git.sesse.net Git - vlc/blob - src/video_output/vout_synchro.c

   1 /*****************************************************************************
   2  * vout_synchro.c : frame dropping routines
   3  *****************************************************************************
   4  * Copyright (C) 1999-2005 the VideoLAN team
   5  * $Id$
   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., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, 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_input.h>
 103 #include <vlc_vout_synchro.h>
 104
 105 /*
 106  * Local prototypes
 107  */
 108
 109 /* Error margins */
 110 #define DELTA                   (int)(0.075*CLOCK_FREQ)
 111 #define MAX_VALID_TAU           (int)(0.3*CLOCK_FREQ)
 112
 113 #define DEFAULT_NB_P            5
 114 #define DEFAULT_NB_B            1
 115
 116 /*****************************************************************************
 117  * vout_SynchroInit : You know what ?
 118  *****************************************************************************/
 119 vout_synchro_t * __vout_SynchroInit( vlc_object_t * p_object,
 120                                      int i_frame_rate )
 121 {
 122     vout_synchro_t * p_synchro = vlc_object_create( p_object,
 123                                                   sizeof(vout_synchro_t) );
 124     if ( p_synchro == NULL )
 125     {
 126         msg_Err( p_object, "out of memory" );
 127         return NULL;
 128     }
 129     vlc_object_attach( p_synchro, p_object );
 130
 131     p_synchro->b_no_skip = !config_GetInt( p_object, "skip-frames" );
 132     p_synchro->b_quiet = config_GetInt( p_object, "quiet-synchro" );
 133
 134     /* We use a fake stream pattern, which is often right. */
 135     p_synchro->i_n_p = p_synchro->i_eta_p = DEFAULT_NB_P;
 136     p_synchro->i_n_b = p_synchro->i_eta_b = DEFAULT_NB_B;
 137     memset( p_synchro->p_tau, 0, 4 * sizeof(mtime_t) );
 138     memset( p_synchro->pi_meaningful, 0, 4 * sizeof(unsigned int) );
 139     p_synchro->i_nb_ref = 0;
 140     p_synchro->i_trash_nb_ref = p_synchro->i_dec_nb_ref = 0;
 141     p_synchro->current_pts = mdate() + DEFAULT_PTS_DELAY;
 142     p_synchro->backward_pts = 0;
 143     p_synchro->i_current_period = p_synchro->i_backward_period = 0;
 144     p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic =
 145         p_synchro->i_pic = 0;
 146
 147     p_synchro->i_frame_rate = i_frame_rate;
 148
 149     return p_synchro;
 150 }
 151
 152 /*****************************************************************************
 153  * vout_SynchroRelease : You know what ?
 154  *****************************************************************************/
 155 void vout_SynchroRelease( vout_synchro_t * p_synchro )
 156 {
 157     vlc_object_detach( p_synchro );
 158     vlc_object_destroy( p_synchro );
 159 }
 160
 161 /*****************************************************************************
 162  * vout_SynchroReset : Reset the reference picture counter
 163  *****************************************************************************/
 164 void vout_SynchroReset( vout_synchro_t * p_synchro )
 165 {
 166     p_synchro->i_nb_ref = 0;
 167     p_synchro->i_trash_nb_ref = p_synchro->i_dec_nb_ref = 0;
 168 }
 169
 170 /*****************************************************************************
 171  * vout_SynchroChoose : Decide whether we will decode a picture or not
 172  *****************************************************************************/
 173 vlc_bool_t vout_SynchroChoose( vout_synchro_t * p_synchro, int i_coding_type,
 174                                int i_render_time, vlc_bool_t b_low_delay )
 175 {
 176 #define TAU_PRIME( coding_type )    (p_synchro->p_tau[(coding_type)] \
 177                                     + (p_synchro->p_tau[(coding_type)] >> 1) \
 178                                     + p_synchro->i_render_time)
 179 #define S (*p_synchro)
 180     mtime_t         now, period;
 181     mtime_t         pts = 0;
 182     vlc_bool_t      b_decode = 0;
 183
 184     if ( p_synchro->b_no_skip )
 185         return 1;
 186
 187     now = mdate();
 188     period = 1000000 * 1001 / p_synchro->i_frame_rate
 189                      * p_synchro->i_current_rate / INPUT_RATE_DEFAULT;
 190
 191     p_synchro->i_render_time = i_render_time;
 192
 193     switch( i_coding_type )
 194     {
 195     case I_CODING_TYPE:
 196         if( b_low_delay )
 197         {
 198             pts = S.current_pts;
 199         }
 200         else if( S.backward_pts )
