git.sesse.net Git - vlc/blob - modules/packetizer/mpeg4video.c

   1 /*****************************************************************************
   2  * mpeg4video.c: mpeg 4 video packetizer
   3  *****************************************************************************
   4  * Copyright (C) 2001-2006 the VideoLAN team
   5  * $Id$
   6  *
   7  * Authors: Gildas Bazin <gbazin@videolan.org>
   8  *          Laurent Aimar <fenrir@via.ecp.fr>
   9  *          Eric Petit <titer@videolan.org>
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License as published by
  13  * the Free Software Foundation; either version 2 of the License, or
  14  * (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  24  *****************************************************************************/
  25
  26 /*****************************************************************************
  27  * Preamble
  28  *****************************************************************************/
  29 #include <stdlib.h>                                      /* malloc(), free() */
  30
  31 #include <vlc/vlc.h>
  32 #include <vlc_sout.h>
  33 #include <vlc_codec.h>
  34 #include <vlc_block.h>
  35 #include <vlc_input.h>                  /* hmmm, just for INPUT_RATE_DEFAULT */
  36
  37 #include "vlc_bits.h"
  38 #include "vlc_block_helper.h"
  39
  40 /*****************************************************************************
  41  * Module descriptor
  42  *****************************************************************************/
  43 static int  Open ( vlc_object_t * );
  44 static void Close( vlc_object_t * );
  45
  46 vlc_module_begin();
  47     set_category( CAT_SOUT );
  48     set_subcategory( SUBCAT_SOUT_PACKETIZER );
  49     set_description( _("MPEG4 video packetizer") );
  50     set_capability( "packetizer", 50 );
  51     set_callbacks( Open, Close );
  52 vlc_module_end();
  53
  54 /****************************************************************************
  55  * Local prototypes
  56  ****************************************************************************/
  57 static block_t *Packetize( decoder_t *, block_t ** );
  58
  59 struct decoder_sys_t
  60 {
  61     /*
  62      * Input properties
  63      */
  64     block_bytestream_t bytestream;
  65     int i_state;
  66     int i_offset;
  67     uint8_t p_startcode[3];
  68
  69     /*
  70      * Common properties
  71      */
  72     mtime_t i_interpolated_pts;
  73     mtime_t i_interpolated_dts;
  74     mtime_t i_last_ref_pts;
  75     mtime_t i_last_time_ref;
  76     mtime_t i_time_ref;
  77     mtime_t i_last_time;
  78     mtime_t i_last_timeincr;
  79
  80     unsigned int i_flags;
  81
  82     int         i_fps_num;
  83     int         i_fps_den;
  84     int         i_last_incr;
  85     int         i_last_incr_diff;
  86
  87     vlc_bool_t  b_frame;
  88
  89     /* Current frame being built */
  90     block_t    *p_frame;
  91     block_t    **pp_last;
  92 };
  93
  94 enum {
  95     STATE_NOSYNC,
  96     STATE_NEXT_SYNC
  97 };
  98
  99 static block_t *ParseMPEGBlock( decoder_t *, block_t * );
 100 static int ParseVOL( decoder_t *, es_format_t *, uint8_t *, int );
 101 static int ParseVOP( decoder_t *, block_t * );
 102 static int vlc_log2( unsigned int );
 103
 104 #define VIDEO_OBJECT_MASK                       0x01f
 105 #define VIDEO_OBJECT_LAYER_MASK                 0x00f
 106
 107 #define VIDEO_OBJECT_START_CODE                 0x100
 108 #define VIDEO_OBJECT_LAYER_START_CODE           0x120
 109 #define VISUAL_OBJECT_SEQUENCE_START_CODE       0x1b0
 110 #define VISUAL_OBJECT_SEQUENCE_END_CODE         0x1b1
 111 #define USER_DATA_START_CODE                    0x1b2
 112 #define GROUP_OF_VOP_START_CODE                 0x1b3
 113 #define VIDEO_SESSION_ERROR_CODE                0x1b4
 114 #define VISUAL_OBJECT_START_CODE                0x1b5
 115 #define VOP_START_CODE                          0x1b6
