git.sesse.net Git - vlc/blob - src/video_parser/vpar_synchro.c

   1 /*****************************************************************************
   2  * vpar_synchro.c : frame dropping routines
   3  *****************************************************************************
   4  * Copyright (C) 1999, 2000 VideoLAN
   5  * $Id: vpar_synchro.c,v 1.70 2001/01/10 19:48:26 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  * FIXME: write a few words about stream structure changes.
  45  *
  46  * 2. Definitions
  47  *    ===========
  48  * t[0..12]     : Presentation timestamps of pictures 0..12.
  49  * t            : Current timestamp, at the moment of the decoding.
  50  * T            : Picture period, T = 1/frame_rate.
  51  * tau[I,P,B]   : Mean time to decode an [I,P,B] picture.
  52  * tauYUV       : Mean time to render a picture (given by the video_output).
  53  * tau´[I,P,B] = 2 * tau[I,P,B] + tauYUV
  54  *              : Mean time + typical difference (estimated to tau/2, that
  55  *                needs to be confirmed) + render time.
  56  * DELTA        : A given error margin.
  57  *
  58  * 3. General considerations
  59  *    ======================
  60  * We define three types of machines :
  61  *      14T > tauI : machines capable of decoding all I pictures
  62  *      2T > tauP  : machines capable of decoding all P pictures
  63  *      T > tauB   : machines capable of decoding all B pictures
  64  *
  65  * 4. Decoding of an I picture
  66  *    ========================
  67  * On fast machines, we decode all I's.
  68  * Otherwise :
  69  * We can decode an I picture if we simply have enough time to decode it
  70  * before displaying :
  71  *      t0 - t > tau´I + DELTA
  72  *
  73  * 5. Decoding of a P picture
  74  *    =======================
  75  * On fast machines, we decode all P's.
  76  * Otherwise :
  77  * First criterion : have time to decode it.
  78  *      t2 - t > tau´P + DELTA
  79  *
  80  * Second criterion : it shouldn't prevent us from displaying the forthcoming
  81  * I picture, which is more important.
  82  *      t12 - t > tau´P + tau´I + DELTA
  83  *
  84  * 6. Decoding of a B picture
  85  *    =======================
  86  * On fast machines, we decode all B's. Otherwise :
  87  *      t1 - t > tau´B + DELTA
  88  * Since the next displayed I or P is already decoded, we don't have to
  89  * worry about it.
  90  *
  91  * I hope you will have a pleasant flight and do not forget your life
  92  * jacket.
  93  *                                                  --Meuuh (2000-12-29)
  94  */
  95
  96 /*****************************************************************************
  97  * Preamble
  98  *****************************************************************************/
  99 #include "defs.h"
 100
 101 #include "config.h"
 102 #include "common.h"
 103 #include "threads.h"
 104 #include "mtime.h"
 105 #include "plugins.h"
 106
 107 #include "intf_msg.h"
 108
 109 #include "stream_control.h"
 110 #include "input_ext-dec.h"
 111
 112 #include "video.h"
 113 #include "video_output.h"
 114
 115 #include "../video_decoder/vdec_idct.h"
 116 #include "../video_decoder/video_decoder.h"
 117 #include "../video_decoder/vdec_motion.h"
 118
 119 #include "../video_decoder/vpar_blocks.h"
 120 #include "../video_decoder/vpar_headers.h"
 121 #include "../video_decoder/vpar_synchro.h"
 122 #include "../video_decoder/video_parser.h"
 123
 124 #include "main.h"
 125
 126 /*
 127  * Local prototypes
 128  */
 129 static int  SynchroType( void );
 130
 131 /* Error margins */
 132 #define DELTA                   (int)(0.040*CLOCK_FREQ)
 133 #define PTS_THRESHOLD           (int)(0.030*CLOCK_FREQ)
 134
 135 #define DEFAULT_NB_P            5
 136 #define DEFAULT_NB_B            1
 137
 138 /*****************************************************************************
 139  * vpar_SynchroInit : You know what ?