 201         {
 202             pts = S.backward_pts;
 203         }
 204         else
 205         {
 206             /* displaying order : B B P B B I
 207              *                      ^       ^
 208              *                      |       +- current picture
 209              *                      +- current PTS
 210              */
 211             pts = S.current_pts + period * (S.i_n_b + 2);
 212         }
 213
 214         if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
 215                 S.p_tau[I_CODING_TYPE] )
 216         {
 217             b_decode = 1;
 218         }
 219         else
 220         {
 221             b_decode = (pts - now) > (TAU_PRIME(I_CODING_TYPE) + DELTA);
 222         }
 223         if( !b_decode && !p_synchro->b_quiet )
 224         {
 225             msg_Warn( p_synchro,
 226                       "synchro trashing I ("I64Fd")", pts - now );
 227         }
 228         break;
 229
 230     case P_CODING_TYPE:
 231         if( b_low_delay )
 232         {
 233             pts = S.current_pts;
 234         }
 235         else if( S.backward_pts )
 236         {
 237             pts = S.backward_pts;
 238         }
 239         else
 240         {
 241             pts = S.current_pts + period * (S.i_n_b + 1);
 242         }
 243
 244         if( p_synchro->i_nb_ref < 1 )
 245         {
 246             b_decode = 0;
 247         }
 248         else if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
 249                 S.p_tau[I_CODING_TYPE] )
 250         {
 251             if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
 252             {
 253                 /* Security in case we're _really_ late */
 254                 b_decode = (pts - now > 0);
 255             }
 256             else
 257             {
 258                 b_decode = (pts - now) > (TAU_PRIME(P_CODING_TYPE) + DELTA);
 259                 /* next I */
 260                 b_decode &= (pts - now
 261                               + period
 262                           * ( (S.i_n_p - S.i_eta_p) * (1 + S.i_n_b) - 1 ))
 263                             > (TAU_PRIME(P_CODING_TYPE)
 264                                 + TAU_PRIME(I_CODING_TYPE) + DELTA);
 265             }
 266         }
 267         else
 268         {
 269             b_decode = 0;
 270         }
 271         break;
 272
 273     case B_CODING_TYPE:
 274         pts = S.current_pts;
 275
 276         if( p_synchro->i_nb_ref < 2 )
 277         {
 278             b_decode = 0;
 279         }
 280         else if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
 281         {
 282             b_decode = (pts - now) > (TAU_PRIME(B_CODING_TYPE) + DELTA);
 283         }
 284         else
 285         {
 286             b_decode = 0;
 287         }
 288     }
 289
 290     if( !b_decode )
 291     {
 292         S.i_not_chosen_pic++;
 293     }
 294     return( b_decode );
 295 #undef S
 296 #undef TAU_PRIME
 297 }
 298
 299 /*****************************************************************************
 300  * vout_SynchroTrash : Update counters when we trash a picture
 301  *****************************************************************************/
 302 void vout_SynchroTrash( vout_synchro_t * p_synchro )
 303 {
 304     p_synchro->i_trashed_pic++;
 305     p_synchro->i_nb_ref = p_synchro->i_trash_nb_ref;
 306 }
 307
 308 /*****************************************************************************
 309  * vout_SynchroDecode : Update timers when we decide to decode a picture
 310  *****************************************************************************/
 311 void vout_SynchroDecode( vout_synchro_t * p_synchro )
 312 {
 313     p_synchro->decoding_start = mdate();
 314     p_synchro->i_nb_ref = p_synchro->i_dec_nb_ref;
 315 }
 316
 317 /*****************************************************************************
 318  * vout_SynchroEnd : Called when the image is totally decoded
 319  *****************************************************************************/
 320 void vout_SynchroEnd( vout_synchro_t * p_synchro, int i_coding_type,
 321                       vlc_bool_t b_garbage )
 322 {
 323     mtime_t     tau;
 324
 325     if( !b_garbage )
 326     {
 327         tau = mdate() - p_synchro->decoding_start;
 328
 329         /* If duration too high, something happened (pause ?), so don't
 330          * take it into account. */
 331         if( tau < 3 * p_synchro->p_tau[i_coding_type]
 332              || ( !p_synchro->pi_meaningful[i_coding_type]
