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

   1 /*****************************************************************************
   2  * vpar_synchro.c : frame dropping routines
   3  *****************************************************************************
   4  * Copyright (C) 1999, 2000 VideoLAN
   5  *
   6  * Authors: Christophe Massiot <massiot@via.ecp.fr>
   7  *          Samuel Hocevar <sam@via.ecp.fr>
   8  *          Jean-Marc Dressler <polux@via.ecp.fr>
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License as published by
  12  * the Free Software Foundation; either version 2 of the License, or
  13  * (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with this program; if not, write to the Free Software
  22  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
  23  *****************************************************************************/
  24
  25 /*
  26  * DISCUSSION : How to Write an efficient Frame-Dropping Algorithm
  27  * ==========
  28  *
  29  * This implementation is based on mathematical and statistical
  30  * developments. Older implementations used an enslavement, considering
  31  * that if we're late when reading an I picture, we will decode one frame
  32  * less. It had a tendancy to derive, and wasn't responsive enough, which
  33  * would have caused trouble with the stream control stuff.
  34  *
  35  * 1. Structure of a picture stream
  36  *    =============================
  37  * Between 2 I's, we have for instance :
  38  *    I   B   P   B   P   B   P   B   P   B   P   B   I
  39  *    t0  t1  t2  t3  t4  t5  t6  t7  t8  t9  t10 t11 t12
  40  * Please bear in mind that B's and IP's will be inverted when displaying
  41  * (decoding order != presentation order). Thus, t1 < t0.
  42  *
  43  * 2. Definitions
  44  *    ===========
  45  * t[0..12]     : Presentation timestamps of pictures 0..12.
  46  * t            : Current timestamp, at the moment of the decoding.
  47  * T            : Picture period, T = 1/frame_rate.
  48  * tau[I,P,B]   : Mean time to decode an [I,P,B] picture.
  49  * tauYUV       : Mean time to render a picture (given by the video_output).
  50  * tau´[I,P,B] = 2 * tau[I,P,B] + tauYUV
  51  *              : Mean time + typical difference (estimated to tau/2, that
  52  *                needs to be confirmed) + render time.
  53  * DELTA        : A given error margin.
  54  *
  55  * 3. General considerations
  56  *    ======================
  57  * We define to types of machines :
  58  *      2T > tauP  : machines capable of decoding all P pictures
  59  *      14T > tauI : machines capable of decoding all I pictures
  60  *
  61  * 4. Decoding of an I picture
  62  *    ========================
  63  * On fast machines, we decode all I's.
  64  * Otherwise :
  65  * We can decode an I picture if we simply have enough time to decode it
  66  * before displaying :
  67  *      t0 - t > tau´I + DELTA
  68  *
  69  * 4. Decoding of a P picture
  70  *    =======================
  71  * On fast machines, we decode all P's.
  72  * Otherwise :
  73  * First criterion : have time to decode it.
  74  *      t2 - t > tau´P + DELTA
  75  *
  76  * Second criterion : it shouldn't prevent us from displaying the forthcoming
  77  * I picture, which is more important.
  78  *      t12 - t > tau´P + tau´I + DELTA
  79  *
  80  * 5. Decoding of a B picture
  81  *    =======================
  82  * First criterion : have time to decode it.
  83  *      t1 - t > tau´B + DELTA
  84  *
  85  * Second criterion : it shouldn't prevent us from displaying the forthcoming
  86  * P picture, which is more important.
  87  *      t4 - t > tau´B + tau´P + DELTA
  88  *
  89  * I hope you will have a pleasant flight and do not forget your life
  90  * jacket.
  91  *                                                  --Meuuh (2000-11-09)
  92  */
  93
  94 /*****************************************************************************
  95  * Preamble
  96  *****************************************************************************/
  97 #include "defs.h"
  98
  99 #include <stdlib.h>                                                /* free() */
 100 #include <sys/types.h>                        /* on BSD, uio.h needs types.h */
 101 #include <sys/uio.h>                                            /* "input.h" */
 102
 103 #include "config.h"
 104 #include "common.h"
 105 #include "threads.h"
 106 #include "mtime.h"
 107 #include "plugins.h"
 108
 109 #include "intf_msg.h"
 110
 111 #include "stream_control.h"
 112 #include "input_ext-dec.h"
 113
 114 #include "video.h"
 115 #include "video_output.h"
 116
 117 #include "vdec_idct.h"
 118 #include "video_decoder.h"
 119 #include "vdec_motion.h"
 120
 121 #include "vpar_blocks.h"
 122 #include "vpar_headers.h"
 123 #include "vpar_synchro.h"
 124 #include "video_parser.h"
 125
 126 #include "main.h"
 127
 128 /*
 129  * Local prototypes
 130  */
 131 static int  SynchroType( void );
 132 static void SynchroNewPicture( vpar_thread_t * p_vpar, int i_coding_type );
 133
 134 /* Error margins */
 135 #define DELTA                   (int)(0.040*CLOCK_FREQ)
 136
 137 #define DEFAULT_NB_P            5
 138 #define DEFAULT_NB_B            1
 139
 140 /*****************************************************************************
 141  * vpar_SynchroInit : You know what ?
