modules/packetizer/mpeg4video.c

   1 /*****************************************************************************
   2  * mpeg4video.c: mpeg 4 video packetizer
   3  *****************************************************************************
   4  * Copyright (C) 2001-2006 VLC authors and VideoLAN
   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 it
  12  * under the terms of the GNU Lesser General Public License as published by
  13  * the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU Lesser General Public License
  22  * along with this program; if not, write to the Free Software Foundation,
  23  * 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
  40 #include <vlc_bits.h>
  41 #include <vlc_block_helper.h>
  42 #include "packetizer_helper.h"
  43 #include "startcode_helper.h"
  44 #include "hxxx_nal.h" /* colour values/mappings */
  45
  46 /*****************************************************************************
  47  * Module descriptor
  48  *****************************************************************************/
  49 static int  Open ( vlc_object_t * );
  50 static void Close( vlc_object_t * );
  51
  52 vlc_module_begin ()
  53     set_category( CAT_SOUT )
  54     set_subcategory( SUBCAT_SOUT_PACKETIZER )
  55     set_description( N_("MPEG4 video packetizer") )
  56     set_capability( "packetizer", 50 )
  57     set_callbacks( Open, Close )
  58 vlc_module_end ()
  59
  60 /****************************************************************************
  61  * Local prototypes
  62  ****************************************************************************/
  63 struct decoder_sys_t
  64 {
  65     /*
  66      * Input properties
  67      */
  68     packetizer_t packetizer;
  69
  70     /*
  71      * Common properties
  72      */
  73     mtime_t i_interpolated_pts;
  74     mtime_t i_interpolated_dts;
  75     mtime_t i_last_ref_pts;
  76     mtime_t i_last_time_ref;
  77     mtime_t i_time_ref;
  78     mtime_t i_last_time;
  79     mtime_t i_last_timeincr;
  80
  81     unsigned int i_flags;
  82
  83     int         i_fps_num;
  84     int         i_fps_den;
  85     int         i_last_incr;
  86     int         i_last_incr_diff;
  87
  88     bool  b_frame;
  89
  90     /* Current frame being built */
  91     block_t    *p_frame;
  92     block_t    **pp_last;
  93 };
  94
  95 static block_t *Packetize( decoder_t *, block_t ** );
  96 static void PacketizeFlush( decoder_t * );
  97
  98 static void PacketizeReset( void *p_private, bool b_broken );
  99 static block_t *PacketizeParse( void *p_private, bool *pb_ts_used, block_t * );
 100 static int PacketizeValidate( void *p_private, block_t * );
 101
 102 static block_t *ParseMPEGBlock( decoder_t *, block_t * );
 103 static int ParseVOL( decoder_t *, es_format_t *, uint8_t *, int );
 104 static int ParseVO( decoder_t *, block_t * );
 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 RESERVED_START_CODE                     0x130
 114 #define VISUAL_OBJECT_SEQUENCE_START_CODE       0x1b0
 115 #define VISUAL_OBJECT_SEQUENCE_END_CODE         0x1b1
 116 #define USER_DATA_START_CODE                    0x1b2
 117 #define GROUP_OF_VOP_START_CODE                 0x1b3
 118 #define VIDEO_SESSION_ERROR_CODE                0x1b4
 119 #define VISUAL_OBJECT_START_CODE                0x1b5
 120 #define VOP_START_CODE                          0x1b6
 121 #define FACE_OBJECT_START_CODE                  0x1ba
 122 #define FACE_OBJECT_PLANE_START_CODE            0x1bb
 123 #define MESH_OBJECT_START_CODE                  0x1bc
 124 #define MESH_OBJECT_PLANE_START_CODE            0x1bd
 125 #define STILL_TEXTURE_OBJECT_START_CODE         0x1be
 126 #define TEXTURE_SPATIAL_LAYER_START_CODE        0x1bf
 127 #define TEXTURE_SNR_LAYER_START_CODE            0x1c0
 128
 129 static const uint8_t p_mp4v_startcode[3] = { 0x00, 0x00, 0x01 };
 130
 131 /*****************************************************************************
 132  * Open: probe the packetizer and return score
 133  *****************************************************************************/