 140  *****************************************************************************/
 141 void vpar_SynchroInit( vpar_thread_t * p_vpar )
 142 {
 143     p_vpar->synchro.i_type = SynchroType();
 144     p_vpar->synchro.i_start = p_vpar->synchro.i_end = 0;
 145     vlc_mutex_init( &p_vpar->synchro.fifo_lock );
 146
 147     /* We use a fake stream pattern, which is often right. */
 148     p_vpar->synchro.i_n_p = p_vpar->synchro.i_eta_p = DEFAULT_NB_P;
 149     p_vpar->synchro.i_n_b = p_vpar->synchro.i_eta_b = DEFAULT_NB_B;
 150     memset( p_vpar->synchro.p_tau, 0, 4 * sizeof(mtime_t) );
 151     memset( p_vpar->synchro.pi_meaningful, 0, 4 * sizeof(unsigned int) );
 152     p_vpar->synchro.b_dropped_last = 0;
 153     p_vpar->synchro.current_pts = mdate() + DEFAULT_PTS_DELAY;
 154     p_vpar->synchro.backward_pts = 0;
 155 #ifdef STATS
 156     p_vpar->synchro.i_trashed_pic = p_vpar->synchro.i_not_chosen_pic =
 157         p_vpar->synchro.i_pic = 0;
 158 #endif
 159 }
 160
 161 /*****************************************************************************
 162  * vpar_SynchroChoose : Decide whether we will decode a picture or not
 163  *****************************************************************************/
 164 boolean_t vpar_SynchroChoose( vpar_thread_t * p_vpar, int i_coding_type,
 165                               int i_structure )
 166 {
 167     /* For clarity reasons, we separated the special synchros code from the
 168      * mathematical synchro */
 169
 170     if( p_vpar->synchro.i_type != VPAR_SYNCHRO_DEFAULT )
 171     {
 172         switch( i_coding_type )
 173         {
 174         case I_CODING_TYPE:
 175             /* I, IP, IP+, IPB */
 176             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_Iplus )
 177             {
 178                 p_vpar->synchro.b_dropped_last = 1;
 179             }
 180             return( 1 );
 181
 182         case P_CODING_TYPE:
 183             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_I ) /* I */
 184             {
 185                 return( 0 );
 186             }
 187
 188             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_Iplus ) /* I+ */
 189             {
 190                 if( p_vpar->synchro.b_dropped_last )
 191                 {
 192                     p_vpar->synchro.b_dropped_last = 0;
 193                     return( 1 );
 194                 }
 195                 else
 196                 {
 197                     return( 0 );
 198                 }
 199             }
 200
 201             return( 1 ); /* IP, IP+, IPB */
 202
 203         case B_CODING_TYPE:
 204             if( p_vpar->synchro.i_type <= VPAR_SYNCHRO_IP ) /* I, IP */
 205             {
 206                 return( 0 );
 207             }
 208             else if( p_vpar->synchro.i_type == VPAR_SYNCHRO_IPB ) /* IPB */
 209             {
 210                 return( 1 );
 211             }
 212
 213             p_vpar->synchro.b_dropped_last ^= 1; /* IP+ */
 214             return( !p_vpar->synchro.b_dropped_last );
 215         }
 216         return( 0 ); /* never reached but gcc yells at me */
 217     }
 218     else
 219     {
 220 #define TAU_PRIME( coding_type )    (p_vpar->synchro.p_tau[(coding_type)] \
 221                                  + (p_vpar->synchro.p_tau[(coding_type)] >> 1) \
 222                                             + tau_yuv)
 223 #define S                           p_vpar->synchro
 224         /* VPAR_SYNCHRO_DEFAULT */
 225         mtime_t         now, pts, period, tau_yuv;
 226         boolean_t       b_decode = 0;
 227 #ifdef DEBUG_VPAR
 228         char            p_date[MSTRTIME_MAX_SIZE];
 229 #endif
 230
 231         now = mdate();
 232         period = 1000000 / (p_vpar->sequence.i_frame_rate) * 1001;
 233
