git.sesse.net Git - vlc/blob - src/input/decoder_synchro.c

   1 /*****************************************************************************
   2  * decoder_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 <vlc/vlc.h>
  98 #include <vlc_input.h>
  99 #include <vlc_codec_synchro.h>
 100
 101 /*
 102  * Local prototypes
 103  */
 104
 105 #define MAX_PIC_AVERAGE         8
 106
 107 struct decoder_synchro_t
 108 {
 109     VLC_COMMON_MEMBERS
 110
 111     int             i_frame_rate;
 112     int             i_current_rate;
 113     vlc_bool_t      b_no_skip;
 114     vlc_bool_t      b_quiet;
 115
 116     /* date of the beginning of the decoding of the current picture */
 117     mtime_t         decoding_start;
 118
 119     /* stream properties */
 120     unsigned int    i_n_p, i_n_b;
 121
 122     /* decoding values */
 123     mtime_t         p_tau[4];                  /* average decoding durations */
 124     unsigned int    pi_meaningful[4];            /* number of durations read */
 125
 126     /* render_time filled by SynchroChoose() */
 127     int i_render_time;
 128
 129     /* stream context */
 130     int             i_nb_ref;                /* Number of reference pictures */
 131     int             i_dec_nb_ref;      /* Number of reference pictures we'll *
 132                                         * have if we decode the current pic  */
 133     int             i_trash_nb_ref;    /* Number of reference pictures we'll *
 134                                         * have if we trash the current pic   */
 135     unsigned int    i_eta_p, i_eta_b;
 136     mtime_t         backward_pts, current_pts;
 137     int             i_current_period;   /* period to add to the next picture */
 138     int             i_backward_period;  /* period to add after the next
 139                                          * reference picture
 140                                          * (backward_period * period / 2) */
 141
 142     /* statistics */
 143     unsigned int    i_trashed_pic, i_not_chosen_pic, i_pic;
 144 };
 145
 146 /* Error margins */
 147 #define DELTA                   (int)(0.075*CLOCK_FREQ)
 148 #define MAX_VALID_TAU           (int)(0.3*CLOCK_FREQ)
 149
 150 #define DEFAULT_NB_P            5
 151 #define DEFAULT_NB_B            1
 152
 153 /*****************************************************************************
 154  * decoder_SynchroInit : You know what ?
 155  *****************************************************************************/
 156 decoder_synchro_t * decoder_SynchroInit( decoder_t *p_dec,
 157                                      int i_frame_rate )
 158 {
 159     decoder_synchro_t * p_synchro = vlc_object_create( p_dec,
 160                                                   sizeof(decoder_synchro_t) );
 161     if ( p_synchro == NULL )
 162     {
 163         msg_Err( p_dec, "out of memory" );
 164         return NULL;
 165     }
 166     vlc_object_attach( p_synchro, p_dec );
 167
 168     p_synchro->b_no_skip = !config_GetInt( p_dec, "skip-frames" );
 169     p_synchro->b_quiet = config_GetInt( p_dec, "quiet-synchro" );
 170
 171     /* We use a fake stream pattern, which is often right. */
 172     p_synchro->i_n_p = p_synchro->i_eta_p = DEFAULT_NB_P;
 173     p_synchro->i_n_b = p_synchro->i_eta_b = DEFAULT_NB_B;
 174     memset( p_synchro->p_tau, 0, 4 * sizeof(mtime_t) );
 175     memset( p_synchro->pi_meaningful, 0, 4 * sizeof(unsigned int) );
 176     p_synchro->i_nb_ref = 0;
 177     p_synchro->i_trash_nb_ref = p_synchro->i_dec_nb_ref = 0;
 178     p_synchro->current_pts = mdate() + DEFAULT_PTS_DELAY;
 179     p_synchro->backward_pts = 0;
 180     p_synchro->i_current_period = p_synchro->i_backward_period = 0;
 181     p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic =
 182         p_synchro->i_pic = 0;
 183
 184     p_synchro->i_frame_rate = i_frame_rate;
 185
 186     return p_synchro;
 187 }
 188
 189 /*****************************************************************************
 190  * decoder_SynchroRelease : You know what ?
