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
  30 #ifdef HAVE_CONFIG_H
  31 # include "config.h"
  32 #endif
  33
  34 #include <vlc/vlc.h>
  35 #include <vlc_plugin.h>
  36 #include <vlc_sout.h>
  37 #include <vlc_codec.h>
  38 #include <vlc_block.h>
  39 #include <vlc_input.h>                  /* hmmm, just for INPUT_RATE_DEFAULT */
  40
  41 #include "vlc_bits.h"
  42 #include "vlc_block_helper.h"
  43
  44 /*****************************************************************************
  45  * Module descriptor
  46  *****************************************************************************/
  47 static int  Open ( vlc_object_t * );
  48 static void Close( vlc_object_t * );
  49
  50 vlc_module_begin();
  51     set_category( CAT_SOUT );
  52     set_subcategory( SUBCAT_SOUT_PACKETIZER );
  53     set_description( N_("MPEG4 video packetizer") );
  54     set_capability( "packetizer", 50 );
  55     set_callbacks( Open, Close );
  56 vlc_module_end();
  57
  58 /****************************************************************************
  59  * Local prototypes
  60  ****************************************************************************/
  61 static block_t *Packetize( decoder_t *, block_t ** );
  62
  63 struct decoder_sys_t
  64 {
  65     /*
  66      * Input properties
  67      */
  68     block_bytestream_t bytestream;
  69     int i_state;
  70     size_t i_offset;
  71     uint8_t p_startcode[3];
  72
  73     /*
  74      * Common properties
  75      */
  76     mtime_t i_interpolated_pts;
  77     mtime_t i_interpolated_dts;
  78     mtime_t i_last_ref_pts;
  79     mtime_t i_last_time_ref;
  80     mtime_t i_time_ref;
  81     mtime_t i_last_time;
  82     mtime_t i_last_timeincr;
  83
  84     unsigned int i_flags;
  85
  86     int         i_fps_num;
  87     int         i_fps_den;
  88     int         i_last_incr;
  89     int         i_last_incr_diff;
  90
  91     bool  b_frame;
  92
  93     /* Current frame being built */
  94     block_t    *p_frame;
  95     block_t    **pp_last;
  96 };
  97
  98 enum {
  99     STATE_NOSYNC,
 100     STATE_NEXT_SYNC
 101 };
 102
 103 static block_t *ParseMPEGBlock( decoder_t *, block_t * );
 104 static int ParseVOL( decoder_t *, es_format_t *, uint8_t *, int );
 105 static int ParseVOP( decoder_t *, block_t * );
 106 static int vlc_log2( unsigned int );
 107
 108 #define VIDEO_OBJECT_MASK                       0x01f
 109 #define VIDEO_OBJECT_LAYER_MASK                 0x00f
 110
 111 #define VIDEO_OBJECT_START_CODE                 0x100
 112 #define VIDEO_OBJECT_LAYER_START_CODE           0x120
 113 #define VISUAL_OBJECT_SEQUENCE_START_CODE       0x1b0
 114 #define VISUAL_OBJECT_SEQUENCE_END_CODE         0x1b1
 115 #define USER_DATA_START_CODE                    0x1b2
 116 #define GROUP_OF_VOP_START_CODE                 0x1b3
 117 #define VIDEO_SESSION_ERROR_CODE                0x1b4
 118 #define VISUAL_OBJECT_START_CODE                0x1b5
 119 #define VOP_START_CODE                          0x1b6
 120 #define FACE_OBJECT_START_CODE                  0x1ba
 121 #define FACE_OBJECT_PLANE_START_CODE            0x1bb
 122 #define MESH_OBJECT_START_CODE                  0x1bc
 123 #define MESH_OBJECT_PLANE_START_CODE            0x1bd
 124 #define STILL_TEXTURE_OBJECT_START_CODE         0x1be
 125 #define TEXTURE_SPATIAL_LAYER_START_CODE        0x1bf
 126 #define TEXTURE_SNR_LAYER_START_CODE            0x1c0
 127
 128 /*****************************************************************************
 129  * Open: probe the packetizer and return score
 130  *****************************************************************************/
