modules/packetizer/mpegvideo.c

   1 /*****************************************************************************
   2  * mpegvideo.c: parse and packetize an MPEG1/2 video stream
   3  *****************************************************************************
   4  * Copyright (C) 2001-2006 VLC authors and VideoLAN
   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 it
  13  * under the terms of the GNU Lesser General Public License as published by
  14  * the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Lesser General Public License
  23  * along with this program; if not, write to the Free Software Foundation,
  24  * 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 #include "packetizer_helper.h"
  56
  57 #define SYNC_INTRAFRAME_TEXT N_("Sync on Intra Frame")
  58 #define SYNC_INTRAFRAME_LONGTEXT N_("Normally the packetizer would " \
  59     "sync on the next full frame. This flags instructs the packetizer " \
  60     "to sync on the first Intra Frame found.")
  61
  62 /*****************************************************************************
  63  * Module descriptor
  64  *****************************************************************************/
  65 static int  Open ( vlc_object_t * );
  66 static void Close( vlc_object_t * );
  67
  68 vlc_module_begin ()
  69     set_category( CAT_SOUT )
  70     set_subcategory( SUBCAT_SOUT_PACKETIZER )
  71     set_description( N_("MPEG-I/II video packetizer") )
  72     set_shortname( N_("MPEG Video") )
  73     set_capability( "packetizer", 50 )
  74     set_callbacks( Open, Close )
  75
  76     add_bool( "packetizer-mpegvideo-sync-iframe", false, SYNC_INTRAFRAME_TEXT,
  77               SYNC_INTRAFRAME_LONGTEXT, true )
  78 vlc_module_end ()
  79
  80 /*****************************************************************************
  81  * Local prototypes
  82  *****************************************************************************/
  83 struct decoder_sys_t
  84 {
  85     /*
  86      * Input properties
  87      */
  88     packetizer_t packetizer;
  89
  90     /* Sequence header and extension */
  91     block_t *p_seq;
  92     block_t *p_ext;
  93
  94     /* Current frame being built */
  95     block_t    *p_frame;
  96     block_t    **pp_last;
  97
  98     bool b_frame_slice;
  99     mtime_t i_pts;
 100     mtime_t i_dts;
 101
 102     /* Sequence properties */
 103     int         i_frame_rate;
 104     int         i_frame_rate_base;
 105     bool  b_seq_progressive;
 106     bool  b_low_delay;
 107     int         i_aspect_ratio_info;
 108     bool  b_inited;
 109
 110     /* Picture properties */
 111     int i_temporal_ref;
 112     int i_picture_type;
 113     int i_picture_structure;
 114     int i_top_field_first;
 115     int i_repeat_first_field;
 116     int i_progressive_frame;
 117
 118     mtime_t i_interpolated_dts;
 119     mtime_t i_last_ref_pts;
 120     bool b_second_field;
 121
 122     /* Number of pictures since last sequence header */
 123     int i_seq_old;
 124
 125     /* Sync behaviour */
 126     bool  b_sync_on_intra_frame;
 127     bool  b_discontinuity;
 128
 129     /* */
 130     bool b_cc_reset;
 131     uint32_t i_cc_flags;
 132     mtime_t i_cc_pts;
 133     mtime_t i_cc_dts;
 134     cc_data_t cc;
 135 };
 136
 137 static block_t *Packetize( decoder_t *, block_t ** );
 138 static block_t *GetCc( decoder_t *p_dec, bool pb_present[4] );
 139
 140 static void PacketizeReset( void *p_private, bool b_broken );
 141 static block_t *PacketizeParse( void *p_private, bool *pb_ts_used, block_t * );
 142 static int PacketizeValidate( void *p_private, block_t * );
 143
 144 static block_t *ParseMPEGBlock( decoder_t *, block_t * );