 142  *****************************************************************************/
 143 void vpar_SynchroInit( vpar_thread_t * p_vpar )
 144 {
 145     p_vpar->synchro.i_type = SynchroType();
 146     p_vpar->synchro.i_start = p_vpar->synchro.i_end = 0;
 147     vlc_mutex_init( &p_vpar->synchro.fifo_lock );
 148
 149     /* We use a fake stream pattern, which is often right. */
 150     p_vpar->synchro.i_n_p = p_vpar->synchro.i_eta_p = DEFAULT_NB_P;
 151     p_vpar->synchro.i_n_b = p_vpar->synchro.i_eta_b = DEFAULT_NB_B;
 152     memset( p_vpar->synchro.p_tau, 0, 4 * sizeof(mtime_t) );
 153     memset( p_vpar->synchro.pi_meaningful, 0, 4 * sizeof(unsigned int) );
 154     p_vpar->synchro.b_dropped_last = 0;
 155     p_vpar->synchro.current_pts = mdate() + DEFAULT_PTS_DELAY;
 156     p_vpar->synchro.backward_pts = 0;
 157 }
 158
 159 /*****************************************************************************
 160  * vpar_SynchroChoose : Decide whether we will decode a picture or not
 161  *****************************************************************************/
 162 boolean_t vpar_SynchroChoose( vpar_thread_t * p_vpar, int i_coding_type,
 163                               int i_structure )
 164 {
 165     /* For clarity reasons, we separated the special synchros code from the
 166      * mathematical synchro */
 167
 168     if( p_vpar->synchro.i_type != VPAR_SYNCHRO_DEFAULT )
 169     {
 170         switch( i_coding_type )
 171         {
 172         case I_CODING_TYPE:
 173             /* I, IP, IP+, IPB */
 174             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_Iplus )
 175             {
 176                 p_vpar->synchro.b_dropped_last = 1;
 177             }
 178             return( 1 );
 179
 180         case P_CODING_TYPE:
 181             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_I ) /* I */
 182             {
 183                 return( 0 );
 184             }
 185
 186             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_Iplus ) /* I+ */
 187             {
 188                 if( p_vpar->synchro.b_dropped_last )
 189                 {
 190                     p_vpar->synchro.b_dropped_last = 0;
 191                     return( 1 );
 192                 }
 193                 else
 194                 {
 195                     return( 0 );
 196                 }
 197             }
 198
 199             return( 1 ); /* IP, IP+, IPB */
 200
 201         case B_CODING_TYPE:
 202             if( p_vpar->synchro.i_type <= VPAR_SYNCHRO_IP ) /* I, IP */
 203             {
 204                 return( 0 );
 205             }
 206             else if( p_vpar->synchro.i_type == VPAR_SYNCHRO_IPB ) /* IPB */
 207             {
 208                 return( 1 );
 209             }
 210
 211             p_vpar->synchro.b_dropped_last ^= 1; /* IP+ */
 212             return( !p_vpar->synchro.b_dropped_last );
 213         }
 214         return( 0 ); /* never reached but gcc yells at me */
 215     }
 216     else
 217     {
 218 #define TAU_PRIME( coding_type )    (p_vpar->synchro.p_tau[(coding_type)] \
 219                                  + (p_vpar->synchro.p_tau[(coding_type)] >> 1) \
 220                                             + tau_yuv)
 221 #define S                           p_vpar->synchro
 222         /* VPAR_SYNCHRO_DEFAULT */
 223         mtime_t         now, pts, period, tau_yuv;
 224         boolean_t       b_decode = 0;
 225 #ifdef DEBUG_VPAR
 226         char            p_date[MSTRTIME_MAX_SIZE];
 227 #endif
 228
 229         now = mdate();
 230         period = 1000000 / (p_vpar->sequence.i_frame_rate) * 1001;
 231
 232         vlc_mutex_lock( &p_vpar->p_vout->change_lock );
 233         tau_yuv = p_vpar->p_vout->render_time;
 234         vlc_mutex_unlock( &p_vpar->p_vout->change_lock );
 235
 236         vlc_mutex_lock( &p_vpar->synchro.fifo_lock );
 237
 238         switch( i_coding_type )
 239         {