 234         vlc_mutex_lock( &p_vpar->p_vout->change_lock );
 235         tau_yuv = p_vpar->p_vout->render_time;
 236         vlc_mutex_unlock( &p_vpar->p_vout->change_lock );
 237
 238         vlc_mutex_lock( &p_vpar->synchro.fifo_lock );
 239
 240         switch( i_coding_type )
 241         {
 242         case I_CODING_TYPE:
 243             if( S.backward_pts )
 244             {
 245                 pts = S.backward_pts;
 246             }
 247             else
 248             {
 249                 /* displaying order : B B P B B I
 250                  *                      ^       ^
 251                  *                      |       +- current picture
 252                  *                      +- current PTS
 253                  */
 254                 pts = S.current_pts + period * (S.i_n_b + 2);
 255             }
 256
 257             if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
 258                     S.p_tau[I_CODING_TYPE] )
 259             {
 260                 b_decode = 1;
 261             }
 262             else
 263             {
 264                 b_decode = (pts - now) > (TAU_PRIME(I_CODING_TYPE) + DELTA);
 265             }
 266             if( !b_decode )
 267                 intf_WarnMsg( 3, "vpar synchro warning: trashing I" );
 268             break;
 269
 270         case P_CODING_TYPE:
 271             if( S.backward_pts )
 272             {
 273                 pts = S.backward_pts;
 274             }
 275             else
 276             {
 277                 pts = S.current_pts + period * (S.i_n_b + 1);
 278             }
 279
 280             if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
 281                     S.p_tau[I_CODING_TYPE] )
 282             {
 283                 if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
 284                 {
 285                     /* Security in case we're _really_ late */
 286                     b_decode = (pts - now > 0);
 287                 }
 288                 else
 289                 {
 290                     b_decode = (pts - now) > (TAU_PRIME(P_CODING_TYPE) + DELTA);
 291                     /* next I */
 292                     b_decode &= (pts - now
 293                                   + period
 294                               * ( (S.i_n_p - S.i_eta_p) * (1 + S.i_n_b) - 1 ))
 295                                 > (TAU_PRIME(P_CODING_TYPE)
 296                                     + TAU_PRIME(I_CODING_TYPE) + DELTA);
 297                 }
 298             }
 299             else
 300             {
 301                 b_decode = 0;
 302             }
 303             break;
 304
 305         case B_CODING_TYPE:
 306             pts = S.current_pts;
 307
 308             if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
 309             {
 310                 b_decode = (pts - now) > (TAU_PRIME(B_CODING_TYPE) + DELTA);
 311             }
 312             else
 313             {
 314                 b_decode = 0;
 315             }
 316         }
 317
 318         vlc_mutex_unlock( &p_vpar->synchro.fifo_lock );
 319 #ifdef DEBUG_VPAR
 320         intf_DbgMsg("vpar synchro debug: %s picture scheduled for %s, %s (%lld)",
 321                     i_coding_type == B_CODING_TYPE ? "B" :
 322                     (i_coding_type == P_CODING_TYPE ? "P" : "I"),
 323                     mstrtime(p_date, pts), b_decode ? "decoding" : "trashed",
 324                     S.p_tau[i_coding_type]);
 325 #endif
 326 #ifdef STATS
 327         if( !b_decode )
 328         {
 329             S.i_not_chosen_pic++;
 330         }
 331 #endif
 332         return( b_decode );
 333 #undef S
 334 #undef TAU_PRIME
 335     }
 336 }
 337
 338 /*****************************************************************************
 339  * vpar_SynchroTrash : Update counters when we trash a picture