 131 static int Open( vlc_object_t *p_this )
 132 {
 133     decoder_t     *p_dec = (decoder_t*)p_this;
 134     decoder_sys_t *p_sys;
 135
 136     switch( p_dec->fmt_in.i_codec )
 137     {
 138         case VLC_FOURCC( 'm', '4', 's', '2'):
 139         case VLC_FOURCC( 'M', '4', 'S', '2'):
 140         case VLC_FOURCC( 'm', 'p', '4', 's'):
 141         case VLC_FOURCC( 'M', 'P', '4', 'S'):
 142         case VLC_FOURCC( 'm', 'p', '4', 'v'):
 143         case VLC_FOURCC( 'M', 'P', '4', 'V'):
 144         case VLC_FOURCC( 'D', 'I', 'V', 'X'):
 145         case VLC_FOURCC( 'd', 'i', 'v', 'x'):
 146         case VLC_FOURCC( 'X', 'V', 'I', 'D'):
 147         case VLC_FOURCC( 'X', 'v', 'i', 'D'):
 148         case VLC_FOURCC( 'x', 'v', 'i', 'd'):
 149         case VLC_FOURCC( 'D', 'X', '5', '0'):
 150         case VLC_FOURCC( 'd', 'x', '5', '0'):
 151         case VLC_FOURCC( 0x04, 0,   0,   0):
 152         case VLC_FOURCC( '3', 'I', 'V', '2'):
 153         case VLC_FOURCC( 'm', '4', 'c', 'c'):
 154         case VLC_FOURCC( 'M', '4', 'C', 'C'):
 155             break;
 156
 157         default:
 158             return VLC_EGENERIC;
 159     }
 160
 161     /* Allocate the memory needed to store the decoder's structure */
 162     if( ( p_dec->p_sys = p_sys = malloc( sizeof(decoder_sys_t) ) ) == NULL )
 163     {
 164         msg_Err( p_dec, "out of memory" );
 165         return VLC_EGENERIC;
 166     }
 167     memset( p_sys, 0, sizeof(decoder_sys_t) );
 168
 169     /* Misc init */
 170     p_sys->i_state = STATE_NOSYNC;
 171     p_sys->bytestream = block_BytestreamInit();
 172     p_sys->p_startcode[0] = 0;
 173     p_sys->p_startcode[1] = 0;
 174     p_sys->p_startcode[2] = 1;
 175     p_sys->i_offset = 0;
 176     p_sys->p_frame = NULL;
 177     p_sys->pp_last = &p_sys->p_frame;
 178
 179     /* Setup properties */
 180     es_format_Copy( &p_dec->fmt_out, &p_dec->fmt_in );
 181     p_dec->fmt_out.i_codec = VLC_FOURCC( 'm', 'p', '4', 'v' );
 182
 183     if( p_dec->fmt_in.i_extra )
 184     {
 185         /* We have a vol */
 186         p_dec->fmt_out.i_extra = p_dec->fmt_in.i_extra;
 187         p_dec->fmt_out.p_extra = malloc( p_dec->fmt_in.i_extra );
 188         memcpy( p_dec->fmt_out.p_extra, p_dec->fmt_in.p_extra,
 189                 p_dec->fmt_in.i_extra );
 190
 191         msg_Dbg( p_dec, "opening with vol size: %d", p_dec->fmt_in.i_extra );
 192         ParseVOL( p_dec, &p_dec->fmt_out,
 193                   p_dec->fmt_out.p_extra, p_dec->fmt_out.i_extra );
 194     }
 195     else
 196     {
 197         /* No vol, we'll have to look for one later on */
 198         p_dec->fmt_out.i_extra = 0;
 199         p_dec->fmt_out.p_extra = 0;
 200     }
 201
 202     /* Set callback */
 203     p_dec->pf_packetize = Packetize;
 204
 205     return VLC_SUCCESS;
 206 }
 207
 208 /*****************************************************************************
 209  * Close: clean up the packetizer
 210  *****************************************************************************/
 211 static void Close( vlc_object_t *p_this )
 212 {
 213     decoder_t *p_dec = (decoder_t*)p_this;
 214
 215     block_BytestreamRelease( &p_dec->p_sys->bytestream );
 216     if( p_dec->p_sys->p_frame ) block_ChainRelease( p_dec->p_sys->p_frame );
 217     free( p_dec->p_sys );
 218 }
 219
 220 /****************************************************************************
 221  * Packetize: the whole thing
 222  ****************************************************************************/
 223 static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
 224 {
 225     decoder_sys_t *p_sys = p_dec->p_sys;
 226     block_t       *p_pic;