 240         case I_CODING_TYPE:
 241             /* Stream structure changes */
 242             if( S.i_n_p )
 243                 S.i_n_p = S.i_eta_p;
 244
 245             if( S.backward_pts )
 246             {
 247                 pts = S.backward_pts;
 248             }
 249             else
 250             {
 251                 /* displaying order : B B P B B I
 252                  *                      ^       ^
 253                  *                      |       +- current picture
 254                  *                      +- current PTS
 255                  */
 256                 pts = S.current_pts + period * (S.i_n_b + 2);
 257             }
 258
 259             if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
 260                     S.p_tau[I_CODING_TYPE] )
 261             {
 262                 b_decode = 1;
 263             }
 264             else
 265             {
 266                 b_decode = (pts - now) > (TAU_PRIME(I_CODING_TYPE) + DELTA);
 267             }
 268             if( !b_decode )
 269                 intf_WarnMsg( 3, "vpar synchro warning: trashing I\n" );
 270             break;
 271
 272         case P_CODING_TYPE:
 273             /* Stream structure changes */
 274             if( S.i_n_b )
 275                 S.i_n_b = S.i_eta_b;
 276             if( S.i_eta_p + 1 > S.i_n_p )
 277                 S.i_n_p++;
 278
 279             if( S.backward_pts )
 280             {
 281                 pts = S.backward_pts;
 282             }
 283             else
 284             {
 285                 pts = S.current_pts + period * (S.i_n_b + 2);
 286             }
 287
 288             if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
 289                     S.p_tau[I_CODING_TYPE] )
 290             {
 291                 if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
 292                 {
 293                     /* Security in case we're _really_ late */
 294                     b_decode = (pts - now > 0);
 295                 }
 296                 else
 297                 {
 298                     b_decode = (pts - now) > (TAU_PRIME(P_CODING_TYPE) + DELTA);
 299                     /* next I */
 300                     b_decode &= (pts - now
 301                                   + period
 302                               * ( (S.i_n_p - S.i_eta_p - 1) * (1 + S.i_n_b) - 1 ))
 303                                 > (TAU_PRIME(P_CODING_TYPE)
 304                                     + TAU_PRIME(I_CODING_TYPE) + DELTA);
 305                 }
 306             }
 307             else
 308             {
 309                 b_decode = 0;
 310             }
 311             break;
 312
 313         case B_CODING_TYPE:
 314             /* Stream structure changes */
 315             if( S.i_eta_b + 1 > S.i_n_b )
 316                 S.i_n_b++;
 317
 318             pts = S.current_pts + period;
 319
 320             if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
 321             {
 322                 b_decode = (pts - now) > (TAU_PRIME(B_CODING_TYPE) + DELTA);
 323
 324                 /* Remember that S.i_eta_b is for the moment only eta_b - 1. */
 325                 b_decode &= (pts - now
 326                              + period
 327                              * ( 2 * S.i_n_b - S.i_eta_b + 2))
 328                                > (TAU_PRIME(B_CODING_TYPE)
 329                                    + TAU_PRIME(P_CODING_TYPE) + DELTA);
 330             }
 331             else
 332             {
 333                 b_decode = 0;
 334             }
 335         }
 336
 337         vlc_mutex_unlock( &p_vpar->synchro.fifo_lock );
 338 #ifdef DEBUG_VPAR
 339         intf_DbgMsg("vpar synchro debug: %s picture scheduled for %s, %s (%lld)\n",
 340                     i_coding_type == B_CODING_TYPE ? "B" :
 341                     (i_coding_type == P_CODING_TYPE ? "P" : "I"),
 342                     mstrtime(p_date, pts), b_decode ? "decoding" : "trashed",
