git.sesse.net Git - vlc/blob - plugins/mpeg_vdec/vpar_synchro.c

   1 /*****************************************************************************
   2  * vpar_synchro.c : frame dropping routines
   3  *****************************************************************************
   4  * Copyright (C) 1999-2001 VideoLAN
   5  * $Id: vpar_synchro.c,v 1.5 2001/12/30 07:09:56 sam Exp $
   6  *
   7  * Authors: Christophe Massiot <massiot@via.ecp.fr>
   8  *          Samuel Hocevar <sam@via.ecp.fr>
   9  *          Jean-Marc Dressler <polux@via.ecp.fr>
  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., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
  24  *****************************************************************************/
  25
  26 /*
  27  * DISCUSSION : How to Write an efficient Frame-Dropping Algorithm
  28  * ==========
  29  *
  30  * This implementation is based on mathematical and statistical
  31  * developments. Older implementations used an enslavement, considering
  32  * that if we're late when reading an I picture, we will decode one frame
  33  * less. It had a tendancy to derive, and wasn't responsive enough, which
  34  * would have caused trouble with the stream control stuff.
  35  *
  36  * 1. Structure of a picture stream
  37  *    =============================
  38  * Between 2 I's, we have for instance :
  39  *    I   B   P   B   P   B   P   B   P   B   P   B   I
  40  *    t0  t1  t2  t3  t4  t5  t6  t7  t8  t9  t10 t11 t12
  41  * Please bear in mind that B's and IP's will be inverted when displaying
  42  * (decoding order != presentation order). Thus, t1 < t0.
  43  *
  44  * 2. Definitions
  45  *    ===========
  46  * t[0..12]     : Presentation timestamps of pictures 0..12.
  47  * t            : Current timestamp, at the moment of the decoding.
  48  * T            : Picture period, T = 1/frame_rate.
  49  * tau[I,P,B]   : Mean time to decode an [I,P,B] picture.
  50  * tauYUV       : Mean time to render a picture (given by the video_output).
  51  * tau´[I,P,B] = 2 * tau[I,P,B] + tauYUV
  52  *              : Mean time + typical difference (estimated to tau/2, that
  53  *                needs to be confirmed) + render time.
  54  * DELTA        : A given error margin.
  55  *
  56  * 3. General considerations
  57  *    ======================
  58  * We define three types of machines :
  59  *      14T > tauI : machines capable of decoding all I pictures
  60  *      2T > tauP  : machines capable of decoding all P pictures
  61  *      T > tauB   : machines capable of decoding all B pictures
  62  *
  63  * 4. Decoding of an I picture
  64  *    ========================
  65  * On fast machines, we decode all I's.
  66  * Otherwise :
  67  * We can decode an I picture if we simply have enough time to decode it
  68  * before displaying :
  69  *      t0 - t > tau´I + DELTA
  70  *
  71  * 5. Decoding of a P picture
  72  *    =======================
  73  * On fast machines, we decode all P's.
  74  * Otherwise :
  75  * First criterion : have time to decode it.
  76  *      t2 - t > tau´P + DELTA
  77  *
  78  * Second criterion : it shouldn't prevent us from displaying the forthcoming
  79  * I picture, which is more important.
  80  *      t12 - t > tau´P + tau´I + DELTA
  81  *
  82  * 6. Decoding of a B picture
  83  *    =======================
  84  * On fast machines, we decode all B's. Otherwise :
  85  *      t1 - t > tau´B + DELTA
  86  * Since the next displayed I or P is already decoded, we don't have to
  87  * worry about it.
  88  *
  89  * I hope you will have a pleasant flight and do not forget your life
  90  * jacket.
