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
  30 #ifdef HAVE_CONFIG_H
  31 # include "config.h"
  32 #endif
  33
  34 #include <vlc_common.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         return VLC_ENOMEM;
 164     memset( p_sys, 0, sizeof(decoder_sys_t) );
 165
 166     /* Misc init */
 167     p_sys->i_state = STATE_NOSYNC;
 168     p_sys->bytestream = block_BytestreamInit();
 169     p_sys->p_startcode[0] = 0;
 170     p_sys->p_startcode[1] = 0;
 171     p_sys->p_startcode[2] = 1;
 172     p_sys->i_offset = 0;
 173     p_sys->p_frame = NULL;
 174     p_sys->pp_last = &p_sys->p_frame;
 175
 176     /* Setup properties */
 177     es_format_Copy( &p_dec->fmt_out, &p_dec->fmt_in );
 178     p_dec->fmt_out.i_codec = VLC_FOURCC( 'm', 'p', '4', 'v' );
 179
 180     if( p_dec->fmt_in.i_extra )
 181     {
 182         /* We have a vol */
 183         p_dec->fmt_out.i_extra = p_dec->fmt_in.i_extra;
 184         p_dec->fmt_out.p_extra = malloc( p_dec->fmt_in.i_extra );
 185         memcpy( p_dec->fmt_out.p_extra, p_dec->fmt_in.p_extra,
 186                 p_dec->fmt_in.i_extra );
 187
 188         msg_Dbg( p_dec, "opening with vol size: %d", p_dec->fmt_in.i_extra );
 189         ParseVOL( p_dec, &p_dec->fmt_out,
 190                   p_dec->fmt_out.p_extra, p_dec->fmt_out.i_extra );
 191     }
 192     else
 193     {
 194         /* No vol, we'll have to look for one later on */
 195         p_dec->fmt_out.i_extra = 0;
 196         p_dec->fmt_out.p_extra = 0;
 197     }
 198
 199     /* Set callback */
 200     p_dec->pf_packetize = Packetize;
 201
 202     return VLC_SUCCESS;
 203 }
 204
 205 /*****************************************************************************
 206  * Close: clean up the packetizer
 207  *****************************************************************************/
 208 static void Close( vlc_object_t *p_this )
 209 {
 210     decoder_t *p_dec = (decoder_t*)p_this;
 211
 212     block_BytestreamRelease( &p_dec->p_sys->bytestream );
 213     if( p_dec->p_sys->p_frame ) block_ChainRelease( p_dec->p_sys->p_frame );
 214     free( p_dec->p_sys );
 215 }
 216
 217 /****************************************************************************
 218  * Packetize: the whole thing
 219  ****************************************************************************/
 220 static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
 221 {
 222     decoder_sys_t *p_sys = p_dec->p_sys;
 223     block_t       *p_pic;
 224     mtime_t       i_pts, i_dts;
 225
 226     if( pp_block == NULL || *pp_block == NULL ) return NULL;
 227
 228     if( (*pp_block)->i_flags&(BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
 229     {
 230         if( (*pp_block)->i_flags&BLOCK_FLAG_CORRUPTED )
 231         {
 232             p_sys->i_state = STATE_NOSYNC;
 233             block_BytestreamFlush( &p_sys->bytestream );
 234
 235             if( p_sys->p_frame )
 236                 block_ChainRelease( p_sys->p_frame );
 237             p_sys->p_frame = NULL;
 238             p_sys->pp_last = &p_sys->p_frame;
 239         }
 240 //        p_sys->i_interpolated_pts =
 241 //        p_sys->i_interpolated_dts =
 242 //        p_sys->i_last_ref_pts =
 243 //        p_sys->i_last_time_ref =
 244 //        p_sys->i_time_ref =
 245 //        p_sys->i_last_time =
 246 //        p_sys->i_last_timeincr = 0;
