git.sesse.net Git - vlc/blob - modules/codec/mpeg_video/synchro.c

   1 /*****************************************************************************
   2  * vpar_synchro.c : frame dropping routines
   3  *****************************************************************************
   4  * Copyright (C) 1999-2001 VideoLAN
   5  * $Id: synchro.c,v 1.1 2002/08/04 17:23:42 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 <stdlib.h>                                                /* free() */
  98 #include <string.h>                                    /* memcpy(), memset() */
  99
 100 #include <vlc/vlc.h>
 101 #include <vlc/vout.h>
 102 #include <vlc/decoder.h>
 103
 104 #include "vdec_ext-plugins.h"
 105
 106 #include "decoder.h"
 107 #include "pool.h"
 108 #include "parser.h"
 109
 110 /*
 111  * Local prototypes
 112  */
 113 static int  SynchroType( decoder_fifo_t * );
 114
 115 /* Error margins */
 116 #define DELTA                   (int)(0.075*CLOCK_FREQ)
 117
 118 #define DEFAULT_NB_P            5
 119 #define DEFAULT_NB_B            1
 120
 121 /*****************************************************************************
 122  * vpar_SynchroInit : You know what ?
 123  *****************************************************************************/
 124 void vpar_SynchroInit( vpar_thread_t * p_vpar )
 125 {
 126     p_vpar->synchro.i_type = SynchroType( p_vpar->p_fifo );
 127
 128     /* We use a fake stream pattern, which is often right. */
 129     p_vpar->synchro.i_n_p = p_vpar->synchro.i_eta_p = DEFAULT_NB_P;
 130     p_vpar->synchro.i_n_b = p_vpar->synchro.i_eta_b = DEFAULT_NB_B;
 131     memset( p_vpar->synchro.p_tau, 0, 4 * sizeof(mtime_t) );
 132     memset( p_vpar->synchro.pi_meaningful, 0, 4 * sizeof(unsigned int) );
 133     p_vpar->synchro.b_dropped_last = 0;
 134     p_vpar->synchro.current_pts = mdate() + DEFAULT_PTS_DELAY;
 135     p_vpar->synchro.backward_pts = 0;
 136     p_vpar->synchro.i_current_period = p_vpar->synchro.i_backward_period = 0;
 137     p_vpar->synchro.i_trashed_pic = p_vpar->synchro.i_not_chosen_pic =
 138         p_vpar->synchro.i_pic = 0;
 139 }
 140
 141 /*****************************************************************************
 142  * vpar_SynchroChoose : Decide whether we will decode a picture or not
 143  *****************************************************************************/
 144 vlc_bool_t vpar_SynchroChoose( vpar_thread_t * p_vpar, int i_coding_type,
 145                                int i_structure )
 146 {
 147     /* For clarity reasons, we separated the special synchros code from the
 148      * mathematical synchro */
 149
 150     if( p_vpar->synchro.i_type != VPAR_SYNCHRO_DEFAULT )
 151     {
 152         switch( i_coding_type )
 153         {
 154         case I_CODING_TYPE:
 155             /* I, IP, IP+, IPB */
 156             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_Iplus )
 157             {
 158                 p_vpar->synchro.b_dropped_last = 1;
 159             }
 160             return( 1 );
 161
 162         case P_CODING_TYPE:
 163             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_I ) /* I */
 164             {
 165                 return( 0 );
 166             }
 167
 168             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_Iplus ) /* I+ */
 169             {
 170                 if( p_vpar->synchro.b_dropped_last )
 171                 {
 172                     p_vpar->synchro.b_dropped_last = 0;
 173                     return( 1 );
 174                 }
 175                 else
 176                 {
 177                     return( 0 );
 178                 }
 179             }
 180
 181             return( 1 ); /* IP, IP+, IPB */
 182
 183         case B_CODING_TYPE:
 184             if( p_vpar->synchro.i_type <= VPAR_SYNCHRO_IP ) /* I, IP */
 185             {
 186                 return( 0 );
 187             }
 188             else if( p_vpar->synchro.i_type == VPAR_SYNCHRO_IPB ) /* IPB */