 134 static int Open( vlc_object_t *p_this )
 135 {
 136     decoder_t     *p_dec = (decoder_t*)p_this;
 137     decoder_sys_t *p_sys;
 138
 139     if( p_dec->fmt_in.i_codec != VLC_CODEC_MP4V )
 140         return VLC_EGENERIC;
 141
 142     /* Allocate the memory needed to store the decoder's structure */
 143     if( ( p_dec->p_sys = p_sys = malloc( sizeof(decoder_sys_t) ) ) == NULL )
 144         return VLC_ENOMEM;
 145     memset( p_sys, 0, sizeof(decoder_sys_t) );
 146
 147     /* Misc init */
 148     packetizer_Init( &p_sys->packetizer,
 149                      p_mp4v_startcode, sizeof(p_mp4v_startcode), startcode_FindAnnexB,
 150                      NULL, 0, 4,
 151                      PacketizeReset, PacketizeParse, PacketizeValidate, p_dec );
 152
 153     p_sys->p_frame = NULL;
 154     p_sys->pp_last = &p_sys->p_frame;
 155
 156     /* Setup properties */
 157     es_format_Copy( &p_dec->fmt_out, &p_dec->fmt_in );
 158     p_dec->fmt_out.i_codec = VLC_CODEC_MP4V;
 159
 160     if( p_dec->fmt_out.i_extra )
 161     {
 162         /* We have a vol */
 163         msg_Dbg( p_dec, "opening with vol size: %d", p_dec->fmt_out.i_extra );
 164         ParseVOL( p_dec, &p_dec->fmt_out,
 165                   p_dec->fmt_out.p_extra, p_dec->fmt_out.i_extra );
 166     }
 167
 168     /* Set callback */
 169     p_dec->pf_packetize = Packetize;
 170     p_dec->pf_flush = PacketizeFlush;
 171
 172     return VLC_SUCCESS;
 173 }
 174
 175 /*****************************************************************************
 176  * Close: clean up the packetizer
 177  *****************************************************************************/
 178 static void Close( vlc_object_t *p_this )
 179 {
 180     decoder_t *p_dec = (decoder_t*)p_this;
 181     decoder_sys_t *p_sys = p_dec->p_sys;
 182
 183     packetizer_Clean( &p_sys->packetizer );
 184     if( p_sys->p_frame )
 185         block_ChainRelease( p_sys->p_frame );
 186     free( p_sys );
 187 }
 188
 189 /****************************************************************************
 190  * Packetize: the whole thing
 191  ****************************************************************************/
 192 static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
 193 {
 194     decoder_sys_t *p_sys = p_dec->p_sys;
 195
 196     return packetizer_Packetize( &p_sys->packetizer, pp_block );
 197 }
 198
 199 static void PacketizeFlush( decoder_t *p_dec )
 200 {
 201     decoder_sys_t *p_sys = p_dec->p_sys;
 202
 203     packetizer_Flush( &p_sys->packetizer );
 204 }
 205
 206 /*****************************************************************************
 207  * Helpers:
 208  *****************************************************************************/
 209 static void PacketizeReset( void *p_private, bool b_broken )
 210 {
 211     decoder_t *p_dec = p_private;
 212     decoder_sys_t *p_sys = p_dec->p_sys;
 213
 214     if( b_broken )
 215     {
 216         if( p_sys->p_frame )
 217             block_ChainRelease( p_sys->p_frame );
 218         p_sys->p_frame = NULL;
 219         p_sys->pp_last = &p_sys->p_frame;
 220     }
 221
 222     p_sys->i_interpolated_pts =
 223     p_sys->i_interpolated_dts =
 224     p_sys->i_last_ref_pts = VLC_TS_INVALID;
 225
 226     p_sys->i_last_time_ref =
 227     p_sys->i_time_ref =
 228     p_sys->i_last_time =
 229     p_sys->i_last_timeincr = 0;
 230 }
 231
 232 static block_t *PacketizeParse( void *p_private, bool *pb_ts_used, block_t *p_block )
 233 {
 234     decoder_t *p_dec = p_private;
 235     const mtime_t i_dts = p_block->i_dts;
 236     const mtime_t i_pts = p_block->i_pts;
 237
 238     block_t *p_au = ParseMPEGBlock( p_dec, p_block );
 239
 240     *pb_ts_used = p_au &&  p_au->i_dts == i_dts && p_au->i_pts == i_pts;
 241
 242     return p_au;
 243 }
 244
 245
 246 static int PacketizeValidate( void *p_private, block_t *p_au )
 247 {
 248     decoder_t *p_dec = p_private;
 249     decoder_sys_t *p_sys = p_dec->p_sys;
 250
 251     /* We've just started the stream, wait for the first PTS.
