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  * $Id: vpar_synchro.c,v 1.64 2000/12/26 19:14:47 massiot 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 to types of machines :
  59  *      2T > tauP  : machines capable of decoding all P pictures
  60  *      14T > tauI : machines capable of decoding all I pictures
  61  *
  62  * 4. Decoding of an I picture
  63  *    ========================
  64  * On fast machines, we decode all I's.
  65  * Otherwise :
  66  * We can decode an I picture if we simply have enough time to decode it
  67  * before displaying :
  68  *      t0 - t > tau´I + DELTA
  69  *
  70  * 4. Decoding of a P picture
  71  *    =======================
  72  * On fast machines, we decode all P's.
  73  * Otherwise :
  74  * First criterion : have time to decode it.
  75  *      t2 - t > tau´P + DELTA
  76  *
  77  * Second criterion : it shouldn't prevent us from displaying the forthcoming
  78  * I picture, which is more important.
  79  *      t12 - t > tau´P + tau´I + DELTA
  80  *
  81  * 5. Decoding of a B picture
  82  *    =======================
  83  * First criterion : have time to decode it.
  84  *      t1 - t > tau´B + DELTA
  85  *
  86  * Second criterion : it shouldn't prevent us from displaying the forthcoming
  87  * P picture, which is more important.
  88  *      t4 - t > tau´B + tau´P + DELTA
  89  *
  90  * I hope you will have a pleasant flight and do not forget your life
  91  * jacket.
  92  *                                                  --Meuuh (2000-11-09)
  93  */
  94
  95 /*****************************************************************************
  96  * Preamble
  97  *****************************************************************************/
  98 #include "defs.h"
  99
 100 #include "config.h"
 101 #include "common.h"
 102 #include "threads.h"
 103 #include "mtime.h"
 104 #include "plugins.h"
 105
 106 #include "intf_msg.h"
 107
 108 #include "stream_control.h"
 109 #include "input_ext-dec.h"
 110
 111 #include "video.h"
 112 #include "video_output.h"
 113
 114 #include "../video_decoder/vdec_idct.h"
 115 #include "../video_decoder/video_decoder.h"
 116 #include "../video_decoder/vdec_motion.h"
 117
 118 #include "../video_decoder/vpar_blocks.h"
 119 #include "../video_decoder/vpar_headers.h"
 120 #include "../video_decoder/vpar_synchro.h"
 121 #include "../video_decoder/video_parser.h"
 122
 123 #include "main.h"
 124
 125 /*
 126  * Local prototypes
 127  */
 128 static int  SynchroType( void );
 129 static void SynchroNewPicture( vpar_thread_t * p_vpar, int i_coding_type );
 130
 131 /* Error margins */
 132 #define DELTA                   (int)(0.040*CLOCK_FREQ)
 133
 134 #define DEFAULT_NB_P            5
 135 #define DEFAULT_NB_B            1
 136
 137 /*****************************************************************************
 138  * vpar_SynchroInit : You know what ?
