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