 252      * We discard here so we can still get the sequence header. */
 253     if( p_sys->i_interpolated_pts <= VLC_TS_INVALID &&
 254         p_sys->i_interpolated_dts <= VLC_TS_INVALID )
 255     {
 256         msg_Dbg( p_dec, "need a starting pts/dts" );
 257         return VLC_EGENERIC;
 258     }
 259
 260     /* When starting the stream we can have the first frame with
 261      * a null DTS (i_interpolated_pts is initialized to 0) */
 262     if( !p_au->i_dts )
 263         p_au->i_dts = p_au->i_pts;
 264     return VLC_SUCCESS;
 265 }
 266
 267 /*****************************************************************************
 268  * ParseMPEGBlock: Re-assemble fragments into a block containing a picture
 269  *****************************************************************************/
 270 static block_t *ParseMPEGBlock( decoder_t *p_dec, block_t *p_frag )
 271 {
 272     decoder_sys_t *p_sys = p_dec->p_sys;
 273     block_t *p_pic = NULL;
 274
 275     if( p_frag->i_buffer < 4 )
 276         return p_frag;
 277
 278     const uint32_t i_startcode = GetDWBE( p_frag->p_buffer );
 279     if( i_startcode == VISUAL_OBJECT_SEQUENCE_START_CODE ||
 280         i_startcode == VISUAL_OBJECT_SEQUENCE_END_CODE ||
 281         i_startcode == USER_DATA_START_CODE )
 282     {   /* VOS and USERDATA */
 283 #if 0
 284         /* Remove VOS start/end code from the original stream */
 285         block_Release( p_frag );
 286 #else
 287         /* Append the block for now since ts/ps muxers rely on VOL
 288          * being present in the stream */
 289         block_ChainLastAppend( &p_sys->pp_last, p_frag );
 290 #endif
 291         return NULL;
 292     }
 293     else if( i_startcode >= VIDEO_OBJECT_LAYER_START_CODE &&
 294              i_startcode < RESERVED_START_CODE )
 295     {
 296         /* Copy the complete VOL */
 297         if( (size_t)p_dec->fmt_out.i_extra != p_frag->i_buffer )
 298         {
 299             p_dec->fmt_out.p_extra =
 300                 xrealloc( p_dec->fmt_out.p_extra, p_frag->i_buffer );
 301             p_dec->fmt_out.i_extra = p_frag->i_buffer;
 302         }
 303         memcpy( p_dec->fmt_out.p_extra, p_frag->p_buffer, p_frag->i_buffer );
 304         ParseVOL( p_dec, &p_dec->fmt_out,
 305                   p_dec->fmt_out.p_extra, p_dec->fmt_out.i_extra );
 306
 307 #if 0
 308         /* Remove from the original stream */
 309         block_Release( p_frag );
 310 #else
 311         /* Append the block for now since ts/ps muxers rely on VOL
 312          * being present in the stream */
 313         block_ChainLastAppend( &p_sys->pp_last, p_frag );
 314 #endif
 315         return NULL;
 316     }
 317     else
 318     {
 319         if( !p_dec->fmt_out.i_extra )
 320         {
 321             msg_Warn( p_dec, "waiting for VOL" );
 322             block_Release( p_frag );
 323             return NULL;
 324         }
 325
 326         /* Append the block */
 327         block_ChainLastAppend( &p_sys->pp_last, p_frag );
 328     }
 329