  91  *                                                  --Meuuh (2000-12-29)
  92  */
  93
  94 /*****************************************************************************
  95  * Preamble
  96  *****************************************************************************/
  97 #include <string.h>                                    /* memcpy(), memset() */
  98
  99 #include <videolan/vlc.h>
 100
 101 #include "video.h"
 102 #include "video_output.h"
 103
 104 #include "stream_control.h"
 105 #include "input_ext-dec.h"
 106
 107 #include "vdec_ext-plugins.h"
 108 #include "vpar_pool.h"
 109 #include "video_parser.h"
 110
 111 /*
 112  * Local prototypes
 113  */
 114 static int  SynchroType( void );
 115
 116 /* Error margins */
 117 #define DELTA                   (int)(0.075*CLOCK_FREQ)
 118
 119 #define DEFAULT_NB_P            5
 120 #define DEFAULT_NB_B            1
 121
 122 /*****************************************************************************
 123  * vpar_SynchroInit : You know what ?
 124  *****************************************************************************/
 125 void vpar_SynchroInit( vpar_thread_t * p_vpar )
 126 {
 127     p_vpar->synchro.i_type = SynchroType();
 128
 129     /* We use a fake stream pattern, which is often right. */
 130     p_vpar->synchro.i_n_p = p_vpar->synchro.i_eta_p = DEFAULT_NB_P;
 131     p_vpar->synchro.i_n_b = p_vpar->synchro.i_eta_b = DEFAULT_NB_B;
 132     memset( p_vpar->synchro.p_tau, 0, 4 * sizeof(mtime_t) );
 133     memset( p_vpar->synchro.pi_meaningful, 0, 4 * sizeof(unsigned int) );
 134     p_vpar->synchro.b_dropped_last = 0;
 135     p_vpar->synchro.current_pts = mdate() + DEFAULT_PTS_DELAY;
 136     p_vpar->synchro.backward_pts = 0;
 137     p_vpar->synchro.i_current_period = p_vpar->synchro.i_backward_period = 0;
 138     p_vpar->synchro.i_trashed_pic = p_vpar->synchro.i_not_chosen_pic =
 139         p_vpar->synchro.i_pic = 0;
 140 }
 141
 142 /*****************************************************************************
 143  * vpar_SynchroChoose : Decide whether we will decode a picture or not
 144  *****************************************************************************/
 145 boolean_t vpar_SynchroChoose( vpar_thread_t * p_vpar, int i_coding_type,
 146                               int i_structure )
 147 {
 148     /* For clarity reasons, we separated the special synchros code from the
 149      * mathematical synchro */
 150
 151     if( p_vpar->synchro.i_type != VPAR_SYNCHRO_DEFAULT )
 152     {
 153         switch( i_coding_type )
 154         {
 155         case I_CODING_TYPE:
 156             /* I, IP, IP+, IPB */
 157             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_Iplus )
 158             {
 159                 p_vpar->synchro.b_dropped_last = 1;
 160             }
 161             return( 1 );
 162
 163         case P_CODING_TYPE:
 164             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_I ) /* I */
 165             {
 166                 return( 0 );
 167             }
 168
 169             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_Iplus ) /* I+ */
 170             {
 171                 if( p_vpar->synchro.b_dropped_last )
 172                 {
 173                     p_vpar->synchro.b_dropped_last = 0;
 174                     return( 1 );
 175                 }
 176                 else
 177                 {
 178                     return( 0 );
 179                 }
 180             }
 181
 182             return( 1 ); /* IP, IP+, IPB */
 183
 184         case B_CODING_TYPE:
 185             if( p_vpar->synchro.i_type <= VPAR_SYNCHRO_IP ) /* I, IP */
 186             {
 187                 return( 0 );
 188             }
 189             else if( p_vpar->synchro.i_type == VPAR_SYNCHRO_IPB ) /* IPB */
 190             {
 191                 return( 1 );
 192             }
 193
 194             p_vpar->synchro.b_dropped_last ^= 1; /* IP+ */
 195             return( !p_vpar->synchro.b_dropped_last );
 196         }
 197         return( 0 ); /* never reached but gcc yells at me */
 198     }