 116 #define FACE_OBJECT_START_CODE                  0x1ba
 117 #define FACE_OBJECT_PLANE_START_CODE            0x1bb
 118 #define MESH_OBJECT_START_CODE                  0x1bc
 119 #define MESH_OBJECT_PLANE_START_CODE            0x1bd
 120 #define STILL_TEXTURE_OBJECT_START_CODE         0x1be
 121 #define TEXTURE_SPATIAL_LAYER_START_CODE        0x1bf
 122 #define TEXTURE_SNR_LAYER_START_CODE            0x1c0
 123
 124 /*****************************************************************************
 125  * Open: probe the packetizer and return score
 126  *****************************************************************************/
 127 static int Open( vlc_object_t *p_this )
 128 {
 129     decoder_t     *p_dec = (decoder_t*)p_this;
 130     decoder_sys_t *p_sys;
 131
 132     switch( p_dec->fmt_in.i_codec )
 133     {
 134         case VLC_FOURCC( 'm', '4', 's', '2'):
 135         case VLC_FOURCC( 'M', '4', 'S', '2'):
 136         case VLC_FOURCC( 'm', 'p', '4', 's'):
 137         case VLC_FOURCC( 'M', 'P', '4', 'S'):
 138         case VLC_FOURCC( 'm', 'p', '4', 'v'):
 139         case VLC_FOURCC( 'M', 'P', '4', 'V'):
 140         case VLC_FOURCC( 'D', 'I', 'V', 'X'):
 141         case VLC_FOURCC( 'd', 'i', 'v', 'x'):
 142         case VLC_FOURCC( 'X', 'V', 'I', 'D'):
 143         case VLC_FOURCC( 'X', 'v', 'i', 'D'):
 144         case VLC_FOURCC( 'x', 'v', 'i', 'd'):
 145         case VLC_FOURCC( 'D', 'X', '5', '0'):
 146         case VLC_FOURCC( 'd', 'x', '5', '0'):
 147         case VLC_FOURCC( 0x04, 0,   0,   0):
 148         case VLC_FOURCC( '3', 'I', 'V', '2'):
 149         case VLC_FOURCC( 'm', '4', 'c', 'c'):
 150         case VLC_FOURCC( 'M', '4', 'C', 'C'):
 151             break;
 152
 153         default:
 154             return VLC_EGENERIC;
 155     }
 156
 157     /* Allocate the memory needed to store the decoder's structure */
 158     if( ( p_dec->p_sys = p_sys = malloc( sizeof(decoder_sys_t) ) ) == NULL )
 159     {
 160         msg_Err( p_dec, "out of memory" );
 161         return VLC_EGENERIC;
 162     }
 163     memset( p_sys, 0, sizeof(decoder_sys_t) );
 164
 165     /* Misc init */
 166     p_sys->i_state = STATE_NOSYNC;
 167     p_sys->bytestream = block_BytestreamInit( p_dec );
 168     p_sys->p_startcode[0] = 0;
 169     p_sys->p_startcode[1] = 0;
 170     p_sys->p_startcode[2] = 1;
 171     p_sys->i_offset = 0;
 172     p_sys->p_frame = NULL;
 173     p_sys->pp_last = &p_sys->p_frame;
 174
 175     /* Setup properties */
 176     es_format_Copy( &p_dec->fmt_out, &p_dec->fmt_in );
 177     p_dec->fmt_out.i_codec = VLC_FOURCC( 'm', 'p', '4', 'v' );
 178
 179     if( p_dec->fmt_in.i_extra )
 180     {
 181         /* We have a vol */
 182         p_dec->fmt_out.i_extra = p_dec->fmt_in.i_extra;
 183         p_dec->fmt_out.p_extra = malloc( p_dec->fmt_in.i_extra );
 184         memcpy( p_dec->fmt_out.p_extra, p_dec->fmt_in.p_extra,
 185                 p_dec->fmt_in.i_extra );
 186
 187         msg_Dbg( p_dec, "opening with vol size: %d", p_dec->fmt_in.i_extra );
 188         ParseVOL( p_dec, &p_dec->fmt_out,
 189                   p_dec->fmt_out.p_extra, p_dec->fmt_out.i_extra );
 190     }
 191     else
 192     {
 193         /* No vol, we'll have to look for one later on */
 194         p_dec->fmt_out.i_extra = 0;
 195         p_dec->fmt_out.p_extra = 0;
 196     }
 197
 198     /* Set callback */
 199     p_dec->pf_packetize = Packetize;
 200
 201     return VLC_SUCCESS;
 202 }
 203
 204 /*****************************************************************************
 205  * Close: clean up the packetizer
 206  *****************************************************************************/
 207 static void Close( vlc_object_t *p_this )
 208 {
 209     decoder_t *p_dec = (decoder_t*)p_this;
 210
 211     block_BytestreamRelease( &p_dec->p_sys->bytestream );
 212     if( p_dec->p_sys->p_frame ) block_ChainRelease( p_dec->p_sys->p_frame );
 213     free( p_dec->p_sys );
 214 }
 215