 333                    && tau < MAX_VALID_TAU ) )
 334         {
 335             /* Mean with average tau, to ensure stability. */
 336             p_synchro->p_tau[i_coding_type] =
 337                 (p_synchro->pi_meaningful[i_coding_type]
 338                  * p_synchro->p_tau[i_coding_type] + tau)
 339                 / (p_synchro->pi_meaningful[i_coding_type] + 1);
 340             if( p_synchro->pi_meaningful[i_coding_type] < MAX_PIC_AVERAGE )
 341             {
 342                 p_synchro->pi_meaningful[i_coding_type]++;
 343             }
 344         }
 345     }
 346 }
 347
 348 /*****************************************************************************
 349  * vout_SynchroDate : When an image has been decoded, ask for its date
 350  *****************************************************************************/
 351 mtime_t vout_SynchroDate( vout_synchro_t * p_synchro )
 352 {
 353     /* No need to lock, since PTS are only used by the video parser. */
 354     return p_synchro->current_pts;
 355 }
 356
 357 /*****************************************************************************
 358  * vout_SynchroNewPicture: Update stream structure and PTS
 359  *****************************************************************************/
 360 void vout_SynchroNewPicture( vout_synchro_t * p_synchro, int i_coding_type,
 361                              int i_repeat_field, mtime_t next_pts,
 362                              mtime_t next_dts, int i_current_rate,
 363                              vlc_bool_t b_low_delay )
 364 {
 365     mtime_t         period = 1000000 * 1001 / p_synchro->i_frame_rate
 366                               * i_current_rate / INPUT_RATE_DEFAULT;
 367 #if 0
 368     mtime_t         now = mdate();
 369 #endif
 370     p_synchro->i_current_rate = i_current_rate;
 371
 372     switch( i_coding_type )
 373     {
 374     case I_CODING_TYPE:
 375         if( p_synchro->i_eta_p
 376              && p_synchro->i_eta_p != p_synchro->i_n_p )
 377         {
 378 #if 0
 379             if( !p_synchro->b_quiet )
 380                 msg_Dbg( p_synchro,
 381                          "stream periodicity changed from P[%d] to P[%d]",
 382                          p_synchro->i_n_p, p_synchro->i_eta_p );
 383 #endif
 384             p_synchro->i_n_p = p_synchro->i_eta_p;
 385         }
 386         p_synchro->i_eta_p = p_synchro->i_eta_b = 0;
 387         p_synchro->i_trash_nb_ref = 0;
 388         if( p_synchro->i_nb_ref < 2 )
 389             p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref + 1;
 390         else
 391             p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref;
 392
 393 #if 0
 394         if( !p_synchro->b_quiet )
 395             msg_Dbg( p_synchro, "I("I64Fd") P("I64Fd")[%d] B("I64Fd")"
 396                   "[%d] YUV("I64Fd") : trashed %d:%d/%d",
 397                   p_synchro->p_tau[I_CODING_TYPE],
 398                   p_synchro->p_tau[P_CODING_TYPE],
 399                   p_synchro->i_n_p,
 400                   p_synchro->p_tau[B_CODING_TYPE],
 401                   p_synchro->i_n_b,
 402                   p_synchro->i_render_time,
 403                   p_synchro->i_not_chosen_pic,
 404                   p_synchro->i_trashed_pic -
 405                   p_synchro->i_not_chosen_pic,
 406                   p_synchro->i_pic );
 407         p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
 408             = p_synchro->i_pic = 0;
 409 #else
 410         if( p_synchro->i_pic >= 100 )
 411         {
 412             if( !p_synchro->b_quiet && p_synchro->i_trashed_pic != 0 )
 413                 msg_Dbg( p_synchro, "decoded %d/%d pictures",
 414                          p_synchro->i_pic
 415                            - p_synchro->i_trashed_pic,
 416                          p_synchro->i_pic );
 417             p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
 418                 = p_synchro->i_pic = 0;
 419         }
 420 #endif
 421         break;
 422
 423     case P_CODING_TYPE:
 424         p_synchro->i_eta_p++;
 425         if( p_synchro->i_eta_b
 426              && p_synchro->i_eta_b != p_synchro->i_n_b )
 427         {
 428 #if 0
 429             if( !p_synchro->b_quiet )
 430                 msg_Dbg( p_synchro,
 431                          "stream periodicity changed from B[%d] to B[%d]",
 432                          p_synchro->i_n_b, p_synchro->i_eta_b );
 433 #endif
 434             p_synchro->i_n_b = p_synchro->i_eta_b;
 435         }