 343                     S.p_tau[i_coding_type]);
 344 #endif
 345         return( b_decode );
 346 #undef S
 347 #undef TAU_PRIME
 348     }
 349 }
 350
 351 /*****************************************************************************
 352  * vpar_SynchroTrash : Update timers when we trash a picture
 353  *****************************************************************************/
 354 void vpar_SynchroTrash( vpar_thread_t * p_vpar, int i_coding_type,
 355                         int i_structure )
 356 {
 357     SynchroNewPicture( p_vpar, i_coding_type );
 358 #ifdef STATS
 359     p_vpar->synchro.i_trashed_pic++;
 360 #endif
 361 }
 362
 363 /*****************************************************************************
 364  * vpar_SynchroDecode : Update timers when we decide to decode a picture
 365  *****************************************************************************/
 366 void vpar_SynchroDecode( vpar_thread_t * p_vpar, int i_coding_type,
 367                          int i_structure )
 368 {
 369     vlc_mutex_lock( &p_vpar->synchro.fifo_lock );
 370
 371     if( ((p_vpar->synchro.i_end + 1 - p_vpar->synchro.i_start)
 372             % MAX_DECODING_PIC) )
 373     {
 374         p_vpar->synchro.p_date_fifo[p_vpar->synchro.i_end] = mdate();
 375         p_vpar->synchro.pi_coding_types[p_vpar->synchro.i_end] = i_coding_type;
 376
 377         FIFO_INCREMENT( i_end );
 378     }
 379     else
 380     {
 381         /* FIFO full, panic() */
 382         intf_ErrMsg("vpar error: synchro fifo full, estimations will be biased\n");
 383     }
 384     vlc_mutex_unlock( &p_vpar->synchro.fifo_lock );
 385
 386     SynchroNewPicture( p_vpar, i_coding_type );
 387 }
 388
 389 /*****************************************************************************
 390  * vpar_SynchroEnd : Called when the image is totally decoded
 391  *****************************************************************************/
 392 void vpar_SynchroEnd( vpar_thread_t * p_vpar, int i_garbage )
 393 {
 394     mtime_t     tau;
 395     int         i_coding_type;
 396
 397     vlc_mutex_lock( &p_vpar->synchro.fifo_lock );
 398
 399     if (!i_garbage)
 400     {
 401         tau = mdate() - p_vpar->synchro.p_date_fifo[p_vpar->synchro.i_start];
 402         i_coding_type = p_vpar->synchro.pi_coding_types[p_vpar->synchro.i_start];
 403
 404         /* Mean with average tau, to ensure stability. */
 405         p_vpar->synchro.p_tau[i_coding_type] =
 406             (p_vpar->synchro.pi_meaningful[i_coding_type]
 407              * p_vpar->synchro.p_tau[i_coding_type] + tau)
 408             / (p_vpar->synchro.pi_meaningful[i_coding_type] + 1);
 409         if( p_vpar->synchro.pi_meaningful[i_coding_type] < MAX_PIC_AVERAGE )
 410         {
 411             p_vpar->synchro.pi_meaningful[i_coding_type]++;
 412         }
 413 #ifdef DEBUG_VPAR
 414         intf_DbgMsg("vpar synchro debug: finished decoding %s (%lld)\n",
 415                     i_coding_type == B_CODING_TYPE ? "B" :
 416                     (i_coding_type == P_CODING_TYPE ? "P" : "I"), tau);
 417 #endif
 418     }
 419
 420     FIFO_INCREMENT( i_start );
 421
 422     vlc_mutex_unlock( &p_vpar->synchro.fifo_lock );
 423 }
 424
 425 /*****************************************************************************
 426  * vpar_SynchroDate : When an image has been decoded, ask for its date
 427  *****************************************************************************/
 428 mtime_t vpar_SynchroDate( vpar_thread_t * p_vpar )
 429 {
 430     /* No need to lock, since PTS are only used by the video parser. */
 431     return( p_vpar->synchro.current_pts );
 432 }
 433
 434 /*****************************************************************************
 435  * SynchroType: Get the user's synchro type
 436  *****************************************************************************
 437  * This function is called at initialization.