 216 /****************************************************************************
 217  * Packetize: the whole thing
 218  ****************************************************************************/
 219 static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
 220 {
 221     decoder_sys_t *p_sys = p_dec->p_sys;
 222     block_t       *p_pic;
 223     mtime_t       i_pts, i_dts;
 224
 225     if( pp_block == NULL || *pp_block == NULL ) return NULL;
 226
 227     if( (*pp_block)->i_flags&(BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 228     {
 229         if( (*pp_block)->i_flags&BLOCK_FLAG_CORRUPTED )
 230         {
 231             p_sys->i_state = STATE_NOSYNC;
 232             block_BytestreamFlush( &p_sys->bytestream );
 233
 234             if( p_sys->p_frame )
 235                 block_ChainRelease( p_sys->p_frame );
 236             p_sys->p_frame = NULL;
 237             p_sys->pp_last = &p_sys->p_frame;
 238         }
 239 //        p_sys->i_interpolated_pts =
 240 //        p_sys->i_interpolated_dts =
 241 //        p_sys->i_last_ref_pts =
 242 //        p_sys->i_last_time_ref =
 243 //        p_sys->i_time_ref =
 244 //        p_sys->i_last_time =
 245 //        p_sys->i_last_timeincr = 0;
 246
 247         block_Release( *pp_block );
 248         return NULL;
 249     }
 250
 251     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 252
 253     while( 1 )
 254     {
 255         switch( p_sys->i_state )
 256         {
 257
 258         case STATE_NOSYNC:
 259             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 260                     &p_sys->i_offset, p_sys->p_startcode, 3 ) == VLC_SUCCESS )
 261             {
 262                 p_sys->i_state = STATE_NEXT_SYNC;
 263             }
 264
 265             if( p_sys->i_offset )
 266             {
 267                 block_SkipBytes( &p_sys->bytestream, p_sys->i_offset );
 268                 p_sys->i_offset = 0;
 269                 block_BytestreamFlush( &p_sys->bytestream );
 270             }
 271
 272             if( p_sys->i_state != STATE_NEXT_SYNC )
 273             {
 274                 /* Need more data */
 275                 return NULL;
 276             }
 277
 278             p_sys->i_offset = 1; /* To find next startcode */
 279
 280         case STATE_NEXT_SYNC:
 281             /* TODO: If p_block == NULL, flush the buffer without checking the
 282              * next sync word */
 283
 284             /* Find the next startcode */
 285             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 286                     &p_sys->i_offset, p_sys->p_startcode, 3 ) != VLC_SUCCESS )
 287             {
 288                 /* Need more data */
 289                 return NULL;
 290             }
 291
 292             /* Get the new fragment and set the pts/dts */
 293             p_pic = block_New( p_dec, p_sys->i_offset );
 294             block_BytestreamFlush( &p_sys->bytestream );
 295             p_pic->i_pts = i_pts = p_sys->bytestream.p_block->i_pts;
 296             p_pic->i_dts = i_dts = p_sys->bytestream.p_block->i_dts;
 297             p_pic->i_rate = p_sys->bytestream.p_block->i_rate;
 298
 299             block_GetBytes( &p_sys->bytestream, p_pic->p_buffer,
 300                             p_pic->i_buffer );
 301
 302             p_sys->i_offset = 0;
 303
 304             /* Get picture if any */
 305             if( !( p_pic = ParseMPEGBlock( p_dec, p_pic ) ) )
 306             {
 307                 p_sys->i_state = STATE_NOSYNC;
 308                 break;
 309             }
 310
 311             /* don't reuse the same timestamps several times */
 312             if( i_pts == p_sys->bytestream.p_block->i_pts &&
 313                 i_dts == p_sys->bytestream.p_block->i_dts )
 314             {
 315                 p_sys->bytestream.p_block->i_pts = 0;
 316                 p_sys->bytestream.p_block->i_dts = 0;
 317             }
 318
 319             /* We've just started the stream, wait for the first PTS.