 199     else
 200     {
 201 #define TAU_PRIME( coding_type )    (p_vpar->synchro.p_tau[(coding_type)] \
 202                                  + (p_vpar->synchro.p_tau[(coding_type)] >> 1) \
 203                                             + tau_yuv)
 204 #define S                           p_vpar->synchro
 205         /* VPAR_SYNCHRO_DEFAULT */
 206         mtime_t         now, period, tau_yuv;
 207         mtime_t         pts = 0;
 208         boolean_t       b_decode = 0;
 209 #ifdef TRACE_VPAR
 210         char            p_date[MSTRTIME_MAX_SIZE];
 211 #endif
 212
 213         now = mdate();
 214         period = 1000000 * 1001 / p_vpar->sequence.i_frame_rate
 215                     * p_vpar->sequence.i_current_rate / DEFAULT_RATE;
 216
 217         vlc_mutex_lock( &p_vpar->p_vout->change_lock );
 218         tau_yuv = p_vpar->p_vout->render_time;
 219         vlc_mutex_unlock( &p_vpar->p_vout->change_lock );
 220
 221         switch( i_coding_type )
 222         {
 223         case I_CODING_TYPE:
 224             if( S.backward_pts )
 225             {
 226                 pts = S.backward_pts;
 227             }
 228             else
 229             {
 230                 /* displaying order : B B P B B I
 231                  *                      ^       ^
 232                  *                      |       +- current picture
 233                  *                      +- current PTS
 234                  */
 235                 pts = S.current_pts + period * (S.i_n_b + 2);
 236             }
 237
 238             if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
 239                     S.p_tau[I_CODING_TYPE] )
 240             {
 241                 b_decode = 1;
 242             }
 243             else
 244             {
 245                 b_decode = (pts - now) > (TAU_PRIME(I_CODING_TYPE) + DELTA);
 246             }
 247             if( !b_decode )
 248                 intf_WarnMsg( 1, "vpar synchro warning: trashing I (%lld)",
 249                              pts - now);
 250             break;
 251
 252         case P_CODING_TYPE:
 253             if( S.backward_pts )
 254             {
 255                 pts = S.backward_pts;
 256             }
 257             else
 258             {
 259                 pts = S.current_pts + period * (S.i_n_b + 1);
 260             }
 261
 262             if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
 263                     S.p_tau[I_CODING_TYPE] )
 264             {
 265                 if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
 266                 {
 267                     /* Security in case we're _really_ late */
 268                     b_decode = (pts - now > 0);
 269                 }
 270                 else
 271                 {
 272                     b_decode = (pts - now) > (TAU_PRIME(P_CODING_TYPE) + DELTA);
 273                     /* next I */
 274                     b_decode &= (pts - now
 275                                   + period
 276                               * ( (S.i_n_p - S.i_eta_p) * (1 + S.i_n_b) - 1 ))
 277                                 > (TAU_PRIME(P_CODING_TYPE)
 278                                     + TAU_PRIME(I_CODING_TYPE) + DELTA);
 279                 }
 280             }
 281             else
 282             {
 283                 b_decode = 0;
 284             }
 285             break;
 286
 287         case B_CODING_TYPE:
 288             pts = S.current_pts;
 289
 290             if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
 291             {
 292                 b_decode = (pts - now) > (TAU_PRIME(B_CODING_TYPE) + DELTA);
 293             }
 294             else
 295             {
 296                 b_decode = 0;
 297             }
 298         }
 299
 300 #ifdef TRACE_VPAR
 301         intf_DbgMsg("vpar synchro debug: %s picture scheduled for %s, %s (%lld)",
 302                     i_coding_type == B_CODING_TYPE ? "B" :
 303                     (i_coding_type == P_CODING_TYPE ? "P" : "I"),
 304                     mstrtime(p_date, pts), b_decode ? "decoding" : "trashed",