 330     if( i_startcode == VISUAL_OBJECT_START_CODE )
 331     {
 332         ParseVO( p_dec, p_frag );
 333     }
 334     else
 335     if( i_startcode == VOP_START_CODE &&
 336         ParseVOP( p_dec, p_frag ) == VLC_SUCCESS )
 337     {
 338         /* We are dealing with a VOP */
 339         p_pic = block_ChainGather( p_sys->p_frame );
 340         p_pic->i_flags = p_sys->i_flags;
 341         p_pic->i_pts = p_sys->i_interpolated_pts;
 342         p_pic->i_dts = p_sys->i_interpolated_dts;
 343
 344         /* Reset context */
 345         p_sys->p_frame = NULL;
 346         p_sys->pp_last = &p_sys->p_frame;
 347     }
 348
 349     return p_pic;
 350 }
 351
 352 /* ParseVOL:
 353  *  TODO:
 354  *      - support aspect ratio
 355  */
 356 static int ParseVOL( decoder_t *p_dec, es_format_t *fmt,
 357                      uint8_t *p_vol, int i_vol )
 358 {
 359     decoder_sys_t *p_sys = p_dec->p_sys;
 360     int i_vo_ver_id, i_ar, i_shape;
 361     bs_t s;
 362
 363     for( ;; )
 364     {
 365         if( p_vol[0] == 0x00 && p_vol[1] == 0x00 && p_vol[2] == 0x01 &&
 366             p_vol[3] >= 0x20 && p_vol[3] <= 0x2f ) break;
 367
 368         p_vol++; i_vol--;
 369         if( i_vol <= 4 ) return VLC_EGENERIC;
 370     }
 371
 372     bs_init( &s, &p_vol[4], i_vol - 4 );
 373
 374     bs_skip( &s, 1 );   /* random access */
 375     bs_skip( &s, 8 );   /* vo_type */
 376     if( bs_read1( &s ) )
 377     {
 378         i_vo_ver_id = bs_read( &s, 4 );
 379         bs_skip( &s, 3 );
 380     }
 381     else
 382     {
 383         i_vo_ver_id = 1;
 384     }
 385     i_ar = bs_read( &s, 4 );
 386     if( i_ar == 0xf )
 387     {
 388         bs_skip( &s, 8 );  /* ar_width */
 389         bs_skip( &s, 8 );  /* ar_height */
 390     }
 391     if( bs_read1( &s ) )
 392     {
 393         /* vol control parameter */
 394         bs_skip( &s, 2 ); /* chroma_format */
 395         bs_read1( &s ); /* low_delay */
 396
 397         if( bs_read1( &s ) )
 398         {
 399             bs_skip( &s, 16 );
 400             bs_skip( &s, 16 );
 401             bs_skip( &s, 16 );
 402             bs_skip( &s, 3 );
 403             bs_skip( &s, 11 );
 404             bs_skip( &s, 1 );
 405             bs_skip( &s, 16 );
 406         }
 407     }
 408     /* shape 0->RECT, 1->BIN, 2->BIN_ONLY, 3->GRAY */
 409     i_shape = bs_read( &s, 2 );
 410     if( i_shape == 3 && i_vo_ver_id != 1 )
 411     {
 412         bs_skip( &s, 4 );
 413     }
 414
 415     if( !bs_read1( &s ) ) return VLC_EGENERIC; /* Marker */
 416
 417     p_sys->i_fps_num = bs_read( &s, 16 ); /* Time increment resolution*/
 418     if( !p_sys->i_fps_num ) p_sys->i_fps_num = 1;
 419
 420     if( !bs_read1( &s ) ) return VLC_EGENERIC; /* Marker */
 421
 422     if( bs_read1( &s ) )
 423     {
 424         int i_time_increment_bits = vlc_log2( p_sys->i_fps_num - 1 ) + 1;
 425
 426         if( i_time_increment_bits < 1 ) i_time_increment_bits = 1;
 427
 428         p_sys->i_fps_den = bs_read( &s, i_time_increment_bits );