 320              * We discard here so we can still get the sequence header. */
 321             if( p_sys->i_interpolated_pts <= 0 &&
 322                 p_sys->i_interpolated_dts <= 0 )
 323             {
 324                 msg_Dbg( p_dec, "need a starting pts/dts" );
 325                 p_sys->i_state = STATE_NOSYNC;
 326                 block_Release( p_pic );
 327                 break;
 328             }
 329
 330             /* When starting the stream we can have the first frame with
 331              * a null DTS (i_interpolated_pts is initialized to 0) */
 332             if( !p_pic->i_dts ) p_pic->i_dts = p_pic->i_pts;
 333
 334             /* So p_block doesn't get re-added several times */
 335             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 336
 337             p_sys->i_state = STATE_NOSYNC;
 338
 339             return p_pic;
 340         }
 341     }
 342 }
 343
 344 /*****************************************************************************
 345  * ParseMPEGBlock: Re-assemble fragments into a block containing a picture
 346  *****************************************************************************/
 347 static block_t *ParseMPEGBlock( decoder_t *p_dec, block_t *p_frag )
 348 {
 349     decoder_sys_t *p_sys = p_dec->p_sys;
 350     block_t *p_pic = NULL;
 351
 352     if( p_frag->p_buffer[3] == 0xB0 || p_frag->p_buffer[3] == 0xB1 || p_frag->p_buffer[3] == 0xB2 )
 353     {   /* VOS and USERDATA */
 354 #if 0
 355         /* Remove VOS start/end code from the original stream */
 356         block_Release( p_frag );
 357 #else
 358         /* Append the block for now since ts/ps muxers rely on VOL
 359          * being present in the stream */
 360         block_ChainLastAppend( &p_sys->pp_last, p_frag );
 361 #endif
 362         return NULL;
 363     }
 364     if( p_frag->p_buffer[3] >= 0x20 && p_frag->p_buffer[3] <= 0x2f )
 365     {
 366         /* Copy the complete VOL */
 367         if( p_dec->fmt_out.i_extra != p_frag->i_buffer )
 368         {
 369             p_dec->fmt_out.p_extra =
 370                 realloc( p_dec->fmt_out.p_extra, p_frag->i_buffer );
 371             p_dec->fmt_out.i_extra = p_frag->i_buffer;
 372         }
 373         memcpy( p_dec->fmt_out.p_extra, p_frag->p_buffer, p_frag->i_buffer );
 374         ParseVOL( p_dec, &p_dec->fmt_out,
 375                   p_dec->fmt_out.p_extra, p_dec->fmt_out.i_extra );
 376
 377 #if 0
 378         /* Remove from the original stream */
 379         block_Release( p_frag );
 380 #else
 381         /* Append the block for now since ts/ps muxers rely on VOL
 382          * being present in the stream */
 383         block_ChainLastAppend( &p_sys->pp_last, p_frag );
 384 #endif
 385         return NULL;
 386     }
 387     else
 388     {
 389         if( !p_dec->fmt_out.i_extra )
 390         {
 391             msg_Warn( p_dec, "waiting for VOL" );
 392             block_Release( p_frag );
 393             return NULL;
 394         }
 395
 396         /* Append the block */
 397         block_ChainLastAppend( &p_sys->pp_last, p_frag );
 398     }
 399
 400     if( p_frag->p_buffer[3] == 0xb6 &&
 401         ParseVOP( p_dec, p_frag ) == VLC_SUCCESS )
 402     {
 403         /* We are dealing with a VOP */
 404         p_pic = block_ChainGather( p_sys->p_frame );
 405         p_pic->i_pts = p_sys->i_interpolated_pts;
 406         p_pic->i_dts = p_sys->i_interpolated_dts;
 407
 408         /* Reset context */
 409         p_sys->p_frame = NULL;
 410         p_sys->pp_last = &p_sys->p_frame;