 145
 146 static const uint8_t p_mp2v_startcode[3] = { 0x00, 0x00, 0x01 };
 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_CODEC_MPGV )
 157         return VLC_EGENERIC;
 158
 159     es_format_Init( &p_dec->fmt_out, VIDEO_ES, VLC_CODEC_MPGV );
 160     p_dec->fmt_out.i_original_fourcc = p_dec->fmt_in.i_original_fourcc;
 161
 162     p_dec->pf_packetize = Packetize;
 163     p_dec->pf_get_cc = GetCc;
 164
 165     p_dec->p_sys = p_sys = malloc( sizeof( decoder_sys_t ) );
 166     if( !p_dec->p_sys )
 167         return VLC_ENOMEM;
 168     memset( p_dec->p_sys, 0, sizeof( decoder_sys_t ) );
 169
 170     /* Misc init */
 171     packetizer_Init( &p_sys->packetizer,
 172                      p_mp2v_startcode, sizeof(p_mp2v_startcode),
 173                      NULL, 0, 4,
 174                      PacketizeReset, PacketizeParse, PacketizeValidate, p_dec );
 175
 176     p_sys->p_seq = NULL;
 177     p_sys->p_ext = NULL;
 178     p_sys->p_frame = NULL;
 179     p_sys->pp_last = &p_sys->p_frame;
 180     p_sys->b_frame_slice = false;
 181
 182     p_sys->i_dts = p_sys->i_pts = VLC_TS_INVALID;
 183
 184     p_sys->i_frame_rate = 1;
 185     p_sys->i_frame_rate_base = 1;
 186     p_sys->b_seq_progressive = true;
 187     p_sys->b_low_delay = true;
 188     p_sys->i_seq_old = 0;
 189
 190     p_sys->i_temporal_ref = 0;
 191     p_sys->i_picture_type = 0;
 192     p_sys->i_picture_structure = 0x03; /* frame */
 193     p_sys->i_top_field_first = 0;
 194     p_sys->i_repeat_first_field = 0;
 195     p_sys->i_progressive_frame = 0;
 196     p_sys->b_inited = 0;
 197
 198     p_sys->i_interpolated_dts = VLC_TS_INVALID;
 199     p_sys->i_last_ref_pts = VLC_TS_INVALID;
 200     p_sys->b_second_field = 0;
 201
 202     p_sys->b_discontinuity = false;
 203     p_sys->b_sync_on_intra_frame = var_CreateGetBool( p_dec, "packetizer-mpegvideo-sync-iframe" );
 204     if( p_sys->b_sync_on_intra_frame )
 205         msg_Dbg( p_dec, "syncing on intra frame now" );
 206
 207     p_sys->b_cc_reset = false;
 208     p_sys->i_cc_pts = 0;
 209     p_sys->i_cc_dts = 0;
 210     p_sys->i_cc_flags = 0;
 211     cc_Init( &p_sys->cc );
 212
 213     return VLC_SUCCESS;
 214 }
 215
 216 /*****************************************************************************
 217  * Close:
 218  *****************************************************************************/
 219 static void Close( vlc_object_t *p_this )
 220 {
 221     decoder_t     *p_dec = (decoder_t*)p_this;
 222     decoder_sys_t *p_sys = p_dec->p_sys;
 223
 224     if( p_sys->p_seq )
 225     {
 226         block_Release( p_sys->p_seq );
 227     }
 228     if( p_sys->p_ext )
 229     {
 230         block_Release( p_sys->p_ext );
 231     }
 232     if( p_sys->p_frame )
 233     {
 234         block_ChainRelease( p_sys->p_frame );
 235     }
 236     packetizer_Clean( &p_sys->packetizer );
 237
 238     var_Destroy( p_dec, "packetizer-mpegvideo-sync-iframe" );
 239
 240     free( p_sys );
 241 }
 242
 243 /*****************************************************************************
 244  * Packetize:
 245  *****************************************************************************/
 246 static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
 247 {
 248     decoder_sys_t *p_sys = p_dec->p_sys;
 249
 250     return packetizer_Packetize( &p_sys->packetizer, pp_block );
 251 }
 252
 253 /*****************************************************************************
 254  * GetCc:
 255  *****************************************************************************/
 256 static block_t *GetCc( decoder_t *p_dec, bool pb_present[4] )
 257 {
 258     decoder_sys_t *p_sys = p_dec->p_sys;