 429     }
 430     if( i_shape == 0 )
 431     {
 432         bs_skip( &s, 1 );
 433         fmt->video.i_width = bs_read( &s, 13 );
 434         bs_skip( &s, 1 );
 435         fmt->video.i_height= bs_read( &s, 13 );
 436         bs_skip( &s, 1 );
 437     }
 438
 439     return VLC_SUCCESS;
 440 }
 441
 442 static int ParseVO( decoder_t *p_dec, block_t *p_vo )
 443 {
 444     bs_t s;
 445     bs_init( &s, &p_vo->p_buffer[4], p_vo->i_buffer - 4 );
 446     if( bs_read1( &s ) )
 447         bs_skip( &s, 7 );
 448
 449     const uint8_t visual_object_type = bs_read( &s, 4 );
 450     if( visual_object_type == 1 /* video ID */ ||
 451         visual_object_type == 2 /* still texture ID */ )
 452     {
 453         uint8_t colour_primaries = 1;
 454         uint8_t colour_xfer = 1;
 455         uint8_t colour_matrix_coeff = 1;
 456         uint8_t full_range = 0;
 457         if( bs_read1( &s ) ) /* video_signal_type */
 458         {
 459             bs_read( &s, 3 );
 460             full_range = bs_read( &s, 1 );
 461             if( bs_read( &s, 1 ) ) /* colour description */
 462             {
 463                 colour_primaries = bs_read( &s, 8 );
 464                 colour_xfer = bs_read( &s, 8 );
 465                 colour_matrix_coeff = bs_read( &s, 8 );
 466             }
 467         }
 468
 469         if( p_dec->fmt_in.video.primaries == COLOR_PRIMARIES_UNDEF )
 470         {
 471             p_dec->fmt_out.video.primaries = hxxx_colour_primaries_to_vlc( colour_primaries );
 472             p_dec->fmt_out.video.transfer = hxxx_transfer_characteristics_to_vlc( colour_xfer );
 473             p_dec->fmt_out.video.space = hxxx_matrix_coeffs_to_vlc( colour_matrix_coeff );
 474             p_dec->fmt_out.video.b_color_range_full = full_range;
 475         }
 476     }
 477
 478     return VLC_SUCCESS;
 479 }
 480
 481 static int ParseVOP( decoder_t *p_dec, block_t *p_vop )
 482 {
 483     decoder_sys_t *p_sys = p_dec->p_sys;
 484     int64_t i_time_increment, i_time_ref;
 485     int i_modulo_time_base = 0, i_time_increment_bits;
 486     bs_t s;
 487
 488     bs_init( &s, &p_vop->p_buffer[4], p_vop->i_buffer - 4 );
 489
 490     switch( bs_read( &s, 2 ) )
 491     {
 492     case 0:
 493         p_sys->i_flags = BLOCK_FLAG_TYPE_I;
 494         break;
 495     case 1:
 496         p_sys->i_flags = BLOCK_FLAG_TYPE_P;
 497         break;
 498     case 2:
 499         p_sys->i_flags = BLOCK_FLAG_TYPE_B;
 500         p_sys->b_frame = true;
 501         break;
 502     case 3: /* gni ? */
 503         p_sys->i_flags = BLOCK_FLAG_TYPE_PB;
 504         break;
 505     }
 506
 507     while( bs_read( &s, 1 ) ) i_modulo_time_base++;
 508     if( !bs_read1( &s ) ) return VLC_EGENERIC; /* Marker */
 509
 510     /* VOP time increment */
 511     i_time_increment_bits = vlc_log2(p_dec->p_sys->i_fps_num - 1) + 1;
 512     if( i_time_increment_bits < 1 ) i_time_increment_bits = 1;
 513     i_time_increment = bs_read( &s, i_time_increment_bits );
 514
 515     /* Interpolate PTS/DTS */