 340  *****************************************************************************/
 341 void vpar_SynchroTrash( vpar_thread_t * p_vpar, int i_coding_type,
 342                         int i_structure )
 343 {
 344 #ifdef STATS
 345     p_vpar->synchro.i_trashed_pic++;
 346 #endif
 347 }
 348
 349 /*****************************************************************************
 350  * vpar_SynchroDecode : Update timers when we decide to decode a picture
 351  *****************************************************************************/
 352 void vpar_SynchroDecode( vpar_thread_t * p_vpar, int i_coding_type,
 353                          int i_structure )
 354 {
 355     vlc_mutex_lock( &p_vpar->synchro.fifo_lock );
 356
 357     if( ((p_vpar->synchro.i_end + 1 - p_vpar->synchro.i_start)
 358             % MAX_DECODING_PIC) )
 359     {
 360         p_vpar->synchro.p_date_fifo[p_vpar->synchro.i_end] = mdate();
 361         p_vpar->synchro.pi_coding_types[p_vpar->synchro.i_end] = i_coding_type;
 362
 363         FIFO_INCREMENT( i_end );
 364     }
 365     else
 366     {
 367         /* FIFO full, panic() */
 368         intf_ErrMsg("vpar error: synchro fifo full, estimations will be biased");
 369     }
 370     vlc_mutex_unlock( &p_vpar->synchro.fifo_lock );
 371 }
 372
 373 /*****************************************************************************
 374  * vpar_SynchroEnd : Called when the image is totally decoded
 375  *****************************************************************************/
 376 void vpar_SynchroEnd( vpar_thread_t * p_vpar, int i_garbage )
 377 {
 378     mtime_t     tau;
 379     int         i_coding_type;
 380
 381     vlc_mutex_lock( &p_vpar->synchro.fifo_lock );
 382
 383     if (!i_garbage)
 384     {
 385         tau = mdate() - p_vpar->synchro.p_date_fifo[p_vpar->synchro.i_start];
 386         i_coding_type = p_vpar->synchro.pi_coding_types[p_vpar->synchro.i_start];
 387
 388         /* Mean with average tau, to ensure stability. */
 389         p_vpar->synchro.p_tau[i_coding_type] =
 390             (p_vpar->synchro.pi_meaningful[i_coding_type]
 391              * p_vpar->synchro.p_tau[i_coding_type] + tau)
 392             / (p_vpar->synchro.pi_meaningful[i_coding_type] + 1);
 393         if( p_vpar->synchro.pi_meaningful[i_coding_type] < MAX_PIC_AVERAGE )
 394         {
 395             p_vpar->synchro.pi_meaningful[i_coding_type]++;
 396         }
 397 #ifdef DEBUG_VPAR
 398         intf_DbgMsg("vpar synchro debug: finished decoding %s (%lld)",
 399                     i_coding_type == B_CODING_TYPE ? "B" :
 400                     (i_coding_type == P_CODING_TYPE ? "P" : "I"), tau);
 401 #endif
 402     }
 403
 404     FIFO_INCREMENT( i_start );
 405
 406     vlc_mutex_unlock( &p_vpar->synchro.fifo_lock );
 407 }
 408
 409 /*****************************************************************************
 410  * vpar_SynchroDate : When an image has been decoded, ask for its date
 411  *****************************************************************************/
 412 mtime_t vpar_SynchroDate( vpar_thread_t * p_vpar )
 413 {
 414     /* No need to lock, since PTS are only used by the video parser. */
 415     return( p_vpar->synchro.current_pts );
 416 }
 417
 418 /*****************************************************************************
 419  * vpar_SynchroNewPicture: Update stream structure and PTS
 420  *****************************************************************************/
 421 void vpar_SynchroNewPicture( vpar_thread_t * p_vpar, int i_coding_type,
 422                              boolean_t b_repeat_field )
 423 {
 424     pes_packet_t *  p_pes;
 425     mtime_t         period = 1000000 / (p_vpar->sequence.i_frame_rate) * 1001;
 426
 427     switch( i_coding_type )
 428     {
