, "need a starting pts/dts" );
 368                 p_sys->i_state = STATE_NOSYNC;
 369                 block_Release( p_pic );
 370                 break;
 371             }
 372
 373             /* When starting the stream we can have the first frame with
 374              * a null DTS (i_interpolated_pts is initialized to 0) */
 375             if( !p_pic->i_dts ) p_pic->i_dts = p_pic->i_pts;
 376
 377             /* So p_block doesn't get re-added several times */
 378             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 379
 380             p_sys->i_state = STATE_NOSYNC;
 381
 382             return p_pic;
 383         }
 384     }
 385 }
 386
 387 /*****************************************************************************
 388  * GetCc:
 389  *****************************************************************************/
 390 static block_t *GetCc( decoder_t *p_dec, vlc_bool_t pb_present[4] )
 391 {
 392     decoder_sys_t *p_sys = p_dec->p_sys;
 393     block_t *p_cc;
 394     int i;
 395
 396     for( i = 0; i < 4; i++ )
 397         pb_present[i] = p_sys->cc.pb_present[i];
 398
 399     if( p_sys->cc.i_data <= 0 )
 400         return NULL;
 401
 402     p_cc = block_New( p_dec, p_sys->cc.i_data);
 403     if( p_cc )
 404     {
 405         memcpy( p_cc->p_buffer, p_sys->cc.p_data, p_sys->cc.i_data );
 406         p_cc->i_dts =
 407         p_cc->i_pts = p_sys->cc.b_reorder ? p_sys->i_cc_pts : p_sys->i_cc_dts;
 408         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);
 409     }
 410     cc_Flush( &p_sys->cc );
 411     return p_cc;
 412 }
 413
 414 /*****************************************************************************
 415  * ParseMPEGBlock: Re-assemble fragments into a block containing a picture
 416  *****************************************************************************/
 417 static block_t *ParseMPEGBlock( decoder_t *p_dec, block_t *p_frag )
 418 {
 419     decoder_sys_t *p_sys = p_dec->p_sys;
 420     block_t *p_pic = NULL;
 421
 422     /*
 423      * Check if previous picture is finished
 424      */
 425     if( ( p_sys->b_frame_slice &&
 426           (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) ) &&
 427           p_sys->p_seq == NULL )
 428     {
 429         /* We have a picture but without a sequence header we can't
 430          * do anything */
 431         msg_Dbg( p_dec, "waiting for sequence start" );
 432         if( p_sys->p_frame ) block_ChainRelease( p_sys->p_frame );
 433         p_sys->p_frame = NULL;
 434         p_sys->pp_last = &p_sys->p_frame;
 435         p_sys->b_frame_slice = VLC_FALSE;
 436
 437     }
 438     else if( p_sys->b_frame_slice &&
 439              (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) )
 440     {
 441         mtime_t i_duration;
 442
 443         p_pic = block_ChainGather( p_sys->p_frame );
 444
 445         i_duration = (mtime_t)( 1000000 * p_sys->i_frame_rate_base /
 446                                 p_sys->i_frame_rate );
 447
 448         if( !p_sys->b_seq_progressive && p_sys->i_picture_structure != 0x03 )
 449         {
 450             i_duration /= 2;
 451         }
 452
 453         if( p_sys->b_seq_progressive )
 454         {
 455             if( p_sys->i_top_field_first == 0 &&
 456                 p_sys->i_repeat_first_field == 1 )
 457             {
 458                 i_duration *= 2;
 459             }
 460             else if( p_sys->i_top_field_first == 1 &&
 461                      p_sys->i_repeat_first_field == 1 )
 462             {
 463                 i_duration *= 3;
 464             }
 465         }
 466         else
 467         {
 468             if( p_sys->i_picture_structure == 0x03 )
 469             {
 470                 if( p_sys->i_progressive_frame && p_sys->i_repeat_first_field )
 471                 {
 472                     i_duration += i_duration / 2;
 473                 }
 474             }
 475         }
 476
 477         if( p_sys->b_low_delay || p_sys->i_picture_type == 0x03 )
 478         {
 479             /* Trivial case (DTS == PTS) */
 480             /* Correct interpolated dts when we receive a new pts/dts */