 247
 248         block_Release( *pp_block );
 249         return NULL;
 250     }
 251
 252     block_BytestreamPush( &p_sys->bytestream, *pp_block );
 253
 254     while( 1 )
 255     {
 256         switch( p_sys->i_state )
 257         {
 258
 259         case STATE_NOSYNC:
 260             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 261                     &p_sys->i_offset, p_sys->p_startcode, 3 ) == VLC_SUCCESS )
 262             {
 263                 p_sys->i_state = STATE_NEXT_SYNC;
 264             }
 265
 266             if( p_sys->i_offset )
 267             {
 268                 block_SkipBytes( &p_sys->bytestream, p_sys->i_offset );
 269                 p_sys->i_offset = 0;
 270                 block_BytestreamFlush( &p_sys->bytestream );
 271             }
 272
 273             if( p_sys->i_state != STATE_NEXT_SYNC )
 274             {
 275                 /* Need more data */
 276                 return NULL;
 277             }
 278
 279             p_sys->i_offset = 1; /* To find next startcode */
 280
 281         case STATE_NEXT_SYNC:
 282             /* TODO: If p_block == NULL, flush the buffer without checking the
 283              * next sync word */
 284
 285             /* Find the next startcode */
 286             if( block_FindStartcodeFromOffset( &p_sys->bytestream,
 287                     &p_sys->i_offset, p_sys->p_startcode, 3 ) != VLC_SUCCESS )
 288             {
 289                 /* Need more data */
 290                 return NULL;
 291             }
 292
 293             /* Get the new fragment and set the pts/dts */
 294             p_pic = block_New( p_dec, p_sys->i_offset );
 295             block_BytestreamFlush( &p_sys->bytestream );
 296             p_pic->i_pts = i_pts = p_sys->bytestream.p_block->i_pts;
 297             p_pic->i_dts = i_dts = p_sys->bytestream.p_block->i_dts;
 298             p_pic->i_rate = p_sys->bytestream.p_block->i_rate;
 299
 300             block_GetBytes( &p_sys->bytestream, p_pic->p_buffer,
 301                             p_pic->i_buffer );
 302
 303             p_sys->i_offset = 0;
 304
 305             /* Get picture if any */
 306             if( !( p_pic = ParseMPEGBlock( p_dec, p_pic ) ) )
 307             {
 308                 p_sys->i_state = STATE_NOSYNC;
 309                 break;
 310             }
 311
 312             /* don't reuse the same timestamps several times */
 313             if( i_pts == p_sys->bytestream.p_block->i_pts &&
 314                 i_dts == p_sys->bytestream.p_block->i_dts )
 315             {
 316                 p_sys->bytestream.p_block->i_pts = 0;
 317                 p_sys->bytestream.p_block->i_dts = 0;
 318             }
 319
 320             /* We've just started the stream, wait for the first PTS.
 321              * We discard here so we can still get the sequence header. */
 322             if( p_sys->i_interpolated_pts <= 0 &&
 323                 p_sys->i_interpolated_dts <= 0 )
 324             {
 325                 msg_Dbg( p_dec, "need a starting pts/dts" );
 326                 p_sys->i_state = STATE_NOSYNC;
 327                 block_Release( p_pic );
 328                 break;
 329             }
 330
 331             /* When starting the stream we can have the first frame with
 332              * a null DTS (i_interpolated_pts is initialized to 0) */