 438  *****************************************************************************/
 439 static int SynchroType( void )
 440 {
 441     char * psz_synchro = main_GetPszVariable( VPAR_SYNCHRO_VAR, NULL );
 442
 443     if( psz_synchro == NULL )
 444     {
 445         return VPAR_SYNCHRO_DEFAULT;
 446     }
 447
 448     switch( *psz_synchro++ )
 449     {
 450       case 'i':
 451       case 'I':
 452         switch( *psz_synchro++ )
 453         {
 454           case '\0':
 455             return VPAR_SYNCHRO_I;
 456
 457           case '+':
 458             if( *psz_synchro ) return 0;
 459             return VPAR_SYNCHRO_Iplus;
 460
 461           case 'p':
 462           case 'P':
 463             switch( *psz_synchro++ )
 464             {
 465               case '\0':
 466                 return VPAR_SYNCHRO_IP;
 467
 468               case '+':
 469                 if( *psz_synchro ) return 0;
 470                 return VPAR_SYNCHRO_IPplus;
 471
 472               case 'b':
 473               case 'B':
 474                 if( *psz_synchro ) return 0;
 475                 return VPAR_SYNCHRO_IPB;
 476
 477               default:
 478                 return VPAR_SYNCHRO_DEFAULT;
 479
 480             }
 481
 482           default:
 483             return VPAR_SYNCHRO_DEFAULT;
 484         }
 485     }
 486
 487     return VPAR_SYNCHRO_DEFAULT;
 488 }
 489
 490 /*****************************************************************************
 491  * SynchroNewPicture: Update stream structure and PTS
 492  *****************************************************************************/
 493 static void SynchroNewPicture( vpar_thread_t * p_vpar, int i_coding_type )
 494 {
 495     pes_packet_t * p_pes;
 496
 497     switch( i_coding_type )
 498     {
 499     case I_CODING_TYPE:
 500         p_vpar->synchro.i_eta_p = p_vpar->synchro.i_eta_b = 0;
 501 #ifdef STATS
 502         if( p_vpar->synchro.i_type == VPAR_SYNCHRO_DEFAULT )
 503         {
 504             intf_Msg( "vpar synchro stats: I(%lld) P(%lld)[%d] B(%lld)[%d] YUV(%lld) : %d/%d\n",
 505                   p_vpar->synchro.p_tau[I_CODING_TYPE],
 506                   p_vpar->synchro.p_tau[P_CODING_TYPE],
 507                   p_vpar->synchro.i_n_p,
 508                   p_vpar->synchro.p_tau[B_CODING_TYPE],
 509                   p_vpar->synchro.i_n_b,
 510                   p_vpar->p_vout->render_time,
 511                   1 + p_vpar->synchro.i_n_p * (1 + p_vpar->synchro.i_n_b) -
 512                   p_vpar->synchro.i_trashed_pic,
 513                   1 + p_vpar->synchro.i_n_p * (1 + p_vpar->synchro.i_n_b) );
 514             p_vpar->synchro.i_trashed_pic = 0;
 515         }
 516 #endif
 517         break;
 518     case P_CODING_TYPE:
 519         p_vpar->synchro.i_eta_b = 0;
 520         p_vpar->synchro.i_eta_p++;
 521         break;
 522     case B_CODING_TYPE:
 523         p_vpar->synchro.i_eta_b++;
 524         break;
 525     }
 526
 527     p_pes = DECODER_FIFO_START( *p_vpar->bit_stream.p_decoder_fifo );
 528
 529     if( i_coding_type == B_CODING_TYPE )
 530     {
 531         if( p_pes->b_has_pts )
 532         {
 533             if( p_pes->i_pts < p_vpar->synchro.current_pts )
 534             {
 535                 intf_WarnMsg( 2,
 536                         "vpar synchro warning: pts_date < current_date\n" );
 537             }
 538             p_vpar->synchro.current_pts = p_pes->i_pts;
 539             p_pes->b_has_pts = 0;
 540         }
 541         else
 542         {
 543             p_vpar->synchro.current_pts += 1000000 / (p_vpar->sequence.i_frame_rate) * 1001;
 544         }
 545     }
 546     else
 547     {
 548         if( p_vpar->synchro.backward_pts == 0 )
 549         {
 550             p_vpar->synchro.current_pts += 1000000 / (p_vpar->sequence.i_frame_rate) * 1001;
 551         }
 552         else
 553         {
 554             if( p_vpar->synchro.backward_pts < p_vpar->synchro.current_pts )
 555             {
 556                 intf_WarnMsg( 2,
 557                         "vpar warning: backward_date < current_date\n" );
 558             }
 559             p_vpar->synchro.current_pts = p_vpar->synchro.backward_pts;
 560             p_vpar->synchro.backward_pts = 0;
 561         }
 562
 563         if( p_pes->b_has_pts )
 564         {
 565             /* Store the PTS for the next time we have to date an I picture. */
 566             p_vpar->synchro.backward_pts = p_pes->i_pts;
 567             p_pes->b_has_pts = 0;
 568         }
 569     }
 570 }