 189             {
 190                 return( 1 );
 191             }
 192
 193             p_vpar->synchro.b_dropped_last ^= 1; /* IP+ */
 194             return( !p_vpar->synchro.b_dropped_last );
 195         }
 196         return( 0 ); /* never reached but gcc yells at me */
 197     }
 198     else
 199     {
 200 #define TAU_PRIME( coding_type )    (p_vpar->synchro.p_tau[(coding_type)] \
 201                                  + (p_vpar->synchro.p_tau[(coding_type)] >> 1) \
 202                                             + tau_yuv)
 203 #define S                           p_vpar->synchro
 204         /* VPAR_SYNCHRO_DEFAULT */
 205         mtime_t         now, period, tau_yuv;
 206         mtime_t         pts = 0;
 207         vlc_bool_t      b_decode = 0;
 208
 209         now = mdate();
 210         period = 1000000 * 1001 / p_vpar->sequence.i_frame_rate
 211                     * p_vpar->sequence.i_current_rate / DEFAULT_RATE;
 212
 213         vlc_mutex_lock( &p_vpar->p_vout->change_lock );
 214         tau_yuv = p_vpar->p_vout->render_time;
 215         vlc_mutex_unlock( &p_vpar->p_vout->change_lock );
 216
 217         switch( i_coding_type )
 218         {
 219         case I_CODING_TYPE:
 220             if( S.backward_pts )
 221             {
 222                 pts = S.backward_pts;
 223             }
 224             else
 225             {
 226                 /* displaying order : B B P B B I
 227                  *                      ^       ^
 228                  *                      |       +- current picture
 229                  *                      +- current PTS
 230                  */
 231                 pts = S.current_pts + period * (S.i_n_b + 2);
 232             }
 233
 234             if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
 235                     S.p_tau[I_CODING_TYPE] )
 236             {
 237                 b_decode = 1;
 238             }
 239             else
 240             {
 241                 b_decode = (pts - now) > (TAU_PRIME(I_CODING_TYPE) + DELTA);
 242             }
 243             if( !b_decode )
 244                 msg_Warn( p_vpar->p_fifo,
 245                           "synchro trashing I (%lld)", pts - now );
 246             break;
 247
 248         case P_CODING_TYPE:
 249             if( S.backward_pts )
 250             {
 251                 pts = S.backward_pts;
 252             }
 253             else
 254             {
 255                 pts = S.current_pts + period * (S.i_n_b + 1);
 256             }
 257
 258             if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
 259                     S.p_tau[I_CODING_TYPE] )
 260             {
 261                 if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
 262                 {
 263                     /* Security in case we're _really_ late */
 264                     b_decode = (pts - now > 0);
 265                 }
 266                 else
 267                 {
 268                     b_decode = (pts - now) > (TAU_PRIME(P_CODING_TYPE) + DELTA);
 269                     /* next I */
 270                     b_decode &= (pts - now
 271                                   + period
 272                               * ( (S.i_n_p - S.i_eta_p) * (1 + S.i_n_b) - 1 ))
 273                                 > (TAU_PRIME(P_CODING_TYPE)
 274                                     + TAU_PRIME(I_CODING_TYPE) + DELTA);
 275                 }
 276             }
 277             else
 278             {
 279                 b_decode = 0;
 280             }
 281             break;
 282
 283         case B_CODING_TYPE:
 284             pts = S.current_pts;
 285
 286             if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
 287             {
 288                 b_decode = (pts - now) > (TAU_PRIME(B_CODING_TYPE) + DELTA);
 289             }
 290             else
 291             {
 292                 b_decode = 0;