 259     block_t *p_cc;
 260     int i;
 261
 262     for( i = 0; i < 4; i++ )
 263         pb_present[i] = p_sys->cc.pb_present[i];
 264
 265     if( p_sys->cc.i_data <= 0 )
 266         return NULL;
 267
 268     p_cc = block_Alloc( p_sys->cc.i_data );
 269     if( p_cc )
 270     {
 271         memcpy( p_cc->p_buffer, p_sys->cc.p_data, p_sys->cc.i_data );
 272         p_cc->i_dts =
 273         p_cc->i_pts = p_sys->cc.b_reorder ? p_sys->i_cc_pts : p_sys->i_cc_dts;
 274         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);
 275     }
 276     cc_Flush( &p_sys->cc );
 277     return p_cc;
 278 }
 279
 280 /*****************************************************************************
 281  * Helpers:
 282  *****************************************************************************/
 283 static void PacketizeReset( void *p_private, bool b_broken )
 284 {
 285     decoder_t *p_dec = p_private;
 286     decoder_sys_t *p_sys = p_dec->p_sys;
 287
 288     if( b_broken )
 289     {
 290         p_sys->b_discontinuity = true;
 291         if( p_sys->p_frame )
 292             block_ChainRelease( p_sys->p_frame );
 293         p_sys->p_frame = NULL;
 294         p_sys->pp_last = &p_sys->p_frame;
 295         p_sys->b_frame_slice = false;
 296     }
 297     p_sys->i_dts =
 298     p_sys->i_pts =
 299     p_sys->i_interpolated_dts =
 300     p_sys->i_last_ref_pts = VLC_TS_INVALID;
 301 }
 302
 303 static block_t *PacketizeParse( void *p_private, bool *pb_ts_used, block_t *p_block )
 304 {
 305     decoder_t *p_dec = p_private;
 306
 307     /* Check if we have a picture start code */
 308     *pb_ts_used = p_block->p_buffer[3] == 0x00;
 309
 310     return ParseMPEGBlock( p_dec, p_block );
 311 }
 312
 313
 314 static int PacketizeValidate( void *p_private, block_t *p_au )
 315 {
 316     decoder_t *p_dec = p_private;
 317     decoder_sys_t *p_sys = p_dec->p_sys;
 318
 319     /* If a discontinuity has been encountered, then wait till
 320      * the next Intra frame before continuing with packetizing */
 321     if( p_sys->b_discontinuity &&
 322         p_sys->b_sync_on_intra_frame )
 323     {
 324         if( (p_au->i_flags & BLOCK_FLAG_TYPE_I) == 0 )
 325         {
 326             msg_Dbg( p_dec, "waiting on intra frame" );
 327             return VLC_EGENERIC;
 328         }
 329         msg_Dbg( p_dec, "synced on intra frame" );
 330         p_sys->b_discontinuity = false;
 331         p_au->i_flags |= BLOCK_FLAG_DISCONTINUITY;
 332     }
 333
 334     /* We've just started the stream, wait for the first PTS.
 335      * We discard here so we can still get the sequence header. */
 336     if( p_sys->i_dts <= VLC_TS_INVALID && p_sys->i_pts <= VLC_TS_INVALID &&
 337         p_sys->i_interpolated_dts <= VLC_TS_INVALID )
 338     {
 339         msg_Dbg( p_dec, "need a starting pts/dts" );
 340         return VLC_EGENERIC;
 341     }
 342
 343     /* When starting the stream we can have the first frame with
 344      * an invalid DTS (i_interpolated_pts is initialized to VLC_TS_INVALID) */
 345     if( p_au->i_dts <= VLC_TS_INVALID )
 346         p_au->i_dts = p_au->i_pts;
 347
 348     return VLC_SUCCESS;
 349 }
 350 /*****************************************************************************
 351  * ParseMPEGBlock: Re-assemble fragments into a block containing a picture
 352  *****************************************************************************/
 353 static block_t *ParseMPEGBlock( decoder_t *p_dec, block_t *p_frag )
 354 {
 355     decoder_sys_t *p_sys = p_dec->p_sys;
 356     block_t *p_pic = NULL;
 357
 358     /*
 359      * Check if previous picture is finished
 360      */
 361     if( ( p_sys->b_frame_slice &&