 411     }
 412
 413     return p_pic;
 414 }
 415
 416 /* ParseVOL:
 417  *  TODO:
 418  *      - support aspect ratio
 419  */
 420 static int ParseVOL( decoder_t *p_dec, es_format_t *fmt,
 421                      uint8_t *p_vol, int i_vol )
 422 {
 423     decoder_sys_t *p_sys = p_dec->p_sys;
 424     int i_vo_type, i_vo_ver_id, i_ar, i_shape;
 425     bs_t s;
 426
 427     for( ;; )
 428     {
 429         if( p_vol[0] == 0x00 && p_vol[1] == 0x00 && p_vol[2] == 0x01 &&
 430             p_vol[3] >= 0x20 && p_vol[3] <= 0x2f ) break;
 431
 432         p_vol++; i_vol--;
 433         if( i_vol <= 4 ) return VLC_EGENERIC;
 434     }
 435
 436     bs_init( &s, &p_vol[4], i_vol - 4 );
 437
 438     bs_skip( &s, 1 );   /* random access */
 439     i_vo_type = bs_read( &s, 8 );
 440     if( bs_read1( &s ) )
 441     {
 442         i_vo_ver_id = bs_read( &s, 4 );
 443         bs_skip( &s, 3 );
 444     }
 445     else
 446     {
 447         i_vo_ver_id = 1;
 448     }
 449     i_ar = bs_read( &s, 4 );
 450     if( i_ar == 0xf )
 451     {
 452         int i_ar_width, i_ar_height;
 453
 454         i_ar_width = bs_read( &s, 8 );
 455         i_ar_height= bs_read( &s, 8 );
 456     }
 457     if( bs_read1( &s ) )
 458     {
 459         int i_chroma_format;
 460         int i_low_delay;
 461
 462         /* vol control parameter */
 463         i_chroma_format = bs_read( &s, 2 );
 464         i_low_delay = bs_read1( &s );
 465
 466         if( bs_read1( &s ) )
 467         {
 468             bs_skip( &s, 16 );
 469             bs_skip( &s, 16 );
 470             bs_skip( &s, 16 );
 471             bs_skip( &s, 3 );
 472             bs_skip( &s, 11 );
 473             bs_skip( &s, 1 );
 474             bs_skip( &s, 16 );
 475         }
 476     }
 477     /* shape 0->RECT, 1->BIN, 2->BIN_ONLY, 3->GRAY */
 478     i_shape = bs_read( &s, 2 );
 479     if( i_shape == 3 && i_vo_ver_id != 1 )
 480     {
 481         bs_skip( &s, 4 );
 482     }
 483
 484     if( !bs_read1( &s ) ) return VLC_EGENERIC; /* Marker */
 485
 486     p_sys->i_fps_num = bs_read( &s, 16 ); /* Time increment resolution*/
 487     if( !p_sys->i_fps_num ) p_sys->i_fps_num = 1;
 488
 489     if( !bs_read1( &s ) ) return VLC_EGENERIC; /* Marker */
 490
 491     if( bs_read1( &s ) )
 492     {
 493         int i_time_increment_bits = vlc_log2( p_sys->i_fps_num - 1 ) + 1;
 494
 495         if( i_time_increment_bits < 1 ) i_time_increment_bits = 1;
 496
 497         p_sys->i_fps_den = bs_read( &s, i_time_increment_bits );
 498     }
 499     if( i_shape == 0 )
 500     {
 501         bs_skip( &s, 1 );
 502         fmt->video.i_width = bs_read( &s, 13 );
 503         bs_skip( &s, 1 );
 504         fmt->video.i_height= bs_read( &s, 13 );
 505         bs_skip( &s, 1 );
 506     }
 507
 508     return VLC_SUCCESS;
 509 }
 510
 511 static int ParseVOP( decoder_t *p_dec, block_t *p_vop )
 512 {
 513     decoder_sys_t *p_sys = p_dec->p_sys;
 514     int64_t i_time_increment, i_time_ref;
 515     int i_modulo_time_base = 0, i_time_increment_bits;
 516     bs_t s;
 517
 518     bs_init( &s, &p_vop->p_buffer[4], p_vop->i_buffer - 4 );
 519
 520     switch( bs_read( &s, 2 ) )
 521     {
 522     case 0:
 523         p_sys->i_flags = BLOCK_FLAG_TYPE_I;
 524         break;
 525     case 1:
 526         p_sys->i_flags = BLOCK_FLAG_TYPE_P;
 527         break;
 528     case 2:
 529         p_sys->i_flags = BLOCK_FLAG_TYPE_B;
 530         p_sys->b_frame = VLC_TRUE;
 531         break;
 532     case 3: /* gni ? */