 293             }
 294         }
 295
 296         if( !b_decode )
 297         {
 298             S.i_not_chosen_pic++;
 299         }
 300         return( b_decode );
 301 #undef S
 302 #undef TAU_PRIME
 303     }
 304 }
 305
 306 /*****************************************************************************
 307  * vpar_SynchroTrash : Update counters when we trash a picture
 308  *****************************************************************************/
 309 void vpar_SynchroTrash( vpar_thread_t * p_vpar, int i_coding_type,
 310                         int i_structure )
 311 {
 312     p_vpar->synchro.i_trashed_pic++;
 313 }
 314
 315 /*****************************************************************************
 316  * vpar_SynchroDecode : Update timers when we decide to decode a picture
 317  *****************************************************************************/
 318 void vpar_SynchroDecode( vpar_thread_t * p_vpar, int i_coding_type,
 319                          int i_structure )
 320 {
 321     p_vpar->synchro.decoding_start = mdate();
 322 }
 323
 324 /*****************************************************************************
 325  * vpar_SynchroEnd : Called when the image is totally decoded
 326  *****************************************************************************/
 327 void vpar_SynchroEnd( vpar_thread_t * p_vpar, int i_coding_type,
 328                       int i_structure, int i_garbage )
 329 {
 330     mtime_t     tau;
 331
 332     if( !i_garbage )
 333     {
 334         tau = mdate() - p_vpar->synchro.decoding_start;
 335
 336         /* If duration too high, something happened (pause ?), so don't
 337          * take it into account. */
 338         if( tau < 3 * p_vpar->synchro.p_tau[i_coding_type]
 339              || !p_vpar->synchro.pi_meaningful[i_coding_type] )
 340         {
 341             /* Mean with average tau, to ensure stability. */
 342             p_vpar->synchro.p_tau[i_coding_type] =
 343                 (p_vpar->synchro.pi_meaningful[i_coding_type]
 344                  * p_vpar->synchro.p_tau[i_coding_type] + tau)
 345                 / (p_vpar->synchro.pi_meaningful[i_coding_type] + 1);
 346             if( p_vpar->synchro.pi_meaningful[i_coding_type] < MAX_PIC_AVERAGE )
 347             {
 348                 p_vpar->synchro.pi_meaningful[i_coding_type]++;
 349             }
 350         }
 351     }
 352 }
 353
 354 /*****************************************************************************
 355  * vpar_SynchroDate : When an image has been decoded, ask for its date
 356  *****************************************************************************/
 357 mtime_t vpar_SynchroDate( vpar_thread_t * p_vpar )
 358 {
 359     /* No need to lock, since PTS are only used by the video parser. */
 360     return( p_vpar->synchro.current_pts );
 361 }
 362
 363 /*****************************************************************************
 364  * vpar_SynchroNewPicture: Update stream structure and PTS
 365  *****************************************************************************/
 366 void vpar_SynchroNewPicture( vpar_thread_t * p_vpar, int i_coding_type,
 367                              int i_repeat_field )
 368 {
 369     mtime_t         period = 1000000 * 1001 / p_vpar->sequence.i_frame_rate
 370                               * p_vpar->sequence.i_current_rate / DEFAULT_RATE;
 371 #if 0
 372     mtime_t         now = mdate();
 373 #endif
 374
 375     switch( i_coding_type )
 376     {
 377     case I_CODING_TYPE:
 378         if( p_vpar->synchro.i_eta_p
 379              && p_vpar->synchro.i_eta_p != p_vpar->synchro.i_n_p )
 380         {
 381             msg_Warn( p_vpar->p_fifo,
 382                       "stream periodicity changed from P[%d] to P[%d]",
 383                       p_vpar->synchro.i_n_p, p_vpar->synchro.i_eta_p );
 384             p_vpar->synchro.i_n_p = p_vpar->synchro.i_eta_p;
 385         }