 481             if( p_sys->i_pts > 0 ) p_sys->i_interpolated_dts = p_sys->i_pts;
 482             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 483         }
 484         else
 485         {
 486             /* Correct interpolated dts when we receive a new pts/dts */
 487             if( p_sys->i_last_ref_pts > 0 && !p_sys->b_second_field )
 488                 p_sys->i_interpolated_dts = p_sys->i_last_ref_pts;
 489             if( p_sys->i_dts > 0 ) p_sys->i_interpolated_dts = p_sys->i_dts;
 490
 491             if( !p_sys->b_second_field )
 492                 p_sys->i_last_ref_pts = p_sys->i_pts;
 493         }
 494
 495         p_pic->i_dts = p_sys->i_interpolated_dts;
 496         p_sys->i_interpolated_dts += i_duration;
 497
 498         /* Set PTS only if we have a B frame or if it comes from the stream */
 499         if( p_sys->i_pts > 0 )
 500         {
 501             p_pic->i_pts = p_sys->i_pts;
 502         }
 503         else if( p_sys->i_picture_type == 0x03 )
 504         {
 505             p_pic->i_pts = p_pic->i_dts;
 506         }
 507         else
 508         {
 509             p_pic->i_pts = 0;
 510         }
 511
 512         switch ( p_sys->i_picture_type )
 513         {
 514         case 0x01:
 515             p_pic->i_flags |= BLOCK_FLAG_TYPE_I;
 516             break;
 517         case 0x02:
 518             p_pic->i_flags |= BLOCK_FLAG_TYPE_P;
 519             break;
 520         case 0x03:
 521             p_pic->i_flags |= BLOCK_FLAG_TYPE_B;
 522             break;
 523         }
 524
 525         p_pic->i_length = p_sys->i_interpolated_dts - p_pic->i_dts;
 526
 527 #if 0
 528         msg_Dbg( p_dec, "pic: type=%d dts="I64Fd" pts-dts="I64Fd,
 529         p_sys->i_picture_type, p_pic->i_dts, p_pic->i_pts - p_pic->i_dts);
 530 #endif
 531
 532         /* Reset context */
 533         p_sys->p_frame = NULL;
 534         p_sys->pp_last = &p_sys->p_frame;
 535         p_sys->b_frame_slice = VLC_FALSE;
 536
 537         if( p_sys->i_picture_structure != 0x03 )
 538         {
 539             p_sys->b_second_field = !p_sys->b_second_field;
 540         }
 541         else
 542         {
 543             p_sys->b_second_field = 0;
 544         }
 545
 546         /* CC */
 547         p_sys->b_cc_reset = VLC_TRUE;
 548         p_sys->i_cc_pts = p_pic->i_pts;
 549         p_sys->i_cc_dts = p_pic->i_dts;
 550         p_sys->i_cc_flags = p_pic->i_flags;
 551     }
 552
 553     if( !p_pic && p_sys->b_cc_reset )
 554     {
 555         p_sys->b_cc_reset = VLC_FALSE;
 556         cc_Flush( &p_sys->cc );
 557     }
 558
 559     /*
 560      * Check info of current fragment
 561      */
 562     if( p_frag->p_buffer[3] == 0xb8 )
 563     {
 564         /* Group start code */
 565         if( p_sys->p_seq &&
 566             p_sys->i_seq_old > p_sys->i_frame_rate/p_sys->i_frame_rate_base )
 567         {
 568             /* Usefull for mpeg1: repeat sequence header every second */
 569             block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_seq ) );
 570             if( p_sys->p_ext )
 571             {
 572                 block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_ext ) );
 573             }
 574
 575             p_sys->i_seq_old = 0;
 576         }
 577     }
 578     else if( p_frag->p_buffer[3] == 0xb3 && p_frag->i_buffer >= 8 )
 579     {
 580         /* Sequence header code */
 581         static const int code_to_frame_rate[16][2] =
 582         {
 583             { 1, 1 },  /* invalid */
 584             { 24000, 1001 }, { 24, 1 }, { 25, 1 },       { 30000, 1001 },
 585             { 30, 1 },       { 50, 1 }, { 60000, 1001 }, { 60, 1 },
 586             /* Unofficial 15fps from Xing*/
 587             { 15, 1001 },
 588             /* Unofficial economy rates from libmpeg3 */
 589             { 5, 1001 }, { 10, 1001 }, { 12, 1001 }, { 15, 1001 },
 590             { 1, 1 },  { 1, 1 }  /* invalid */
 591         };
 592
 593         if( p_sys->p_seq ) block_Release( p_sys->p_seq );
 594         if( p_sys->p_ext ) block_Release( p_sys->p_ext );
 595
 596         p_sys->p_seq = block_Duplicate( p_frag );
 597         p_sys->i_seq_old = 0;
 598         p_sys->p_ext = NULL;
 599