 362           (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) ) &&
 363           p_sys->p_seq == NULL )
 364     {
 365         /* We have a picture but without a sequence header we can't
 366          * do anything */
 367         msg_Dbg( p_dec, "waiting for sequence start" );
 368         if( p_sys->p_frame ) block_ChainRelease( p_sys->p_frame );
 369         p_sys->p_frame = NULL;
 370         p_sys->pp_last = &p_sys->p_frame;
 371         p_sys->b_frame_slice = false;
 372
 373     }
 374     else if( p_sys->b_frame_slice &&
 375              (p_frag->p_buffer[3] == 0x00 || p_frag->p_buffer[3] > 0xaf) )
 376     {
 377         const bool b_eos = p_frag->p_buffer[3] == 0xb7;
 378
 379         mtime_t i_duration;
 380
 381         if( b_eos )
 382         {
 383             block_ChainLastAppend( &p_sys->pp_last, p_frag );
 384             p_frag = NULL;
 385         }
 386
 387         p_pic = block_ChainGather( p_sys->p_frame );
 388
 389         if( b_eos )
 390             p_pic->i_flags |= BLOCK_FLAG_END_OF_SEQUENCE;
 391
 392         i_duration = (mtime_t)( CLOCK_FREQ * p_sys->i_frame_rate_base /
 393                                 p_sys->i_frame_rate );
 394
 395         if( !p_sys->b_seq_progressive && p_sys->i_picture_structure != 0x03 )
 396         {
 397             i_duration /= 2;
 398         }
 399
 400         if( p_sys->b_seq_progressive )
 401         {
 402             if( p_sys->i_top_field_first == 0 &&
 403                 p_sys->i_repeat_first_field == 1 )
 404             {
 405                 i_duration *= 2;
 406             }
 407             else if( p_sys->i_top_field_first == 1 &&
 408                      p_sys->i_repeat_first_field == 1 )
 409             {
 410                 i_duration *= 3;
 411             }
 412         }
 413         else
 414         {
 415             if( p_sys->i_picture_structure == 0x03 )
 416             {
 417                 if( p_sys->i_progressive_frame && p_sys->i_repeat_first_field )
 418                 {
 419                     i_duration += i_duration / 2;
 420                 }
 421             }
 422         }
 423
 424         if( p_sys->b_low_delay || p_sys->i_picture_type == 0x03 )
 425         {
 426             /* Trivial case (DTS == PTS) */
 427             /* Correct interpolated dts when we receive a new pts/dts */
 428             if( p_sys->i_pts > VLC_TS_INVALID )
 429                 p_sys->i_interpolated_dts = p_sys->i_pts;
 430             if( p_sys->i_dts > VLC_TS_INVALID )
 431                 p_sys->i_interpolated_dts = p_sys->i_dts;
 432         }
 433         else
 434         {
 435             /* Correct interpolated dts when we receive a new pts/dts */
 436             if(p_sys->i_last_ref_pts > VLC_TS_INVALID && !p_sys->b_second_field)
 437                 p_sys->i_interpolated_dts = p_sys->i_last_ref_pts;
 438             if( p_sys->i_dts > VLC_TS_INVALID )
 439                 p_sys->i_interpolated_dts = p_sys->i_dts;
 440
 441             if( !p_sys->b_second_field )
 442                 p_sys->i_last_ref_pts = p_sys->i_pts;
 443         }
 444
 445         p_pic->i_dts = p_sys->i_interpolated_dts;
 446         p_sys->i_interpolated_dts += i_duration;
 447
 448         /* Set PTS only if we have a B frame or if it comes from the stream */
 449         if( p_sys->i_pts > VLC_TS_INVALID )
 450         {
 451             p_pic->i_pts = p_sys->i_pts;
 452         }
 453         else if( p_sys->i_picture_type == 0x03 )
 454         {
 455             p_pic->i_pts = p_pic->i_dts;
 456         }
 457         else
 458         {
 459             p_pic->i_pts = VLC_TS_INVALID;
 460         }
 461
 462         switch ( p_sys->i_picture_type )