 386         p_vpar->synchro.i_eta_p = p_vpar->synchro.i_eta_b = 0;
 387
 388         if( p_vpar->synchro.i_type == VPAR_SYNCHRO_DEFAULT )
 389         {
 390             msg_Dbg( p_vpar->p_fifo, "I(%lld) P(%lld)[%d] B(%lld)[%d] YUV(%lld) : trashed %d:%d/%d",
 391                   p_vpar->synchro.p_tau[I_CODING_TYPE],
 392                   p_vpar->synchro.p_tau[P_CODING_TYPE],
 393                   p_vpar->synchro.i_n_p,
 394                   p_vpar->synchro.p_tau[B_CODING_TYPE],
 395                   p_vpar->synchro.i_n_b,
 396                   p_vpar->p_vout->render_time,
 397                   p_vpar->synchro.i_not_chosen_pic,
 398                   p_vpar->synchro.i_trashed_pic -
 399                   p_vpar->synchro.i_not_chosen_pic,
 400                   p_vpar->synchro.i_pic );
 401             p_vpar->synchro.i_trashed_pic = p_vpar->synchro.i_not_chosen_pic
 402                 = p_vpar->synchro.i_pic = 0;
 403         }
 404         break;
 405
 406     case P_CODING_TYPE:
 407         p_vpar->synchro.i_eta_p++;
 408         if( p_vpar->synchro.i_eta_b
 409              && p_vpar->synchro.i_eta_b != p_vpar->synchro.i_n_b )
 410         {
 411             msg_Warn( p_vpar->p_fifo,
 412                       "stream periodicity changed from B[%d] to B[%d]",
 413                       p_vpar->synchro.i_n_b, p_vpar->synchro.i_eta_b );
 414             p_vpar->synchro.i_n_b = p_vpar->synchro.i_eta_b;
 415         }
 416         p_vpar->synchro.i_eta_b = 0;
 417         break;
 418     case B_CODING_TYPE:
 419         p_vpar->synchro.i_eta_b++;
 420         break;
 421     }
 422
 423     p_vpar->synchro.current_pts += p_vpar->synchro.i_current_period
 424                                         * (period >> 1);
 425
 426 #define PTS_THRESHOLD   (period >> 2)
 427     if( i_coding_type == B_CODING_TYPE )
 428     {
 429         /* A video frame can be displayed 1, 2 or 3 times, according to
 430          * repeat_first_field, top_field_first, progressive_sequence and
 431          * progressive_frame. */
 432         p_vpar->synchro.i_current_period = i_repeat_field;
 433
 434         if( p_vpar->sequence.next_pts )
 435         {
 436             if( p_vpar->sequence.next_pts - p_vpar->synchro.current_pts
 437                     > PTS_THRESHOLD
 438                  || p_vpar->synchro.current_pts - p_vpar->sequence.next_pts
 439                     > PTS_THRESHOLD )
 440             {
 441                 msg_Warn( p_vpar->p_fifo,
 442                           "vpar synchro warning: pts != current_date (%lld)",
 443                           p_vpar->synchro.current_pts
 444                               - p_vpar->sequence.next_pts );
 445             }
 446             p_vpar->synchro.current_pts = p_vpar->sequence.next_pts;
 447             p_vpar->sequence.next_pts = 0;
 448         }
 449     }
 450     else
 451     {
 452         p_vpar->synchro.i_current_period = p_vpar->synchro.i_backward_period;
 453         p_vpar->synchro.i_backward_period = i_repeat_field;
 454
 455         if( p_vpar->synchro.backward_pts )
 456         {
 457             if( p_vpar->sequence.next_dts &&
 458                 (p_vpar->sequence.next_dts - p_vpar->synchro.backward_pts
 459                     > PTS_THRESHOLD
 460               || p_vpar->synchro.backward_pts - p_vpar->sequence.next_dts
 461                     > PTS_THRESHOLD) )
 462             {
 463                 msg_Warn( p_vpar->p_fifo, "backward_pts != dts (%lld)",
 464                            p_vpar->sequence.next_dts
 465                                - p_vpar->synchro.backward_pts );
 466             }
 467             if( p_vpar->synchro.backward_pts - p_vpar->synchro.current_pts
 468                     > PTS_THRESHOLD
 469                  || p_vpar->synchro.current_pts - p_vpar->synchro.backward_pts
 470                     > PTS_THRESHOLD )
 471             {
 472                 msg_Warn( p_vpar->p_fifo,
 473                           "backward_pts != current_pts (%lld)",