 227     mtime_t       i_pts, i_dts;
 228
 229     if( pp_block == NULL || *pp_block == NULL ) return NULL;
 230
 231     if( (*pp_block)->i_flags&(BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 232     {
 233         if( (*pp_block)->i_flags&BLOCK_FLAG_CORRUPTED )
 234         {
 235             p_sys->i_state = STATE_NOSYNC;
 236             block_BytestreamFlush( &p_sys->bytestream );
 237
 238             if( p_sys->p_frame )
 239                 block_ChainRelease( p_sys->p_frame );
 240             p_sys->p_frame = NULL;
 241             p_sys->pp_last = &p_sys->p_frame;
 242         }
 243 //        p_sys->i_interpolated_pts =
 244 //        p_sys->i_interpolated_dts =
 245 //        p_sys->i_last_ref_pts =
 246 //        p_sys->i_last_time_ref =
 247 //        p_sys->i_time_ref =
 248 //        p_sys->i_last_time =
 249 //        p_sys->i_last_timeincr = 0;
 250
 251         block_Release( *pp_block );
 252         return NULL;
 253     }
 254
 255     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 256
 257     while( 1 )
 258     {
 259         switch( p_sys->i_state )
 260         {
 261
 262         case STATE_NOSYNC:
 263             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 264                     &p_sys->i_offset, p_sys->p_startcode, 3 ) == VLC_SUCCESS )
 265             {
 266                 p_sys->i_state = STATE_NEXT_SYNC;
 267             }
 268
 269             if( p_sys->i_offset )
 270             {
 271                 block_SkipBytes( &p_sys->bytestream, p_sys->i_offset );
 272                 p_sys->i_offset = 0;
 273                 block_BytestreamFlush( &p_sys->bytestream );
 274             }
 275
 276             if( p_sys->i_state != STATE_NEXT_SYNC )
 277             {
 278                 /* Need more data */
 279                 return NULL;
 280             }
 281
 282             p_sys->i_offset = 1; /* To find next startcode */
 283
 284         case STATE_NEXT_SYNC:
 285             /* TODO: If p_block == NULL, flush the buffer without checking the
 286              * next sync word */
 287
 288             /* Find the next startcode */
 289             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 290                     &p_sys->i_offset, p_sys->p_startcode, 3 ) != VLC_SUCCESS )
 291             {
 292                 /* Need more data */
 293                 return NULL;
 294             }
 295
 296             /* Get the new fragment and set the pts/dts */
 297             p_pic = block_New( p_dec, p_sys->i_offset );
 298             block_BytestreamFlush( &p_sys->bytestream );
 299             p_pic->i_pts = i_pts = p_sys->bytestream.p_block->i_pts;
 300             p_pic->i_dts = i_dts = p_sys->bytestream.p_block->i_dts;
 301             p_pic->i_rate = p_sys->bytestream.p_block->i_rate;
 302
 303             block_GetBytes( &p_sys->bytestream, p_pic->p_buffer,
 304                             p_pic->i_buffer );
 305
 306             p_sys->i_offset = 0;
 307
 308             /* Get picture if any */
 309             if( !( p_pic = ParseMPEGBlock( p_dec, p_pic ) ) )
 310             {
 311                 p_sys->i_state = STATE_NOSYNC;
 312                 break;
 313             }
 314
 315             /* don't reuse the same timestamps several times */
 316             if( i_pts == p_sys->bytestream.p_block->i_pts &&
 317                 i_dts == p_sys->bytestream.p_block->i_dts )
 318             {
 319                 p_sys->bytestream.p_block->i_pts = 0;
 320                 p_sys->bytestream.p_block->i_dts = 0;
 321             }
 322
 323             /* We've just started the stream, wait for the first PTS.