 516     if( !(p_sys->i_flags & BLOCK_FLAG_TYPE_B) )
 517     {
 518         p_sys->i_last_time_ref = p_sys->i_time_ref;
 519         p_sys->i_time_ref +=
 520             (i_modulo_time_base * p_dec->p_sys->i_fps_num);
 521         i_time_ref = p_sys->i_time_ref;
 522     }
 523     else
 524     {
 525         i_time_ref = p_sys->i_last_time_ref +
 526             (i_modulo_time_base * p_dec->p_sys->i_fps_num);
 527     }
 528
 529 #if 0
 530     msg_Err( p_dec, "interp pts/dts (%lli,%lli), pts/dts (%lli,%lli)",
 531              p_sys->i_interpolated_pts, p_sys->i_interpolated_dts,
 532              p_vop->i_pts, p_vop->i_dts );
 533 #endif
 534
 535     if( p_dec->p_sys->i_fps_num < 5 && /* Work-around buggy streams */
 536         p_dec->fmt_in.video.i_frame_rate > 0 &&
 537         p_dec->fmt_in.video.i_frame_rate_base > 0 )
 538     {
 539         p_sys->i_interpolated_pts += CLOCK_FREQ *
 540         p_dec->fmt_in.video.i_frame_rate_base /
 541         p_dec->fmt_in.video.i_frame_rate;
 542     }
 543     else if( p_dec->p_sys->i_fps_num )
 544         p_sys->i_interpolated_pts +=
 545             ( CLOCK_FREQ * (i_time_ref + i_time_increment -
 546               p_sys->i_last_time - p_sys->i_last_timeincr) /
 547               p_dec->p_sys->i_fps_num );
 548
 549     p_sys->i_last_time = i_time_ref;
 550     p_sys->i_last_timeincr = i_time_increment;
 551
 552     /* Correct interpolated dts when we receive a new pts/dts */
 553     if( p_vop->i_pts > VLC_TS_INVALID )
 554         p_sys->i_interpolated_pts = p_vop->i_pts;
 555     if( p_vop->i_dts > VLC_TS_INVALID )
 556         p_sys->i_interpolated_dts = p_vop->i_dts;
 557
 558     if( (p_sys->i_flags & BLOCK_FLAG_TYPE_B) || !p_sys->b_frame )
 559     {
 560         /* Trivial case (DTS == PTS) */
 561
 562         p_sys->i_interpolated_dts = p_sys->i_interpolated_pts;
 563
 564         if( p_vop->i_pts > VLC_TS_INVALID )
 565             p_sys->i_interpolated_dts = p_vop->i_pts;
 566         if( p_vop->i_dts > VLC_TS_INVALID )
 567             p_sys->i_interpolated_dts = p_vop->i_dts;
 568
 569         p_sys->i_interpolated_pts = p_sys->i_interpolated_dts;
 570     }
 571     else
 572     {
 573         if( p_sys->i_last_ref_pts > VLC_TS_INVALID )
 574             p_sys->i_interpolated_dts = p_sys->i_last_ref_pts;
 575
 576         p_sys->i_last_ref_pts = p_sys->i_interpolated_pts;
 577     }
 578
 579     return VLC_SUCCESS;
 580 }
 581
 582 /* look at libavutil av_log2 ;) */
 583 static int vlc_log2( unsigned int v )
 584 {
 585     int n = 0;
 586     static const int vlc_log2_table[16] =
 587     {
 588         0,0,1,1,2,2,2,2, 3,3,3,3,3,3,3,3
 589     };
 590
 591     if( v&0xffff0000 )
 592     {
 593         v >>= 16;
 594         n += 16;
 595     }
 596     if( v&0xff00 )
 597     {
 598         v >>= 8;
 599         n += 8;
 600     }
 601     if( v&0xf0 )
 602     {
 603         v >>= 4;
 604         n += 4;
 605     }
 606     n += vlc_log2_table[v];
 607
 608     return n;
 609 }