 463         {
 464         case 0x01:
 465             p_pic->i_flags |= BLOCK_FLAG_TYPE_I;
 466             break;
 467         case 0x02:
 468             p_pic->i_flags |= BLOCK_FLAG_TYPE_P;
 469             break;
 470         case 0x03:
 471             p_pic->i_flags |= BLOCK_FLAG_TYPE_B;
 472             break;
 473         }
 474
 475         p_pic->i_length = p_sys->i_interpolated_dts - p_pic->i_dts;
 476
 477 #if 0
 478         msg_Dbg( p_dec, "pic: type=%d dts=%"PRId64" pts-dts=%"PRId64,
 479         p_sys->i_picture_type, p_pic->i_dts, p_pic->i_pts - p_pic->i_dts);
 480 #endif
 481
 482         /* Reset context */
 483         p_sys->p_frame = NULL;
 484         p_sys->pp_last = &p_sys->p_frame;
 485         p_sys->b_frame_slice = false;
 486
 487         if( p_sys->i_picture_structure != 0x03 )
 488         {
 489             p_sys->b_second_field = !p_sys->b_second_field;
 490         }
 491         else
 492         {
 493             p_sys->b_second_field = 0;
 494         }
 495
 496         /* CC */
 497         p_sys->b_cc_reset = true;
 498         p_sys->i_cc_pts = p_pic->i_pts;
 499         p_sys->i_cc_dts = p_pic->i_dts;
 500         p_sys->i_cc_flags = p_pic->i_flags;
 501     }
 502
 503     if( !p_pic && p_sys->b_cc_reset )
 504     {
 505         p_sys->b_cc_reset = false;
 506         cc_Flush( &p_sys->cc );
 507     }
 508
 509     if( !p_frag )
 510         return p_pic;
 511     /*
 512      * Check info of current fragment
 513      */
 514     if( p_frag->p_buffer[3] == 0xb8 )
 515     {
 516         /* Group start code */
 517         if( p_sys->p_seq &&
 518             p_sys->i_seq_old > p_sys->i_frame_rate/p_sys->i_frame_rate_base )
 519         {
 520             /* Useful for mpeg1: repeat sequence header every second */
 521             block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_seq ) );
 522             if( p_sys->p_ext )
 523             {
 524                 block_ChainLastAppend( &p_sys->pp_last, block_Duplicate( p_sys->p_ext ) );
 525             }
 526
 527             p_sys->i_seq_old = 0;
 528         }
 529     }
 530     else if( p_frag->p_buffer[3] == 0xb3 && p_frag->i_buffer >= 8 )
 531     {
 532         /* Sequence header code */
 533         static const int code_to_frame_rate[16][2] =
 534         {
 535             { 1, 1 },  /* invalid */
 536             { 24000, 1001 }, { 24, 1 }, { 25, 1 },       { 30000, 1001 },
 537             { 30, 1 },       { 50, 1 }, { 60000, 1001 }, { 60, 1 },
 538             /* Unofficial 15fps from Xing*/
 539             { 15, 1001 },
 540             /* Unofficial economy rates from libmpeg3 */
 541             { 5000, 1001 }, { 1000, 1001 }, { 12000, 1001 }, { 15000, 1001 },
 542             { 1, 1 },  { 1, 1 }  /* invalid */
 543         };
 544
 545         if( p_sys->p_seq ) block_Release( p_sys->p_seq );
 546         if( p_sys->p_ext ) block_Release( p_sys->p_ext );
 547
 548         p_sys->p_seq = block_Duplicate( p_frag );
 549         p_sys->i_seq_old = 0;
 550         p_sys->p_ext = NULL;
 551
 552         p_dec->fmt_out.video.i_width =
 553             ( p_frag->p_buffer[4] << 4)|(p_frag->p_buffer[5] >> 4 );
 554         p_dec->fmt_out.video.i_height =
 555             ( (p_frag->p_buffer[5]&0x0f) << 8 )|p_frag->p_buffer[6];
 556         p_sys->i_aspect_ratio_info = p_frag->p_buffer[7] >> 4;
 557
 558         /* TODO: MPEG1 aspect ratio */
 559
 560         p_sys->i_frame_rate = code_to_frame_rate[p_frag->p_buffer[7]&0x0f][0];
 561         p_sys->i_frame_rate_base =
 562             code_to_frame_rate[p_frag->p_buffer[7]&0x0f][1];
 563
 564         p_dec->fmt_out.video.i_frame_rate = p_sys->i_frame_rate;