 324              * We discard here so we can still get the sequence header. */
 325             if( p_sys->i_interpolated_pts <= 0 &&
 326                 p_sys->i_interpolated_dts <= 0 )
 327             {
 328                 msg_Dbg( p_dec, "need a starting pts/dts" );
 329                 p_sys->i_state = STATE_NOSYNC;
 330                 block_Release( p_pic );
 331                 break;
 332             }
 333
 334             /* When starting the stream we can have the first frame with
 335              * a null DTS (i_interpolated_pts is initialized to 0) */
 336             if( !p_pic->i_dts ) p_pic->i_dts = p_pic->i_pts;
 337
 338             /* So p_block doesn't get re-added several times */
 339             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 340
 341             p_sys->i_state = STATE_NOSYNC;
 342
 343             return p_pic;
 344         }
 345     }
 346 }
 347
 348 /*****************************************************************************
 349  * ParseMPEGBlock: Re-assemble fragments into a block containing a picture
 350  *****************************************************************************/
 351 static block_t *ParseMPEGBlock( decoder_t *p_dec, block_t *p_frag )
 352 {
 353     decoder_sys_t *p_sys = p_dec->p_sys;
 354     block_t *p_pic = NULL;
 355
 356     if( p_frag->p_buffer[3] == 0xB0 || p_frag->p_buffer[3] == 0xB1 || p_frag->p_buffer[3] == 0xB2 )
 357     {   /* VOS and USERDATA */
 358 #if 0
 359         /* Remove VOS start/end code from the original stream */
 360         block_Release( p_frag );
 361 #else
 362         /* Append the block for now since ts/ps muxers rely on VOL
 363          * being present in the stream */
 364         block_ChainLastAppend( &p_sys->pp_last, p_frag );
 365 #endif
 366         return NULL;
 367     }
 368     if( p_frag->p_buffer[3] >= 0x20 && p_frag->p_buffer[3] <= 0x2f )
 369     {
 370         /* Copy the complete VOL */
 371         if( (size_t)p_dec->fmt_out.i_extra != p_frag->i_buffer )
 372         {
 373             p_dec->fmt_out.p_extra =
 374                 realloc( p_dec->fmt_out.p_extra, p_frag->i_buffer );
 375             p_dec->fmt_out.i_extra = p_frag->i_buffer;
 376         }
 377         memcpy( p_dec->fmt_out.p_extra, p_frag->p_buffer, p_frag->i_buffer );
 378         ParseVOL( p_dec, &p_dec->fmt_out,
 379                   p_dec->fmt_out.p_extra, p_dec->fmt_out.i_extra );
 380
 381 #if 0
 382         /* Remove from the original stream */
 383         block_Release( p_frag );
 384 #else
 385         /* Append the block for now since ts/ps muxers rely on VOL
 386          * being present in the stream */
 387         block_ChainLastAppend( &p_sys->pp_last, p_frag );
 388 #endif
 389         return NULL;
 390     }
 391     else
 392     {
 393         if( !p_dec->fmt_out.i_extra )
 394         {
 395             msg_Warn( p_dec, "waiting for VOL" );
 396             block_Release( p_frag );
 397             return NULL;
 398         }
 399
 400         /* Append the block */
 401         block_ChainLastAppend( &p_sys->pp_last, p_frag );
 402     }
 403
 404     if( p_frag->p_buffer[3] == 0xb6 &&
 405         ParseVOP( p_dec, p_frag ) == VLC_SUCCESS )
 406     {
 407         /* We are dealing with a VOP */
 408         p_pic = block_ChainGather( p_sys->p_frame );
 409         p_pic->i_pts = p_sys->i_interpolated_pts;
 410         p_pic->i_dts = p_sys->i_interpolated_dts;
 411
 412         /* Reset context */
 413         p_sys->p_frame = NULL;