 191  *****************************************************************************/
 192 void decoder_SynchroRelease( decoder_synchro_t * p_synchro )
 193 {
 194     vlc_object_detach( p_synchro );
 195     vlc_object_destroy( p_synchro );
 196 }
 197
 198 /*****************************************************************************
 199  * decoder_SynchroReset : Reset the reference picture counter
 200  *****************************************************************************/
 201 void decoder_SynchroReset( decoder_synchro_t * p_synchro )
 202 {
 203     p_synchro->i_nb_ref = 0;
 204     p_synchro->i_trash_nb_ref = p_synchro->i_dec_nb_ref = 0;
 205 }
 206
 207 /*****************************************************************************
 208  * decoder_SynchroChoose : Decide whether we will decode a picture or not
 209  *****************************************************************************/
 210 vlc_bool_t decoder_SynchroChoose( decoder_synchro_t * p_synchro, int i_coding_type,
 211                                int i_render_time, vlc_bool_t b_low_delay )
 212 {
 213 #define TAU_PRIME( coding_type )    (p_synchro->p_tau[(coding_type)] \
 214                                     + (p_synchro->p_tau[(coding_type)] >> 1) \
 215                                     + p_synchro->i_render_time)
 216 #define S (*p_synchro)
 217     mtime_t         now, period;
 218     mtime_t         pts = 0;
 219     vlc_bool_t      b_decode = 0;
 220
 221     if ( p_synchro->b_no_skip )
 222         return 1;
 223
 224     now = mdate();
 225     period = 1000000 * 1001 / p_synchro->i_frame_rate
 226                      * p_synchro->i_current_rate / INPUT_RATE_DEFAULT;
 227
 228     p_synchro->i_render_time = i_render_time;
 229
 230     switch( i_coding_type )
 231     {
 232     case I_CODING_TYPE:
 233         if( b_low_delay )
 234         {
 235             pts = S.current_pts;
 236         }
 237         else if( S.backward_pts )
 238         {
 239             pts = S.backward_pts;
 240         }
 241         else
 242         {
 243             /* displaying order : B B P B B I
 244              *                      ^       ^
 245              *                      |       +- current picture
 246              *                      +- current PTS
 247              */
 248             pts = S.current_pts + period * (S.i_n_b + 2);
 249         }
 250
 251         if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
 252                 S.p_tau[I_CODING_TYPE] )
 253         {
 254             b_decode = 1;
 255         }
 256         else
 257         {
 258             b_decode = (pts - now) > (TAU_PRIME(I_CODING_TYPE) + DELTA);
 259         }
 260         if( !b_decode && !p_synchro->b_quiet )
 261         {
 262             msg_Warn( p_synchro,
 263                       "synchro trashing I ("I64Fd")", pts - now );
 264         }
 265         break;
 266
 267     case P_CODING_TYPE:
 268         if( b_low_delay )
 269         {
 270             pts = S.current_pts;
 271         }
 272         else if( S.backward_pts )
 273         {
 274             pts = S.backward_pts;
 275         }
 276         else
 277         {
 278             pts = S.current_pts + period * (S.i_n_b + 1);
 279         }
 280
 281         if( p_synchro->i_nb_ref < 1 )
 282         {
 283             b_decode = 0;
 284         }
 285         else if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
 286                 S.p_tau[I_CODING_TYPE] )
 287         {
 288             if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
 289             {
 290                 /* Security in case we're _really_ late */
 291                 b_decode = (pts - now > 0);
 292             }
 293             else
 294             {
 295                 b_decode = (pts - now) > (TAU_PRIME(P_CODING_TYPE) + DELTA);
 296                 /* next I */
 297                 b_decode &= (pts - now
 298                               + period
 299                           * ( (S.i_n_p - S.i_eta_p) * (1 + S.i_n_b) - 1 ))
 300                             > (TAU_PRIME(P_CODING_TYPE)
 301                                 + TAU_PRIME(I_CODING_TYPE) + DELTA);
 302             }
 303         }
 304         else
 305         {
 306             b_decode = 0;
 307         }
 308         break;
 309
 310     case B_CODING_TYPE:
 311         pts = S.current_pts;
 312
 313         if( p_synchro->i_nb_ref < 2 )
 314         {
 315             b_decode = 0;
 316         }
 317         else if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
 318         {
 319             b_decode = (pts - now) > (TAU_PRIME(B_CODING_TYPE) + DELTA);
 320         }
 321         else
 322         {
 323             b_decode = 0;
 324         }
 325     }
 326
 327     if( !b_decode )
 328     {
 329         S.i_not_chosen_pic++;
 330     }
 331     return( b_decode );
 332 #undef S
 333 #undef TAU_PRIME
 334 }
 335
 336 /*****************************************************************************
 337  * decoder_SynchroTrash : Update counters when we trash a picture
 338  *****************************************************************************/