 305                     S.p_tau[i_coding_type]);
 306 #endif
 307         if( !b_decode )
 308         {
 309             S.i_not_chosen_pic++;
 310         }
 311         return( b_decode );
 312 #undef S
 313 #undef TAU_PRIME
 314     }
 315 }
 316
 317 /*****************************************************************************
 318  * vpar_SynchroTrash : Update counters when we trash a picture
 319  *****************************************************************************/
 320 void vpar_SynchroTrash( vpar_thread_t * p_vpar, int i_coding_type,
 321                         int i_structure )
 322 {
 323     p_vpar->synchro.i_trashed_pic++;
 324 }
 325
 326 /*****************************************************************************
 327  * vpar_SynchroDecode : Update timers when we decide to decode a picture
 328  *****************************************************************************/
 329 void vpar_SynchroDecode( vpar_thread_t * p_vpar, int i_coding_type,
 330                          int i_structure )
 331 {
 332     p_vpar->synchro.decoding_start = mdate();
 333 }
 334
 335 /*****************************************************************************
 336  * vpar_SynchroEnd : Called when the image is totally decoded
 337  *****************************************************************************/
 338 void vpar_SynchroEnd( vpar_thread_t * p_vpar, int i_coding_type,
 339                       int i_structure, int i_garbage )
 340 {
 341     mtime_t     tau;
 342
 343     if( !i_garbage )
 344     {
 345         tau = mdate() - p_vpar->synchro.decoding_start;
 346
 347         /* If duration too high, something happened (pause ?), so don't
 348          * take it into account. */
 349         if( tau < 3 * p_vpar->synchro.p_tau[i_coding_type]
 350              || !p_vpar->synchro.pi_meaningful[i_coding_type] )
 351         {
 352             /* Mean with average tau, to ensure stability. */
 353             p_vpar->synchro.p_tau[i_coding_type] =
 354                 (p_vpar->synchro.pi_meaningful[i_coding_type]
 355                  * p_vpar->synchro.p_tau[i_coding_type] + tau)
 356                 / (p_vpar->synchro.pi_meaningful[i_coding_type] + 1);
 357             if( p_vpar->synchro.pi_meaningful[i_coding_type] < MAX_PIC_AVERAGE )
 358             {
 359                 p_vpar->synchro.pi_meaningful[i_coding_type]++;
 360             }
 361         }
 362
 363 #ifdef TRACE_VPAR
 364         intf_DbgMsg("vpar synchro debug: finished decoding %s (%lld)",
 365                     i_coding_type == B_CODING_TYPE ? "B" :
 366                     (i_coding_type == P_CODING_TYPE ? "P" : "I"), tau);
 367 #endif
 368     }
 369     else
 370     {
 371         intf_DbgMsg("vpar synchro debug: aborting %s",
 372                     i_coding_type == B_CODING_TYPE ? "B" :
 373                     (i_coding_type == P_CODING_TYPE ? "P" : "I"));
 374     }
 375 }
 376
 377 /*****************************************************************************
 378  * vpar_SynchroDate : When an image has been decoded, ask for its date
 379  *****************************************************************************/
 380 mtime_t vpar_SynchroDate( vpar_thread_t * p_vpar )
 381 {
 382     /* No need to lock, since PTS are only used by the video parser. */
 383     return( p_vpar->synchro.current_pts );
 384 }
 385
 386 /*****************************************************************************
 387  * vpar_SynchroNewPicture: Update stream structure and PTS
 388  *****************************************************************************/
 389 void vpar_SynchroNewPicture( vpar_thread_t * p_vpar, int i_coding_type,
 390                              int i_repeat_field )
 391 {
 392     mtime_t         period = 1000000 * 1001 / p_vpar->sequence.i_frame_rate
 393                               * p_vpar->sequence.i_current_rate / DEFAULT_RATE;
 394 #if 0
 395     mtime_t         now = mdate();
 396 #endif
 397
 398     switch( i_coding_type )
 399     {
 400     case I_CODING_TYPE:
 401         if( p_vpar->synchro.i_eta_p