 414         p_sys->pp_last = &p_sys->p_frame;
 415     }
 416
 417     return p_pic;
 418 }
 419
 420 /* ParseVOL:
 421  *  TODO:
 422  *      - support aspect ratio
 423  */
 424 static int ParseVOL( decoder_t *p_dec, es_format_t *fmt,
 425                      uint8_t *p_vol, int i_vol )
 426 {
 427     decoder_sys_t *p_sys = p_dec->p_sys;
 428     int i_vo_type, i_vo_ver_id, i_ar, i_shape;
 429     bs_t s;
 430
 431     for( ;; )
 432     {
 433         if( p_vol[0] == 0x00 && p_vol[1] == 0x00 && p_vol[2] == 0x01 &&
 434             p_vol[3] >= 0x20 && p_vol[3] <= 0x2f ) break;
 435
 436         p_vol++; i_vol--;
 437         if( i_vol <= 4 ) return VLC_EGENERIC;
 438     }
 439
 440     bs_init( &s, &p_vol[4], i_vol - 4 );
 441
 442     bs_skip( &s, 1 );   /* random access */
 443     i_vo_type = bs_read( &s, 8 );
 444     if( bs_read1( &s ) )
 445     {
 446         i_vo_ver_id = bs_read( &s, 4 );
 447         bs_skip( &s, 3 );
 448     }
 449     else
 450     {
 451         i_vo_ver_id = 1;
 452     }
 453     i_ar = bs_read( &s, 4 );
 454     if( i_ar == 0xf )
 455     {
 456         int i_ar_width, i_ar_height;
 457
 458         i_ar_width = bs_read( &s, 8 );
 459         i_ar_height= bs_read( &s, 8 );
 460     }
 461     if( bs_read1( &s ) )
 462     {
 463         int i_chroma_format;
 464         int i_low_delay;
 465
 466         /* vol control parameter */
 467         i_chroma_format = bs_read( &s, 2 );
 468         i_low_delay = bs_read1( &s );
 469
 470         if( bs_read1( &s ) )
 471         {
 472             bs_skip( &s, 16 );
 473             bs_skip( &s, 16 );
 474             bs_skip( &s, 16 );
 475             bs_skip( &s, 3 );
 476             bs_skip( &s, 11 );
 477             bs_skip( &s, 1 );
 478             bs_skip( &s, 16 );
 479         }
 480     }
 481     /* shape 0->RECT, 1->BIN, 2->BIN_ONLY, 3->GRAY */
 482     i_shape = bs_read( &s, 2 );
 483     if( i_shape == 3 && i_vo_ver_id != 1 )
 484     {
 485         bs_skip( &s, 4 );
 486     }
 487
 488     if( !bs_read1( &s ) ) return VLC_EGENERIC; /* Marker */
 489
 490     p_sys->i_fps_num = bs_read( &s, 16 ); /* Time increment resolution*/
 491     if( !p_sys->i_fps_num ) p_sys->i_fps_num = 1;
 492
 493     if( !bs_read1( &s ) ) return VLC_EGENERIC; /* Marker */
 494
 495     if( bs_read1( &s ) )
 496     {
 497         int i_time_increment_bits = vlc_log2( p_sys->i_fps_num - 1 ) + 1;
 498
 499         if( i_time_increment_bits < 1 ) i_time_increment_bits = 1;
 500
 501         p_sys->i_fps_den = bs_read( &s, i_time_increment_bits );
 502     }
 503     if( i_shape == 0 )
 504     {
 505         bs_skip( &s, 1 );
 506         fmt->video.i_width = bs_read( &s, 13 );
 507         bs_skip( &s, 1 );
 508         fmt->video.i_height= bs_read( &s, 13 );
 509         bs_skip( &s, 1 );
 510     }
 511
 512     return VLC_SUCCESS;
 513 }
 514
 515 static int ParseVOP( decoder_t *p_dec, block_t *p_vop )
 516 {
 517     decoder_sys_t *p_sys = p_dec->p_sys;
 518     int64_t i_time_increment, i_time_ref;
 519     int i_modulo_time_base = 0, i_time_increment_bits;
 520     bs_t s;
 521
 522     bs_init( &s, &p_vop->p_buffer[4], p_vop->i_buffer - 4 );
 523
 524     switch( bs_read( &s, 2 ) )
 525     {
 526     case 0:
 527         p_sys->i_flags = BLOCK_FLAG_TYPE_I;
 528         break;
 529     case 1:
 530         p_sys->i_flags = BLOCK_FLAG_TYPE_P;
 531         break;
 532     case 2:
 533         p_sys->i_flags = BLOCK_FLAG_TYPE_B;
 534         p_sys->b_frame = true;
 535         break;
 536     case 3: /* gni ? */