 339 void decoder_SynchroTrash( decoder_synchro_t * p_synchro )
 340 {
 341     p_synchro->i_trashed_pic++;
 342     p_synchro->i_nb_ref = p_synchro->i_trash_nb_ref;
 343 }
 344
 345 /*****************************************************************************
 346  * decoder_SynchroDecode : Update timers when we decide to decode a picture
 347  *****************************************************************************/
 348 void decoder_SynchroDecode( decoder_synchro_t * p_synchro )
 349 {
 350     p_synchro->decoding_start = mdate();
 351     p_synchro->i_nb_ref = p_synchro->i_dec_nb_ref;
 352 }
 353
 354 /*****************************************************************************
 355  * decoder_SynchroEnd : Called when the image is totally decoded
 356  *****************************************************************************/
 357 void decoder_SynchroEnd( decoder_synchro_t * p_synchro, int i_coding_type,
 358                       vlc_bool_t b_garbage )
 359 {
 360     mtime_t     tau;
 361
 362     if( !b_garbage )
 363     {
 364         tau = mdate() - p_synchro->decoding_start;
 365
 366         /* If duration too high, something happened (pause ?), so don't
 367          * take it into account. */
 368         if( tau < 3 * p_synchro->p_tau[i_coding_type]
 369              || ( !p_synchro->pi_meaningful[i_coding_type]
 370                    && tau < MAX_VALID_TAU ) )
 371         {
 372             /* Mean with average tau, to ensure stability. */
 373             p_synchro->p_tau[i_coding_type] =
 374                 (p_synchro->pi_meaningful[i_coding_type]
 375                  * p_synchro->p_tau[i_coding_type] + tau)
 376                 / (p_synchro->pi_meaningful[i_coding_type] + 1);
 377             if( p_synchro->pi_meaningful[i_coding_type] < MAX_PIC_AVERAGE )
 378             {
 379                 p_synchro->pi_meaningful[i_coding_type]++;
 380             }
 381         }
 382     }
 383 }
 384
 385 /*****************************************************************************
 386  * decoder_SynchroDate : When an image has been decoded, ask for its date
 387  *****************************************************************************/
 388 mtime_t decoder_SynchroDate( decoder_synchro_t * p_synchro )
 389 {
 390     /* No need to lock, since PTS are only used by the video parser. */
 391     return p_synchro->current_pts;
 392 }
 393
 394 /*****************************************************************************
 395  * decoder_SynchroNewPicture: Update stream structure and PTS
 396  *****************************************************************************/
 397 void decoder_SynchroNewPicture( decoder_synchro_t * p_synchro, int i_coding_type,
 398                              int i_repeat_field, mtime_t next_pts,
 399                              mtime_t next_dts, int i_current_rate,
 400                              vlc_bool_t b_low_delay )
 401 {
 402     mtime_t         period = 1000000 * 1001 / p_synchro->i_frame_rate
 403                               * i_current_rate / INPUT_RATE_DEFAULT;
 404 #if 0
 405     mtime_t         now = mdate();
 406 #endif
 407     p_synchro->i_current_rate = i_current_rate;
 408
 409     switch( i_coding_type )
 410     {
 411     case I_CODING_TYPE:
 412         if( p_synchro->i_eta_p
 413              && p_synchro->i_eta_p != p_synchro->i_n_p )
 414         {
 415 #if 0
 416             if( !p_synchro->b_quiet )
 417                 msg_Dbg( p_synchro,
 418                          "stream periodicity changed from P[%d] to P[%d]",
 419                          p_synchro->i_n_p, p_synchro->i_eta_p );
 420 #endif
 421             p_synchro->i_n_p = p_synchro->i_eta_p;
 422         }
 423         p_synchro->i_eta_p = p_synchro->i_eta_b = 0;
 424         p_synchro->i_trash_nb_ref = 0;
 425         if( p_synchro->i_nb_ref < 2 )
 426             p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref + 1;
 427         else
 428             p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref;
 429
 430 #if 0
 431         if( !p_synchro->b_quiet )
 432             msg_Dbg( p_synchro, "I("I64Fd") P("I64Fd")[%d] B("I64Fd")"
 433                   "[%d] YUV("I64Fd") : trashed %d:%d/%d",
 434                   p_synchro->p_tau[I_CODING_TYPE],
 435                   p_synchro->p_tau[P_CODING_TYPE],
 436                   p_synchro->i_n_p,
 437                   p_synchro->p_tau[B_CODING_TYPE],
 438                   p_synchro->i_n_b,
 439                   p_synchro->i_render_time,
 440                   p_synchro->i_not_chosen_pic,
 441                   p_synchro->i_trashed_pic -
 442                   p_synchro->i_not_chosen_pic,
 443                   p_synchro->i_pic );
 444         p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
 445             = p_synchro->i_pic = 0;
 446 #else
 447         if( p_synchro->i_pic >= 100 )
 448         {
 449             if( !p_synchro->b_quiet && p_synchro->i_trashed_pic != 0 )
 450                 msg_Dbg( p_synchro, "decoded %d/%d pictures",
 451                          p_synchro->i_pic
 452                            - p_synchro->i_trashed_pic,
 453                          p_synchro->i_pic );