 402              && p_vpar->synchro.i_eta_p != p_vpar->synchro.i_n_p )
 403         {
 404             intf_WarnMsg( 3, "vpar info: stream periodicity changed "
 405                           "from P[%d] to P[%d]",
 406                           p_vpar->synchro.i_n_p, p_vpar->synchro.i_eta_p );
 407             p_vpar->synchro.i_n_p = p_vpar->synchro.i_eta_p;
 408         }
 409         p_vpar->synchro.i_eta_p = p_vpar->synchro.i_eta_b = 0;
 410
 411         if( p_main->b_stats && p_vpar->synchro.i_type == VPAR_SYNCHRO_DEFAULT )
 412         {
 413             intf_Msg( "vpar synchro stats: I(%lld) P(%lld)[%d] B(%lld)[%d] YUV(%lld) : trashed %d:%d/%d",
 414                   p_vpar->synchro.p_tau[I_CODING_TYPE],
 415                   p_vpar->synchro.p_tau[P_CODING_TYPE],
 416                   p_vpar->synchro.i_n_p,
 417                   p_vpar->synchro.p_tau[B_CODING_TYPE],
 418                   p_vpar->synchro.i_n_b,
 419                   p_vpar->p_vout->render_time,
 420                   p_vpar->synchro.i_not_chosen_pic,
 421                   p_vpar->synchro.i_trashed_pic -
 422                   p_vpar->synchro.i_not_chosen_pic,
 423                   p_vpar->synchro.i_pic );
 424             p_vpar->synchro.i_trashed_pic = p_vpar->synchro.i_not_chosen_pic
 425                 = p_vpar->synchro.i_pic = 0;
 426         }
 427         break;
 428
 429     case P_CODING_TYPE:
 430         p_vpar->synchro.i_eta_p++;
 431         if( p_vpar->synchro.i_eta_b
 432              && p_vpar->synchro.i_eta_b != p_vpar->synchro.i_n_b )
 433         {
 434             intf_WarnMsg( 3, "vpar info: stream periodicity changed "
 435                           "from B[%d] to B[%d]",
 436                           p_vpar->synchro.i_n_b, p_vpar->synchro.i_eta_b );
 437             p_vpar->synchro.i_n_b = p_vpar->synchro.i_eta_b;
 438         }
 439         p_vpar->synchro.i_eta_b = 0;
 440         break;
 441     case B_CODING_TYPE:
 442         p_vpar->synchro.i_eta_b++;
 443         break;
 444     }
 445
 446     p_vpar->synchro.current_pts += p_vpar->synchro.i_current_period
 447                                         * (period >> 1);
 448
 449 #define PTS_THRESHOLD   (period >> 2)
 450     if( i_coding_type == B_CODING_TYPE )
 451     {
 452         /* A video frame can be displayed 1, 2 or 3 times, according to
 453          * repeat_first_field, top_field_first, progressive_sequence and
 454          * progressive_frame. */
 455         p_vpar->synchro.i_current_period = i_repeat_field;
 456
 457         if( p_vpar->sequence.next_pts )
 458         {
 459             if( p_vpar->sequence.next_pts - p_vpar->synchro.current_pts
 460                     > PTS_THRESHOLD
 461                  || p_vpar->synchro.current_pts - p_vpar->sequence.next_pts
 462                     > PTS_THRESHOLD )
 463             {
 464                 intf_WarnMsg( 2,
 465                         "vpar synchro warning: pts != current_date (%lld)",
 466                         p_vpar->synchro.current_pts
 467                             - p_vpar->sequence.next_pts );
 468             }
 469             p_vpar->synchro.current_pts = p_vpar->sequence.next_pts;
 470             p_vpar->sequence.next_pts = 0;
 471         }
 472     }
 473     else
 474     {
 475         p_vpar->synchro.i_current_period = p_vpar->synchro.i_backward_period;
 476         p_vpar->synchro.i_backward_period = i_repeat_field;
 477
 478         if( p_vpar->synchro.backward_pts )
 479         {
 480             if( p_vpar->sequence.next_dts &&
 481                 (p_vpar->sequence.next_dts - p_vpar->synchro.backward_pts
 482                     > PTS_THRESHOLD
 483               || p_vpar->synchro.backward_pts - p_vpar->sequence.next_dts
 484                     > PTS_THRESHOLD) )
 485             {
 486                 intf_WarnMsg( 2,
 487                         "vpar synchro warning: backward_pts != dts (%lld)",
 488                         p_vpar->sequence.next_dts
 489                             - p_vpar->synchro.backward_pts );
 490             }
 491             if( p_vpar->synchro.backward_pts - p_vpar->synchro.current_pts