 333             if( !p_pic->i_dts ) p_pic->i_dts = p_pic->i_pts;
 334
 335             /* So p_block doesn't get re-added several times */
 336             *pp_block = block_BytestreamPop( &p_sys->bytestream );
 337
 338             p_sys->i_state = STATE_NOSYNC;
 339
 340             return p_pic;
 341         }
 342     }
 343 }
 344
 345 /*****************************************************************************
 346  * ParseMPEGBlock: Re-assemble fragments into a block containing a picture
 347  *****************************************************************************/
 348 static block_t *ParseMPEGBlock( decoder_t *p_dec, block_t *p_frag )
 349 {
 350     decoder_sys_t *p_sys = p_dec->p_sys;
 351     block_t *p_pic = NULL;
 352
 353     if( p_frag->p_buffer[3] == 0xB0 || p_frag->p_buffer[3] == 0xB1 || p_frag->p_buffer[3] == 0xB2 )
 354     {   /* VOS and USERDATA */
 355 #if 0
 356         /* Remove VOS start/end code from the original stream */
 357         block_Release( p_frag );
 358 #else
 359         /* Append the block for now since ts/ps muxers rely on VOL
 360          * being present in the stream */
 361         block_ChainLastAppend( &p_sys->pp_last, p_frag );
 362 #endif
 363         return NULL;
 364     }
 365     if( p_frag->p_buffer[3] >= 0x20 && p_frag->p_buffer[3] <= 0x2f )
 366     {
 367         /* Copy the complete VOL */
 368         if( (size_t)p_dec->fmt_out.i_extra != p_frag->i_buffer )
 369         {
 370             p_dec->fmt_out.p_extra =
 371                 realloc( p_dec->fmt_out.p_extra, p_frag->i_buffer );
 372             p_dec->fmt_out.i_extra = p_frag->i_buffer;
 373         }
 374         memcpy( p_dec->fmt_out.p_extra, p_frag->p_buffer, p_frag->i_buffer );
 375         ParseVOL( p_dec, &p_dec->fmt_out,
 376                   p_dec->fmt_out.p_extra, p_dec->fmt_out.i_extra );
 377
 378 #if 0
 379         /* Remove from the original stream */
 380         block_Release( p_frag );
 381 #else
 382         /* Append the block for now since ts/ps muxers rely on VOL
 383          * being present in the stream */
 384         block_ChainLastAppend( &p_sys->pp_last, p_frag );
 385 #endif
 386         return NULL;
 387     }
 388     else
 389     {
 390         if( !p_dec->fmt_out.i_extra )
 391         {
 392             msg_Warn( p_dec, "waiting for VOL" );
 393             block_Release( p_frag );
 394             return NULL;
 395         }
 396
 397         /* Append the block */
 398         block_ChainLastAppend( &p_sys->pp_last, p_frag );
 399     }
 400
 401     if( p_frag->p_buffer[3] == 0xb6 &&
 402         ParseVOP( p_dec, p_frag ) == VLC_SUCCESS )
 403     {
 404         /* We are dealing with a VOP */
 405         p_pic = block_ChainGather( p_sys->p_frame );
 406         p_pic->i_pts = p_sys->i_interpolated_pts;
 407         p_pic->i_dts = p_sys->i_interpolated_dts;
 408
 409         /* Reset context */
 410         p_sys->p_frame = NULL;
 411         p_sys->pp_last = &p_sys->p_frame;
 412     }
 413
 414     return p_pic;
 415 }
 416
 417 /* ParseVOL:
 418  *  TODO:
 419  *      - support aspect ratio
 420  */
 421 static int ParseVOL( decoder_t *p_dec, es_format_t *fmt,
 422                      uint8_t *p_vol, int i_vol )
 423 {
 424     decoder_sys_t *p_sys = p_dec->p_sys;
 425     int i_vo_type, i_vo_ver_id, i_ar, i_shape;