 429     case I_CODING_TYPE:
 430         if( p_vpar->synchro.i_eta_p
 431                 && p_vpar->synchro.i_eta_p != p_vpar->synchro.i_n_p )
 432         {
 433             intf_WarnMsg( 1, "Stream periodicity changed from P[%d] to P[%d]",
 434                           p_vpar->synchro.i_n_p, p_vpar->synchro.i_eta_p );
 435             p_vpar->synchro.i_n_p = p_vpar->synchro.i_eta_p;
 436         }
 437         p_vpar->synchro.i_eta_p = p_vpar->synchro.i_eta_b = 0;
 438 #ifdef STATS
 439         if( p_vpar->synchro.i_type == VPAR_SYNCHRO_DEFAULT )
 440         {
 441             intf_Msg( "vpar synchro stats: I(%lld) P(%lld)[%d] B(%lld)[%d] YUV(%lld) : trashed %d:%d/%d",
 442                   p_vpar->synchro.p_tau[I_CODING_TYPE],
 443                   p_vpar->synchro.p_tau[P_CODING_TYPE],
 444                   p_vpar->synchro.i_n_p,
 445                   p_vpar->synchro.p_tau[B_CODING_TYPE],
 446                   p_vpar->synchro.i_n_b,
 447                   p_vpar->p_vout->render_time,
 448                   p_vpar->synchro.i_not_chosen_pic,
 449                   p_vpar->synchro.i_trashed_pic -
 450                   p_vpar->synchro.i_not_chosen_pic,
 451                   p_vpar->synchro.i_pic );
 452             p_vpar->synchro.i_trashed_pic = p_vpar->synchro.i_not_chosen_pic
 453                 = p_vpar->synchro.i_pic = 0;
 454         }
 455 #endif
 456         break;
 457     case P_CODING_TYPE:
 458         p_vpar->synchro.i_eta_p++;
 459         if( p_vpar->synchro.i_eta_b
 460                 && p_vpar->synchro.i_eta_b != p_vpar->synchro.i_n_b )
 461         {
 462             intf_WarnMsg( 1, "Stream periodicity changed from B[%d] to B[%d]",
 463                           p_vpar->synchro.i_n_b, p_vpar->synchro.i_eta_b );
 464             p_vpar->synchro.i_n_b = p_vpar->synchro.i_eta_b;
 465         }
 466         p_vpar->synchro.i_eta_b = 0;
 467         break;
 468     case B_CODING_TYPE:
 469         p_vpar->synchro.i_eta_b++;
 470         break;
 471     }
 472
 473     /* FIXME: use decoder_fifo callback */
 474     p_pes = DECODER_FIFO_START( *p_vpar->bit_stream.p_decoder_fifo );
 475
 476     if( b_repeat_field )
 477     {
 478         /* MPEG-2 repeat_first_field */
 479         /* FIXME : this is not exactly what we should do, repeat_first_field
 480          * only regards the next picture */
 481         p_vpar->synchro.current_pts += period + (period >> 1);
 482     }
 483     else
 484     {
 485         p_vpar->synchro.current_pts += period;
 486     }
 487
 488     if( i_coding_type == B_CODING_TYPE )
 489     {
 490         if( p_pes->i_pts )
 491         {
 492             if( p_pes->i_pts - p_vpar->synchro.current_pts > PTS_THRESHOLD
 493                  || p_vpar->synchro.current_pts - p_pes->i_pts > PTS_THRESHOLD )
 494             {
 495                 intf_WarnMsg( 2,
 496                         "vpar synchro warning: pts != current_date (%lld)",
 497                         p_vpar->synchro.current_pts - p_pes->i_pts );
 498             }
 499             p_vpar->synchro.current_pts = p_pes->i_pts;
 500             p_pes->i_pts = 0;
 501         }
 502     }
 503     else
 504     {
 505         if( p_vpar->synchro.backward_pts )
 506         {
 507             if( p_pes->i_dts &&
 508                 (p_pes->i_dts - p_vpar->synchro.backward_pts > PTS_THRESHOLD
 509               || p_vpar->synchro.backward_pts - p_pes->i_dts > PTS_THRESHOLD) )
 510             {
 511                 intf_WarnMsg( 2,
 512                         "vpar synchro warning: backward_pts != dts (%lld)",
 513                         p_vpar->synchro.backward_pts - p_pes->i_dts );
 514             }
 515
 516             if( p_vpar->synchro.backward_pts - p_vpar->synchro.current_pts
 517                     > PTS_THRESHOLD