 436         p_synchro->i_eta_b = 0;
 437         p_synchro->i_dec_nb_ref = 2;
 438         p_synchro->i_trash_nb_ref = 0;
 439         break;
 440
 441     case B_CODING_TYPE:
 442         p_synchro->i_eta_b++;
 443         p_synchro->i_dec_nb_ref = p_synchro->i_trash_nb_ref
 444             = p_synchro->i_nb_ref;
 445         break;
 446     }
 447
 448     p_synchro->current_pts += p_synchro->i_current_period
 449                                         * (period >> 1);
 450
 451 #define PTS_THRESHOLD   (period >> 2)
 452     if( i_coding_type == B_CODING_TYPE || b_low_delay )
 453     {
 454         /* A video frame can be displayed 1, 2 or 3 times, according to
 455          * repeat_first_field, top_field_first, progressive_sequence and
 456          * progressive_frame. */
 457         p_synchro->i_current_period = i_repeat_field;
 458
 459         if( next_pts )
 460         {
 461             if( (next_pts - p_synchro->current_pts
 462                     > PTS_THRESHOLD
 463                   || p_synchro->current_pts - next_pts
 464                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
 465             {
 466                 msg_Warn( p_synchro, "vout synchro warning: pts != "
 467                           "current_date ("I64Fd")",
 468                           p_synchro->current_pts
 469                               - next_pts );
 470             }
 471             p_synchro->current_pts = next_pts;
 472         }
 473     }
 474     else
 475     {
 476         p_synchro->i_current_period = p_synchro->i_backward_period;
 477         p_synchro->i_backward_period = i_repeat_field;
 478
 479         if( p_synchro->backward_pts )
 480         {
 481             if( next_dts &&
 482                 (next_dts - p_synchro->backward_pts
 483                     > PTS_THRESHOLD
 484                   || p_synchro->backward_pts - next_dts
 485                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
 486             {
 487                 msg_Warn( p_synchro, "backward_pts != dts ("I64Fd")",
 488                            next_dts
 489                                - p_synchro->backward_pts );
 490             }
 491             if( (p_synchro->backward_pts - p_synchro->current_pts
 492                     > PTS_THRESHOLD
 493                   || p_synchro->current_pts - p_synchro->backward_pts
 494                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
 495             {
 496                 msg_Warn( p_synchro,
 497                           "backward_pts != current_pts ("I64Fd")",
 498                           p_synchro->current_pts
 499                               - p_synchro->backward_pts );
 500             }
 501             p_synchro->current_pts = p_synchro->backward_pts;
 502             p_synchro->backward_pts = 0;
 503         }
 504         else if( next_dts )
 505         {
 506             if( (next_dts - p_synchro->current_pts
 507                     > PTS_THRESHOLD
 508                   || p_synchro->current_pts - next_dts
 509                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
 510             {
 511                 msg_Warn( p_synchro, "dts != current_pts ("I64Fd")",
 512                           p_synchro->current_pts
 513                               - next_dts );
 514             }
 515             /* By definition of a DTS. */
 516             p_synchro->current_pts = next_dts;
 517             next_dts = 0;
 518         }
 519
 520         if( next_pts )
 521         {
 522             /* Store the PTS for the next time we have to date an I picture. */
 523             p_synchro->backward_pts = next_pts;
 524             next_pts = 0;
 525         }
 526     }
 527 #undef PTS_THRESHOLD
 528
 529 #if 0
 530     /* Removed for incompatibility with slow motion */
 531     if( p_synchro->current_pts + DEFAULT_PTS_DELAY < now )
 532     {
 533         /* We cannot be _that_ late, something must have happened, reinit
 534          * the dates. */
 535         if( !p_synchro->b_quiet )
 536             msg_Warn( p_synchro, "PTS << now ("I64Fd"), resetting",
 537                       now - p_synchro->current_pts - DEFAULT_PTS_DELAY );
 538         p_synchro->current_pts = now + DEFAULT_PTS_DELAY;
 539     }
 540     if( p_synchro->backward_pts
 541          && p_synchro->backward_pts + DEFAULT_PTS_DELAY < now )
 542     {
 543         /* The same. */
 544         p_synchro->backward_pts = 0;
 545     }
 546 #endif
 547
 548     p_synchro->i_pic++;
 549 }