 426     bs_t s;
 427
 428     for( ;; )
 429     {
 430         if( p_vol[0] == 0x00 && p_vol[1] == 0x00 && p_vol[2] == 0x01 &&
 431             p_vol[3] >= 0x20 && p_vol[3] <= 0x2f ) break;
 432
 433         p_vol++; i_vol--;
 434         if( i_vol <= 4 ) return VLC_EGENERIC;
 435     }
 436
 437     bs_init( &s, &p_vol[4], i_vol - 4 );
 438
 439     bs_skip( &s, 1 );   /* random access */
 440     i_vo_type = bs_read( &s, 8 );
 441     if( bs_read1( &s ) )
 442     {
 443         i_vo_ver_id = bs_read( &s, 4 );
 444         bs_skip( &s, 3 );
 445     }
 446     else
 447     {
 448         i_vo_ver_id = 1;
 449     }
 450     i_ar = bs_read( &s, 4 );
 451     if( i_ar == 0xf )
 452     {
 453         int i_ar_width, i_ar_height;
 454
 455         i_ar_width = bs_read( &s, 8 );
 456         i_ar_height= bs_read( &s, 8 );
 457     }
 458     if( bs_read1( &s ) )
 459     {
 460         int i_chroma_format;
 461         int i_low_delay;
 462
 463         /* vol control parameter */
 464         i_chroma_format = bs_read( &s, 2 );
 465         i_low_delay = bs_read1( &s );
 466
 467         if( bs_read1( &s ) )
 468         {
 469             bs_skip( &s, 16 );
 470             bs_skip( &s, 16 );
 471             bs_skip( &s, 16 );
 472             bs_skip( &s, 3 );
 473             bs_skip( &s, 11 );
 474             bs_skip( &s, 1 );
 475             bs_skip( &s, 16 );
 476         }
 477     }
 478     /* shape 0->RECT, 1->BIN, 2->BIN_ONLY, 3->GRAY */
 479     i_shape = bs_read( &s, 2 );
 480     if( i_shape == 3 && i_vo_ver_id != 1 )
 481     {
 482         bs_skip( &s, 4 );
 483     }
 484
 485     if( !bs_read1( &s ) ) return VLC_EGENERIC; /* Marker */
 486
 487     p_sys->i_fps_num = bs_read( &s, 16 ); /* Time increment resolution*/
 488     if( !p_sys->i_fps_num ) p_sys->i_fps_num = 1;
 489
 490     if( !bs_read1( &s ) ) return VLC_EGENERIC; /* Marker */
 491
 492     if( bs_read1( &s ) )
 493     {
 494         int i_time_increment_bits = vlc_log2( p_sys->i_fps_num - 1 ) + 1;
 495
 496         if( i_time_increment_bits < 1 ) i_time_increment_bits = 1;
 497
 498         p_sys->i_fps_den = bs_read( &s, i_time_increment_bits );
 499     }
 500     if( i_shape == 0 )
 501     {
 502         bs_skip( &s, 1 );
 503         fmt->video.i_width = bs_read( &s, 13 );
 504         bs_skip( &s, 1 );
 505         fmt->video.i_height= bs_read( &s, 13 );
 506         bs_skip( &s, 1 );
 507     }
 508
 509     return VLC_SUCCESS;
 510 }
 511
 512 static int ParseVOP( decoder_t *p_dec, block_t *p_vop )
 513 {
 514     decoder_sys_t *p_sys = p_dec->p_sys;
 515     int64_t i_time_increment, i_time_ref;
 516     int i_modulo_time_base = 0, i_time_increment_bits;
 517     bs_t s;
 518
 519     bs_init( &s, &p_vop->p_buffer[4], p_vop->i_buffer - 4 );
 520
 521     switch( bs_read( &s, 2 ) )
 522     {
 523     case 0:
 524         p_sys->i_flags = BLOCK_FLAG_TYPE_I;
 525         break;
 526     case 1:
 527         p_sys->i_flags = BLOCK_FLAG_TYPE_P;
 528         break;
 529     case 2:
 530         p_sys->i_flags = BLOCK_FLAG_TYPE_B;
 531         p_sys->b_frame = true;
 532         break;
 533     case 3: /* gni ? */
 534         p_sys->i_flags = BLOCK_FLAG_TYPE_PB;
 535         break;
 536     }
 537
 538     while( bs_read( &s, 1 ) ) i_modulo_time_base++;
 539     if( !bs_read1( &s ) ) return VLC_EGENERIC; /* Marker */