 533         p_sys->i_flags = BLOCK_FLAG_TYPE_PB;
 534         break;
 535     }
 536
 537     while( bs_read( &s, 1 ) ) i_modulo_time_base++;
 538     if( !bs_read1( &s ) ) return VLC_EGENERIC; /* Marker */
 539
 540     /* VOP time increment */
 541     i_time_increment_bits = vlc_log2(p_dec->p_sys->i_fps_num - 1) + 1;
 542     if( i_time_increment_bits < 1 ) i_time_increment_bits = 1;
 543     i_time_increment = bs_read( &s, i_time_increment_bits );
 544
 545     /* Interpolate PTS/DTS */
 546     if( !(p_sys->i_flags & BLOCK_FLAG_TYPE_B) )
 547     {
 548         p_sys->i_last_time_ref = p_sys->i_time_ref;
 549         p_sys->i_time_ref +=
 550             (i_modulo_time_base * p_dec->p_sys->i_fps_num);
 551         i_time_ref = p_sys->i_time_ref;
 552     }
 553     else
 554     {
 555         i_time_ref = p_sys->i_last_time_ref +
 556             (i_modulo_time_base * p_dec->p_sys->i_fps_num);
 557     }
 558
 559 #if 0
 560     msg_Err( p_dec, "interp pts/dts (%lli,%lli), pts/dts (%lli,%lli)",
 561              p_sys->i_interpolated_pts, p_sys->i_interpolated_dts,
 562              p_vop->i_pts, p_vop->i_dts );
 563 #endif
 564
 565     if( p_dec->p_sys->i_fps_num < 5 && /* Work-around buggy streams */
 566         p_dec->fmt_in.video.i_frame_rate > 0 &&
 567         p_dec->fmt_in.video.i_frame_rate_base > 0 )
 568     {
 569         p_sys->i_interpolated_pts += I64C(1000000) *
 570         p_dec->fmt_in.video.i_frame_rate_base *
 571         p_vop->i_rate / INPUT_RATE_DEFAULT /
 572         p_dec->fmt_in.video.i_frame_rate;
 573     }
 574     else if( p_dec->p_sys->i_fps_num )
 575         p_sys->i_interpolated_pts +=
 576             ( I64C(1000000) * (i_time_ref + i_time_increment -
 577               p_sys->i_last_time - p_sys->i_last_timeincr) *
 578               p_vop->i_rate / INPUT_RATE_DEFAULT /
 579               p_dec->p_sys->i_fps_num );
 580
 581     p_sys->i_last_time = i_time_ref;
 582     p_sys->i_last_timeincr = i_time_increment;
 583
 584     /* Correct interpolated dts when we receive a new pts/dts */
 585     if( p_vop->i_pts > 0 )
 586         p_sys->i_interpolated_pts = p_vop->i_pts;
 587     if( p_vop->i_dts > 0 )
 588         p_sys->i_interpolated_dts = p_vop->i_dts;
 589
 590     if( (p_sys->i_flags & BLOCK_FLAG_TYPE_B) || !p_sys->b_frame )
 591     {
 592         /* Trivial case (DTS == PTS) */
 593
 594         p_sys->i_interpolated_dts = p_sys->i_interpolated_pts;
 595
 596         if( p_vop->i_pts > 0 )
 597             p_sys->i_interpolated_dts = p_vop->i_pts;
 598         if( p_vop->i_dts > 0 )
 599             p_sys->i_interpolated_dts = p_vop->i_dts;
 600
 601         p_sys->i_interpolated_pts = p_sys->i_interpolated_dts;
 602     }
 603     else
 604     {
 605         if( p_sys->i_last_ref_pts > 0 )
 606             p_sys->i_interpolated_dts = p_sys->i_last_ref_pts;
 607
 608         p_sys->i_last_ref_pts = p_sys->i_interpolated_pts;
 609     }
 610
 611     return VLC_SUCCESS;
 612 }
 613
 614 /* look at ffmpeg av_log2 ;) */
 615 static int vlc_log2( unsigned int v )
 616 {
 617     int n = 0;
 618     static const int vlc_log2_table[16] =
 619     {
 620         0,0,1,1,2,2,2,2, 3,3,3,3,3,3,3,3
 621     };
 622
 623     if( v&0xffff0000 )
 624     {
 625         v >>= 16;
 626         n += 16;
 627     }
 628     if( v&0xff00 )
 629     {
 630         v >>= 8;
 631         n += 8;
 632     }
 633     if( v&0xf0 )
 634     {
 635         v >>= 4;
 636         n += 4;
 637     }
 638     n += vlc_log2_table[v];
 639
 640     return n;
 641 }