 600         p_dec->fmt_out.video.i_width =
 601             ( p_frag->p_buffer[4] << 4)|(p_frag->p_buffer[5] >> 4 );
 602         p_dec->fmt_out.video.i_height =
 603             ( (p_frag->p_buffer[5]&0x0f) << 8 )|p_frag->p_buffer[6];
 604         p_sys->i_aspect_ratio_info = p_frag->p_buffer[7] >> 4;
 605
 606         /* TODO: MPEG1 aspect ratio */
 607
 608         p_sys->i_frame_rate = code_to_frame_rate[p_frag->p_buffer[7]&0x0f][0];
 609         p_sys->i_frame_rate_base =
 610             code_to_frame_rate[p_frag->p_buffer[7]&0x0f][1];
 611
 612         p_dec->fmt_out.video.i_frame_rate = p_sys->i_frame_rate;
 613         p_dec->fmt_out.video.i_frame_rate_base = p_sys->i_frame_rate_base;
 614
 615         p_sys->b_seq_progressive = VLC_TRUE;
 616         p_sys->b_low_delay = VLC_TRUE;
 617
 618         if ( !p_sys->b_inited )
 619         {
 620             msg_Dbg( p_dec, "size %dx%d fps=%.3f",
 621                  p_dec->fmt_out.video.i_width, p_dec->fmt_out.video.i_height,
 622                  p_sys->i_frame_rate / (float)p_sys->i_frame_rate_base );
 623             p_sys->b_inited = 1;
 624         }
 625     }
 626     else if( p_frag->p_buffer[3] == 0xb5 )
 627     {
 628         int i_type = p_frag->p_buffer[4] >> 4;
 629
 630         /* Extension start code */
 631         if( i_type == 0x01 )
 632         {
 633 #if 0
 634             static const int mpeg2_aspect[16][2] =
 635             {
 636                 {0,1}, {1,1}, {4,3}, {16,9}, {221,100},
 637                 {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1},
 638                 {0,1}, {0,1}
 639             };
 640 #endif
 641
 642             /* sequence extension */
 643             if( p_sys->p_ext) block_Release( p_sys->p_ext );
 644             p_sys->p_ext = block_Duplicate( p_frag );
 645
 646             if( p_frag->i_buffer >= 10 )
 647             {
 648                 p_sys->b_seq_progressive =
 649                     p_frag->p_buffer[5]&0x08 ? VLC_TRUE : VLC_FALSE;
 650                 p_sys->b_low_delay =
 651                     p_frag->p_buffer[9]&0x80 ? VLC_TRUE : VLC_FALSE;
 652             }
 653
 654             /* Do not set aspect ratio : in case we're transcoding,
 655              * transcode will take our fmt_out as a fmt_in to libmpeg2.
 656              * libmpeg2.c will then believe that the user has requested
 657              * a specific aspect ratio, which she hasn't. Thus in case
 658              * of aspect ratio change, we're screwed. --Meuuh
 659              */
 660 #if 0
 661             p_dec->fmt_out.video.i_aspect =
 662                 mpeg2_aspect[p_sys->i_aspect_ratio_info][0] *
 663                 VOUT_ASPECT_FACTOR /
 664                 mpeg2_aspect[p_sys->i_aspect_ratio_info][1];
 665 #endif
 666
 667         }
 668         else if( i_type == 0x08 )
 669         {
 670             /* picture extension */
 671             p_sys->i_picture_structure = p_frag->p_buffer[6]&0x03;
 672             p_sys->i_top_field_first   = p_frag->p_buffer[7] >> 7;
 673             p_sys->i_repeat_first_field= (p_frag->p_buffer[7]>>1)&0x01;
 674             p_sys->i_progressive_frame = p_frag->p_buffer[8] >> 7;
 675         }
 676     }
 677     else if( p_frag->p_buffer[3] == 0xb2 && p_frag->i_buffer > 4 )
 678     {
 679         cc_Extract( &p_sys->cc, &p_frag->p_buffer[4], p_frag->i_buffer - 4 );
 680     }
 681     else if( p_frag->p_buffer[3] == 0x00 )
 682     {
 683         /* Picture start code */
 684         p_sys->i_seq_old++;
 685
 686         if( p_frag->i_buffer >= 6 )
 687         {
 688             p_sys->i_temporal_ref =
 689                 ( p_frag->p_buffer[4] << 2 )|(p_frag->p_buffer[5] >> 6);
 690             p_sys->i_picture_type = ( p_frag->p_buffer[5] >> 3 ) & 0x03;
 691         }
 692
 693         p_sys->i_dts = p_frag->i_dts;
 694         p_sys->i_pts = p_frag->i_pts;
 695     }
 696     else if( p_frag->p_buffer[3] >= 0x01 && p_frag->p_buffer[3] <= 0xaf )
 697     {
 698         /* Slice start code */
 699         p_sys->b_frame_slice = VLC_TRUE;
 700     }
 701
 702     /* Append the block */
 703     block_ChainLastAppend( &p_sys->pp_last, p_frag );
 704
 705     return p_pic;
 706 }