 518                  || p_vpar->synchro.current_pts - p_vpar->synchro.backward_pts
 519                     > PTS_THRESHOLD )
 520             {
 521                 intf_WarnMsg( 2,
 522                    "vpar synchro warning: backward_pts != current_pts (%lld)",
 523                    p_vpar->synchro.current_pts - p_vpar->synchro.backward_pts );
 524             }
 525             p_vpar->synchro.current_pts = p_vpar->synchro.backward_pts;
 526             p_vpar->synchro.backward_pts = 0;
 527         }
 528         else if( p_pes->i_dts )
 529         {
 530             if( p_pes->i_dts - p_vpar->synchro.current_pts > PTS_THRESHOLD
 531                  || p_vpar->synchro.current_pts - p_pes->i_dts > PTS_THRESHOLD )
 532             {
 533                 intf_WarnMsg( 2,
 534                         "vpar synchro warning: dts != current_pts (%lld)",
 535                         p_vpar->synchro.current_pts - p_pes->i_dts );
 536             }
 537             /* By definition of a DTS. */
 538             p_vpar->synchro.current_pts = p_pes->i_dts;
 539             p_pes->i_dts = 0;
 540         }
 541
 542         if( p_pes->i_pts )
 543         {
 544 #if 0
 545             int     i_n_b;
 546 #endif
 547
 548             /* Store the PTS for the next time we have to date an I picture. */
 549             p_vpar->synchro.backward_pts = p_pes->i_pts;
 550             p_pes->i_pts = 0;
 551             /* FIXME : disabled because it conflicts with streams having
 552              * b_repeat_first_field */
 553 #if 0
 554             i_n_b = (p_vpar->synchro.backward_pts
 555                         - p_vpar->synchro.current_pts) / period - 1;
 556             if( i_n_b != p_vpar->synchro.i_n_b )
 557             {
 558                 intf_WarnMsg( 1,
 559                         "Anticipating a stream periodicity change from"
 560                         " B[%d] to B[%d]",
 561                               p_vpar->synchro.i_n_b, i_n_b );
 562                 p_vpar->synchro.i_n_b = i_n_b;
 563             }
 564 #endif
 565         }
 566     }
 567
 568 #ifdef STATS
 569     p_vpar->synchro.i_pic++;
 570 #endif
 571 }
 572
 573 /*****************************************************************************
 574  * SynchroType: Get the user's synchro type
 575  *****************************************************************************
 576  * This function is called at initialization.
 577  *****************************************************************************/
 578 static int SynchroType( void )
 579 {
 580     char * psz_synchro = main_GetPszVariable( VPAR_SYNCHRO_VAR, NULL );
 581
 582     if( psz_synchro == NULL )
 583     {
 584         return VPAR_SYNCHRO_DEFAULT;
 585     }
 586
 587     switch( *psz_synchro++ )
 588     {
 589       case 'i':
 590       case 'I':
 591         switch( *psz_synchro++ )
 592         {
 593           case '\0':
 594             return VPAR_SYNCHRO_I;
 595
 596           case '+':
 597             if( *psz_synchro ) return 0;
 598             return VPAR_SYNCHRO_Iplus;
 599
 600           case 'p':
 601           case 'P':
 602             switch( *psz_synchro++ )
 603             {
 604               case '\0':
 605                 return VPAR_SYNCHRO_IP;
 606
 607               case '+':
 608                 if( *psz_synchro ) return 0;
 609                 return VPAR_SYNCHRO_IPplus;
 610
 611               case 'b':
 612               case 'B':
 613                 if( *psz_synchro ) return 0;
 614                 return VPAR_SYNCHRO_IPB;
 615
 616               default:
 617                 return VPAR_SYNCHRO_DEFAULT;
 618
 619             }
 620
 621           default:
 622             return VPAR_SYNCHRO_DEFAULT;
 623         }
 624     }
 625
 626     return VPAR_SYNCHRO_DEFAULT;
 627 }
 628