 454             p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
 455                 = p_synchro->i_pic = 0;
 456         }
 457 #endif
 458         break;
 459
 460     case P_CODING_TYPE:
 461         p_synchro->i_eta_p++;
 462         if( p_synchro->i_eta_b
 463              && p_synchro->i_eta_b != p_synchro->i_n_b )
 464         {
 465 #if 0
 466             if( !p_synchro->b_quiet )
 467                 msg_Dbg( p_synchro,
 468                          "stream periodicity changed from B[%d] to B[%d]",
 469                          p_synchro->i_n_b, p_synchro->i_eta_b );
 470 #endif
 471             p_synchro->i_n_b = p_synchro->i_eta_b;
 472         }
 473         p_synchro->i_eta_b = 0;
 474         p_synchro->i_dec_nb_ref = 2;
 475         p_synchro->i_trash_nb_ref = 0;
 476         break;
 477
 478     case B_CODING_TYPE:
 479         p_synchro->i_eta_b++;
 480         p_synchro->i_dec_nb_ref = p_synchro->i_trash_nb_ref
 481             = p_synchro->i_nb_ref;
 482         break;
 483     }
 484
 485     p_synchro->current_pts += p_synchro->i_current_period
 486                                         * (period >> 1);
 487
 488 #define PTS_THRESHOLD   (period >> 2)
 489     if( i_coding_type == B_CODING_TYPE || b_low_delay )
 490     {
 491         /* A video frame can be displayed 1, 2 or 3 times, according to
 492          * repeat_first_field, top_field_first, progressive_sequence and
 493          * progressive_frame. */
 494         p_synchro->i_current_period = i_repeat_field;
 495
 496         if( next_pts )
 497         {
 498             if( (next_pts - p_synchro->current_pts
 499                     > PTS_THRESHOLD
 500                   || p_synchro->current_pts - next_pts
 501                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
 502             {
 503                 msg_Warn( p_synchro, "decoder synchro warning: pts != "
 504                           "current_date ("I64Fd")",
 505                           p_synchro->current_pts
 506                               - next_pts );
 507             }
 508             p_synchro->current_pts = next_pts;
 509         }
 510     }
 511     else
 512     {
 513         p_synchro->i_current_period = p_synchro->i_backward_period;
 514         p_synchro->i_backward_period = i_repeat_field;
 515
 516         if( p_synchro->backward_pts )
 517         {
 518             if( next_dts &&
 519                 (next_dts - p_synchro->backward_pts
 520                     > PTS_THRESHOLD
 521                   || p_synchro->backward_pts - next_dts
 522                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
 523             {
 524                 msg_Warn( p_synchro, "backward_pts != dts ("I64Fd")",
 525                            next_dts
 526                                - p_synchro->backward_pts );
 527             }
 528             if( (p_synchro->backward_pts - p_synchro->current_pts
 529                     > PTS_THRESHOLD
 530                   || p_synchro->current_pts - p_synchro->backward_pts
 531                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
 532             {
 533                 msg_Warn( p_synchro,
 534                           "backward_pts != current_pts ("I64Fd")",
 535                           p_synchro->current_pts
 536                               - p_synchro->backward_pts );
 537             }
 538             p_synchro->current_pts = p_synchro->backward_pts;
 539             p_synchro->backward_pts = 0;
 540         }
 541         else if( next_dts )
 542         {
 543             if( (next_dts - p_synchro->current_pts
 544                     > PTS_THRESHOLD
 545                   || p_synchro->current_pts - next_dts
 546                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
 547             {
 548                 msg_Warn( p_synchro, "dts != current_pts ("I64Fd")",
 549                           p_synchro->current_pts
 550                               - next_dts );
 551             }
 552             /* By definition of a DTS. */
 553             p_synchro->current_pts = next_dts;
 554             next_dts = 0;
 555         }
 556
 557         if( next_pts )
 558         {
 559             /* Store the PTS for the next time we have to date an I picture. */
 560             p_synchro->backward_pts = next_pts;
 561             next_pts = 0;
 562         }
 563     }
 564 #undef PTS_THRESHOLD
 565
 566 #if 0
 567     /* Removed for incompatibility with slow motion */
 568     if( p_synchro->current_pts + DEFAULT_PTS_DELAY < now )
 569     {
 570         /* We cannot be _that_ late, something must have happened, reinit
 571          * the dates. */
 572         if( !p_synchro->b_quiet )
 573             msg_Warn( p_synchro, "PTS << now ("I64Fd"), resetting",
 574                       now - p_synchro->current_pts - DEFAULT_PTS_DELAY );
 575         p_synchro->current_pts = now + DEFAULT_PTS_DELAY;
 576     }
 577     if( p_synchro->backward_pts
 578          && p_synchro->backward_pts + DEFAULT_PTS_DELAY < now )
 579     {
 580         /* The same. */
 581         p_synchro->backward_pts = 0;
 582     }
 583 #endif
 584
 585     p_synchro->i_pic++;
 586 }