 540
 541     /* VOP time increment */
 542     i_time_increment_bits = vlc_log2(p_dec->p_sys->i_fps_num - 1) + 1;
 543     if( i_time_increment_bits < 1 ) i_time_increment_bits = 1;
 544     i_time_increment = bs_read( &s, i_time_increment_bits );
 545
 546     /* Interpolate PTS/DTS */
 547     if( !(p_sys->i_flags & BLOCK_FLAG_TYPE_B) )
 548     {
 549         p_sys->i_last_time_ref = p_sys->i_time_ref;
 550         p_sys->i_time_ref +=
 551             (i_modulo_time_base * p_dec->p_sys->i_fps_num);
 552         i_time_ref = p_sys->i_time_ref;
 553     }
 554     else
 555     {
 556         i_time_ref = p_sys->i_last_time_ref +
 557             (i_modulo_time_base * p_dec->p_sys->i_fps_num);
 558     }
 559
 560 #if 0
 561     msg_Err( p_dec, "interp pts/dts (%lli,%lli), pts/dts (%lli,%lli)",
 562              p_sys->i_interpolated_pts, p_sys->i_interpolated_dts,
 563              p_vop->i_pts, p_vop->i_dts );
 564 #endif
 565
 566     if( p_dec->p_sys->i_fps_num < 5 && /* Work-around buggy streams */
 567         p_dec->fmt_in.video.i_frame_rate > 0 &&
 568         p_dec->fmt_in.video.i_frame_rate_base > 0 )
 569     {
 570         p_sys->i_interpolated_pts += INT64_C(1000000) *
 571         p_dec->fmt_in.video.i_frame_rate_base *
 572         p_vop->i_rate / INPUT_RATE_DEFAULT /
 573         p_dec->fmt_in.video.i_frame_rate;
 574     }
 575     else if( p_dec->p_sys->i_fps_num )
 576         p_sys->i_interpolated_pts +=
 577             ( INT64_C(1000000) * (i_time_ref + i_time_increment -
 578               p_sys->i_last_time - p_sys->i_last_timeincr) *
 579               p_vop->i_rate / INPUT_RATE_DEFAULT /
 580               p_dec->p_sys->i_fps_num );
 581
 582     p_sys->i_last_time = i_time_ref;
 583     p_sys->i_last_timeincr = i_time_increment;
 584
 585     /* Correct interpolated dts when we receive a new pts/dts */
 586     if( p_vop->i_pts > 0 )
 587         p_sys->i_interpolated_pts = p_vop->i_pts;
 588     if( p_vop->i_dts > 0 )
 589         p_sys->i_interpolated_dts = p_vop->i_dts;
 590
 591     if( (p_sys->i_flags & BLOCK_FLAG_TYPE_B) || !p_sys->b_frame )
 592     {
 593         /* Trivial case (DTS == PTS) */
 594
 595         p_sys->i_interpolated_dts = p_sys->i_interpolated_pts;
 596
 597         if( p_vop->i_pts > 0 )
 598             p_sys->i_interpolated_dts = p_vop->i_pts;
 599         if( p_vop->i_dts > 0 )
 600             p_sys->i_interpolated_dts = p_vop->i_dts;
 601
 602         p_sys->i_interpolated_pts = p_sys->i_interpolated_dts;
 603     }
 604     else
 605     {
 606         if( p_sys->i_last_ref_pts > 0 )
 607             p_sys->i_interpolated_dts = p_sys->i_last_ref_pts;
 608
 609         p_sys->i_last_ref_pts = p_sys->i_interpolated_pts;
 610     }
 611
 612     return VLC_SUCCESS;
 613 }
 614
 615 /* look at ffmpeg av_log2 ;) */
 616 static int vlc_log2( unsigned int v )
 617 {
 618     int n = 0;
 619     static const int vlc_log2_table[16] =
 620     {
 621         0,0,1,1,2,2,2,2, 3,3,3,3,3,3,3,3
 622     };
 623
 624     if( v&0xffff0000 )
 625     {
 626         v >>= 16;
 627         n += 16;
 628     }
 629     if( v&0xff00 )
 630     {
 631         v >>= 8;
 632         n += 8;
 633     }
 634     if( v&0xf0 )
 635     {
 636         v >>= 4;
 637         n += 4;
 638     }
 639     n += vlc_log2_table[v];
 640
 641     return n;
 642 }