 492                     > PTS_THRESHOLD
 493                  || p_vpar->synchro.current_pts - p_vpar->synchro.backward_pts
 494                     > PTS_THRESHOLD )
 495             {
 496                 intf_WarnMsg( 2,
 497                    "vpar synchro warning: backward_pts != current_pts (%lld)",
 498                    p_vpar->synchro.current_pts - p_vpar->synchro.backward_pts );
 499             }
 500             p_vpar->synchro.current_pts = p_vpar->synchro.backward_pts;
 501             p_vpar->synchro.backward_pts = 0;
 502         }
 503         else if( p_vpar->sequence.next_dts )
 504         {
 505             if( p_vpar->sequence.next_dts - p_vpar->synchro.current_pts
 506                     > PTS_THRESHOLD
 507                  || p_vpar->synchro.current_pts - p_vpar->sequence.next_dts
 508                     > PTS_THRESHOLD )
 509             {
 510                 intf_WarnMsg( 2,
 511                         "vpar synchro warning: dts != current_pts (%lld)",
 512                         p_vpar->synchro.current_pts
 513                             - p_vpar->sequence.next_dts );
 514             }
 515             /* By definition of a DTS. */
 516             p_vpar->synchro.current_pts = p_vpar->sequence.next_dts;
 517             p_vpar->sequence.next_dts = 0;
 518         }
 519
 520         if( p_vpar->sequence.next_pts )
 521         {
 522             /* Store the PTS for the next time we have to date an I picture. */
 523             p_vpar->synchro.backward_pts = p_vpar->sequence.next_pts;
 524             p_vpar->sequence.next_pts = 0;
 525         }
 526     }
 527 #undef PTS_THRESHOLD
 528
 529 #if 0
 530     /* Removed for incompatibility with slow motion */
 531     if( p_vpar->synchro.current_pts + DEFAULT_PTS_DELAY < now )
 532     {
 533         /* We cannot be _that_ late, something must have happened, reinit
 534          * the dates. */
 535         intf_WarnMsg( 2, "PTS << now (%lld), resetting",
 536                       now - p_vpar->synchro.current_pts - DEFAULT_PTS_DELAY );
 537         p_vpar->synchro.current_pts = now + DEFAULT_PTS_DELAY;
 538     }
 539     if( p_vpar->synchro.backward_pts
 540          && p_vpar->synchro.backward_pts + DEFAULT_PTS_DELAY < now )
 541     {
 542         /* The same. */
 543         p_vpar->synchro.backward_pts = 0;
 544     }
 545 #endif
 546
 547     p_vpar->synchro.i_pic++;
 548 }
 549
 550 /*****************************************************************************
 551  * SynchroType: Get the user's synchro type
 552  *****************************************************************************
 553  * This function is called at initialization.
 554  *****************************************************************************/
 555 static int SynchroType( void )
 556 {
 557     char * psz_synchro = main_GetPszVariable( VPAR_SYNCHRO_VAR, NULL );
 558
 559     if( psz_synchro == NULL )
 560     {
 561         return VPAR_SYNCHRO_DEFAULT;
 562     }
 563
 564     switch( *psz_synchro++ )
 565     {
 566       case 'i':
 567       case 'I':
 568         switch( *psz_synchro++ )
 569         {
 570           case '\0':
 571             return VPAR_SYNCHRO_I;
 572
 573           case '+':
 574             if( *psz_synchro ) return 0;
 575             return VPAR_SYNCHRO_Iplus;
 576
 577           case 'p':
 578           case 'P':
 579             switch( *psz_synchro++ )
 580             {
 581               case '\0':
 582                 return VPAR_SYNCHRO_IP;
 583
 584               case '+':
 585                 if( *psz_synchro ) return 0;
 586                 return VPAR_SYNCHRO_IPplus;
 587
 588               case 'b':
 589               case 'B':
 590                 if( *psz_synchro ) return 0;
 591                 return VPAR_SYNCHRO_IPB;
 592
 593               default:
 594                 return VPAR_SYNCHRO_DEFAULT;
 595
 596             }
 597
 598           default:
 599             return VPAR_SYNCHRO_DEFAULT;
 600         }
 601     }
 602
 603     return VPAR_SYNCHRO_DEFAULT;
 604 }
 605