 537         p_sys->i_flags = BLOCK_FLAG_TYPE_PB;
 538         break;
 539     }
 540
 541     while( bs_read( &s, 1 ) ) i_modulo_time_base++;
 542     if( !bs_read1( &s ) ) return VLC_EGENERIC; /* Marker */
 543
 544     /* VOP time increment */
 545     i_time_increment_bits = vlc_log2(p_dec->p_sys->i_fps_num - 1) + 1;
 546     if( i_time_increment_bits < 1 ) i_time_increment_bits = 1;
 547     i_time_increment = bs_read( &s, i_time_increment_bits );
 548
 549     /* Interpolate PTS/DTS */
 550     if( !(p_sys->i_flags & BLOCK_FLAG_TYPE_B) )
 551     {
 552         p_sys->i_last_time_ref = p_sys->i_time_ref;
 553         p_sys->i_time_ref +=
 554             (i_modulo_time_base * p_dec->p_sys->i_fps_num);
 555         i_time_ref = p_sys->i_time_ref;
 556     }
 557     else
 558     {
 559         i_time_ref = p_sys->i_last_time_ref +
 560             (i_modulo_time_base * p_dec->p_sys->i_fps_num);
 561     }
 562
 563 #if 0
 564     msg_Err( p_dec, "interp pts/dts (%lli,%lli), pts/dts (%lli,%lli)",
 565              p_sys->i_interpolated_pts, p_sys->i_interpolated_dts,
 566              p_vop->i_pts, p_vop->i_dts );
 567 #endif
 568
 569     if( p_dec->p_sys->i_fps_num < 5 && /* Work-around buggy streams */
 570         p_dec->fmt_in.video.i_frame_rate > 0 &&
 571         p_dec->fmt_in.video.i_frame_rate_base > 0 )
 572     {
 573         p_sys->i_interpolated_pts += INT64_C(1000000) *
 574         p_dec->fmt_in.video.i_frame_rate_base *
 575         p_vop->i_rate / INPUT_RATE_DEFAULT /
 576         p_dec->fmt_in.video.i_frame_rate;
 577     }
 578     else if( p_dec->p_sys->i_fps_num )
 579         p_sys->i_interpolated_pts +=
 580             ( INT64_C(1000000) * (i_time_ref + i_time_increment -
 581               p_sys->i_last_time - p_sys->i_last_timeincr) *
 582               p_vop->i_rate / INPUT_RATE_DEFAULT /
 583               p_dec->p_sys->i_fps_num );
 584
 585     p_sys->i_last_time = i_time_ref;
 586     p_sys->i_last_timeincr = i_time_increment;
 587
 588     /* Correct interpolated dts when we receive a new pts/dts */
 589     if( p_vop->i_pts > 0 )
 590         p_sys->i_interpolated_pts = p_vop->i_pts;
 591     if( p_vop->i_dts > 0 )
 592         p_sys->i_interpolated_dts = p_vop->i_dts;
 593
 594     if( (p_sys->i_flags & BLOCK_FLAG_TYPE_B) || !p_sys->b_frame )
 595     {
 596         /* Trivial case (DTS == PTS) */
 597
 598         p_sys->i_interpolated_dts = p_sys->i_interpolated_pts;
 599
 600         if( p_vop->i_pts > 0 )
 601             p_sys->i_interpolated_dts = p_vop->i_pts;
 602         if( p_vop->i_dts > 0 )
 603             p_sys->i_interpolated_dts = p_vop->i_dts;
 604
 605         p_sys->i_interpolated_pts = p_sys->i_interpolated_dts;
 606     }
 607     else
 608     {
 609         if( p_sys->i_last_ref_pts > 0 )
 610             p_sys->i_interpolated_dts = p_sys->i_last_ref_pts;
 611
 612         p_sys->i_last_ref_pts = p_sys->i_interpolated_pts;
 613     }
 614
 615     return VLC_SUCCESS;
 616 }
 617
 618 /* look at ffmpeg av_log2 ;) */
 619 static int vlc_log2( unsigned int v )
 620 {
 621     int n = 0;
 622     static const int vlc_log2_table[16] =
 623     {
 624         0,0,1,1,2,2,2,2, 3,3,3,3,3,3,3,3
 625     };
 626
 627     if( v&0xffff0000 )
 628     {
 629         v >>= 16;
 630         n += 16;
 631     }
 632     if( v&0xff00 )
 633     {
 634         v >>= 8;
 635         n += 8;
 636     }
 637     if( v&0xf0 )
 638     {
 639         v >>= 4;
 640         n += 4;
 641     }
 642     n += vlc_log2_table[v];
 643
 644     return n;
 645 }