 565         p_dec->fmt_out.video.i_frame_rate_base = p_sys->i_frame_rate_base;
 566
 567         p_sys->b_seq_progressive = true;
 568         p_sys->b_low_delay = true;
 569
 570         if ( !p_sys->b_inited )
 571         {
 572             msg_Dbg( p_dec, "size %dx%d fps=%.3f",
 573                  p_dec->fmt_out.video.i_width, p_dec->fmt_out.video.i_height,
 574                  p_sys->i_frame_rate / (float)p_sys->i_frame_rate_base );
 575             p_sys->b_inited = 1;
 576         }
 577     }
 578     else if( p_frag->p_buffer[3] == 0xb5 )
 579     {
 580         int i_type = p_frag->p_buffer[4] >> 4;
 581
 582         /* Extension start code */
 583         if( i_type == 0x01 )
 584         {
 585 #if 0
 586             static const int mpeg2_aspect[16][2] =
 587             {
 588                 {0,1}, {1,1}, {4,3}, {16,9}, {221,100},
 589                 {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1}, {0,1},
 590                 {0,1}, {0,1}
 591             };
 592 #endif
 593
 594             /* sequence extension */
 595             if( p_sys->p_ext) block_Release( p_sys->p_ext );
 596             p_sys->p_ext = block_Duplicate( p_frag );
 597
 598             if( p_frag->i_buffer >= 10 )
 599             {
 600                 p_sys->b_seq_progressive =
 601                     p_frag->p_buffer[5]&0x08 ? true : false;
 602                 p_sys->b_low_delay =
 603                     p_frag->p_buffer[9]&0x80 ? true : false;
 604             }
 605
 606             /* Do not set aspect ratio : in case we're transcoding,
 607              * transcode will take our fmt_out as a fmt_in to libmpeg2.
 608              * libmpeg2.c will then believe that the user has requested
 609              * a specific aspect ratio, which she hasn't. Thus in case
 610              * of aspect ratio change, we're screwed. --Meuuh
 611              */
 612 #if 0
 613             p_dec->fmt_out.video.i_sar_num =
 614                 mpeg2_aspect[p_sys->i_aspect_ratio_info][0] *
 615                 p_dec->fmt_out.video.i_height;
 616             p_dec->fmt_out.video.i_sar_den =
 617                 mpeg2_aspect[p_sys->i_aspect_ratio_info][1] *
 618                 p_dec->fmt_out.video.i_width;
 619 #endif
 620
 621         }
 622         else if( i_type == 0x08 )
 623         {
 624             /* picture extension */
 625             p_sys->i_picture_structure = p_frag->p_buffer[6]&0x03;
 626             p_sys->i_top_field_first   = p_frag->p_buffer[7] >> 7;
 627             p_sys->i_repeat_first_field= (p_frag->p_buffer[7]>>1)&0x01;
 628             p_sys->i_progressive_frame = p_frag->p_buffer[8] >> 7;
 629         }
 630     }
 631     else if( p_frag->p_buffer[3] == 0xb2 && p_frag->i_buffer > 4 )
 632     {
 633         cc_Extract( &p_sys->cc, p_sys->i_top_field_first,
 634                     &p_frag->p_buffer[4], p_frag->i_buffer - 4 );
 635     }
 636     else if( p_frag->p_buffer[3] == 0x00 )
 637     {
 638         /* Picture start code */
 639         p_sys->i_seq_old++;
 640
 641         if( p_frag->i_buffer >= 6 )
 642         {
 643             p_sys->i_temporal_ref =
 644                 ( p_frag->p_buffer[4] << 2 )|(p_frag->p_buffer[5] >> 6);
 645             p_sys->i_picture_type = ( p_frag->p_buffer[5] >> 3 ) & 0x03;
 646         }
 647
 648         p_sys->i_dts = p_frag->i_dts;
 649         p_sys->i_pts = p_frag->i_pts;
 650     }
 651     else if( p_frag->p_buffer[3] >= 0x01 && p_frag->p_buffer[3] <= 0xaf )
 652     {
 653         /* Slice start code */
 654         p_sys->b_frame_slice = true;
 655     }
 656
 657     /* Append the block */
 658     block_ChainLastAppend( &p_sys->pp_last, p_frag );
 659
 660     return p_pic;
 661 }