 474                           p_vpar->synchro.current_pts
 475                               - p_vpar->synchro.backward_pts );
 476             }
 477             p_vpar->synchro.current_pts = p_vpar->synchro.backward_pts;
 478             p_vpar->synchro.backward_pts = 0;
 479         }
 480         else if( p_vpar->sequence.next_dts )
 481         {
 482             if( p_vpar->sequence.next_dts - p_vpar->synchro.current_pts
 483                     > PTS_THRESHOLD
 484                  || p_vpar->synchro.current_pts - p_vpar->sequence.next_dts
 485                     > PTS_THRESHOLD )
 486             {
 487                 msg_Warn( p_vpar->p_fifo, "dts != current_pts (%lld)",
 488                           p_vpar->synchro.current_pts
 489                               - p_vpar->sequence.next_dts );
 490             }
 491             /* By definition of a DTS. */
 492             p_vpar->synchro.current_pts = p_vpar->sequence.next_dts;
 493             p_vpar->sequence.next_dts = 0;
 494         }
 495
 496         if( p_vpar->sequence.next_pts )
 497         {
 498             /* Store the PTS for the next time we have to date an I picture. */
 499             p_vpar->synchro.backward_pts = p_vpar->sequence.next_pts;
 500             p_vpar->sequence.next_pts = 0;
 501         }
 502     }
 503 #undef PTS_THRESHOLD
 504
 505 #if 0
 506     /* Removed for incompatibility with slow motion */
 507     if( p_vpar->synchro.current_pts + DEFAULT_PTS_DELAY < now )
 508     {
 509         /* We cannot be _that_ late, something must have happened, reinit
 510          * the dates. */
 511         msg_Warn( p_vpar->p_fifo, "PTS << now (%lld), resetting",
 512                    now - p_vpar->synchro.current_pts - DEFAULT_PTS_DELAY );
 513         p_vpar->synchro.current_pts = now + DEFAULT_PTS_DELAY;
 514     }
 515     if( p_vpar->synchro.backward_pts
 516          && p_vpar->synchro.backward_pts + DEFAULT_PTS_DELAY < now )
 517     {
 518         /* The same. */
 519         p_vpar->synchro.backward_pts = 0;
 520     }
 521 #endif
 522
 523     p_vpar->synchro.i_pic++;
 524 }
 525
 526 /*****************************************************************************
 527  * SynchroType: Get the user's synchro type
 528  *****************************************************************************
 529  * This function is called at initialization.
 530  *****************************************************************************/
 531 static int SynchroType( decoder_fifo_t *p_this )
 532 {
 533     char psz_synchro_tmp[5];
 534     char * psz_synchro = config_GetPsz( p_this, "vpar-synchro" );
 535
 536     if( psz_synchro == NULL )
 537     {
 538         return VPAR_SYNCHRO_DEFAULT;
 539     }
 540
 541     strncpy( psz_synchro_tmp, psz_synchro, 5);
 542     free( psz_synchro );
 543     psz_synchro = psz_synchro_tmp;
 544
 545     switch( *psz_synchro++ )
 546     {
 547       case 'i':
 548       case 'I':
 549         switch( *psz_synchro++ )
 550         {
 551           case '\0':
 552             return VPAR_SYNCHRO_I;
 553
 554           case '+':
 555             if( *psz_synchro ) return 0;
 556             return VPAR_SYNCHRO_Iplus;
 557
 558           case 'p':
 559           case 'P':
 560             switch( *psz_synchro++ )
 561             {
 562               case '\0':
 563                 return VPAR_SYNCHRO_IP;
 564
 565               case '+':
 566                 if( *psz_synchro ) return 0;
 567                 return VPAR_SYNCHRO_IPplus;
 568
 569               case 'b':
 570               case 'B':
 571                 if( *psz_synchro ) return 0;
 572                 return VPAR_SYNCHRO_IPB;
 573
 574               default:
 575                 return VPAR_SYNCHRO_DEFAULT;
 576
 577             }
 578
 579           default:
 580             return VPAR_SYNCHRO_DEFAULT;
 581         }
 582     }
 583
 584     return VPAR_SYNCHRO_DEFAULT;
 585 }
 586