 139  *****************************************************************************/
 140 void vpar_SynchroInit( vpar_thread_t * p_vpar )
 141 {
 142     p_vpar->synchro.i_type = SynchroType();
 143     p_vpar->synchro.i_start = p_vpar->synchro.i_end = 0;
 144     vlc_mutex_init( &p_vpar->synchro.fifo_lock );
 145
 146     /* We use a fake stream pattern, which is often right. */
 147     p_vpar->synchro.i_n_p = p_vpar->synchro.i_eta_p = DEFAULT_NB_P;
 148     p_vpar->synchro.i_n_b = p_vpar->synchro.i_eta_b = DEFAULT_NB_B;
 149     memset( p_vpar->synchro.p_tau, 0, 4 * sizeof(mtime_t) );
 150     memset( p_vpar->synchro.pi_meaningful, 0, 4 * sizeof(unsigned int) );
 151     p_vpar->synchro.b_dropped_last = 0;
 152     p_vpar->synchro.current_pts = mdate() + DEFAULT_PTS_DELAY;
 153     p_vpar->synchro.backward_pts = 0;
 154 }
 155
 156 /*****************************************************************************
 157  * vpar_SynchroChoose : Decide whether we will decode a picture or not
 158  *****************************************************************************/
 159 boolean_t vpar_SynchroChoose( vpar_thread_t * p_vpar, int i_coding_type,
 160                               int i_structure )
 161 {
 162     /* For clarity reasons, we separated the special synchros code from the
 163      * mathematical synchro */
 164
 165     if( p_vpar->synchro.i_type != VPAR_SYNCHRO_DEFAULT )
 166     {
 167         switch( i_coding_type )
 168         {
 169         case I_CODING_TYPE:
 170             /* I, IP, IP+, IPB */
 171             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_Iplus )
 172             {
 173                 p_vpar->synchro.b_dropped_last = 1;
 174             }
 175             return( 1 );
 176
 177         case P_CODING_TYPE:
 178             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_I ) /* I */
 179             {
 180                 return( 0 );
 181             }
 182
 183             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_Iplus ) /* I+ */
 184             {
 185                 if( p_vpar->synchro.b_dropped_last )
 186                 {
 187                     p_vpar->synchro.b_dropped_last = 0;
 188                     return( 1 );
 189                 }
 190                 else
 191                 {
 192                     return( 0 );
 193                 }
 194             }
 195
 196             return( 1 ); /* IP, IP+, IPB */
 197
 198         case B_CODING_TYPE:
 199             if( p_vpar->synchro.i_type <= VPAR_SYNCHRO_IP ) /* I, IP */
 200             {
 201                 return( 0 );
 202             }
 203             else if( p_vpar->synchro.i_type == VPAR_SYNCHRO_IPB ) /* IPB */
 204             {
 205                 return( 1 );
 206             }
 207
 208             p_vpar->synchro.b_dropped_last ^= 1; /* IP+ */
 209             return( !p_vpar->synchro.b_dropped_last );
 210         }
 211         return( 0 ); /* never reached but gcc yells at me */
 212     }
 213     else
 214     {
 215 #define TAU_PRIME( coding_type )    (p_vpar->synchro.p_tau[(coding_type)] \
 216                                  + (p_vpar->synchro.p_tau[(coding_type)] >> 1) \
 217                                             + tau_yuv)
 218 #define S                           p_vpar->synchro
 219         /* VPAR_SYNCHRO_DEFAULT */
 220         mtime_t         now, pts, period, tau_yuv;
 221         boolean_t       b_decode = 0;
 222 #ifdef DEBUG_VPAR
 223         char            p_date[MSTRTIME_MAX_SIZE];
 224 #endif
 225
 226         now = mdate();
 227         period = 1000000 / (p_vpar->sequence.i_frame_rate) * 1001;
 228
 229         vlc_mutex_lock( &p_vpar->p_vout->change_lock );
 230         tau_yuv = p_vpar->p_vout->render_time;
 231         vlc_mutex_unlock( &p_vpar->p_vout->change_lock );
 232
 233         vlc_mutex_lock( &p_vpar->synchro.fifo_lock );
 234
 235         switch( i_coding_type )
 236         {
 237         case I_CODING_TYPE:
 238             /* Stream structure changes */
 239             if( S.i_eta_p )
 240                 S.i_n_p = S.i_eta_p;
 241
 242             if( S.backward_pts )
 243             {
 244                 pts = S.backward_pts;
 245             }
 246             else
 247             {
 248                 /* displaying order : B B P B B I
 249                  *                      ^       ^
 250                  *                      |       +- current picture
 251                  *                      +- current PTS
 252                  */
 253                 pts = S.current_pts + period * (S.i_n_b + 2);
 254             }
 255
 256             if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
 257                     S.p_tau[I_CODING_TYPE] )
 258             {
 259                 b_decode = 1;
 260             }
 261             else
 262             {
 263                 b_decode = (pts - now) > (TAU_PRIME(I_CODING_TYPE) + DELTA);
 264             }
 265             if( !b_decode )
 266                 intf_WarnMsg( 3, "vpar synchro warning: trashing I" );
 267             break;
 268
 269         case P_CODING_TYPE:
 270             /* Stream structure changes */
 271             if( S.i_eta_b )
 272                 S.i_n_b = S.i_eta_b;
 273             if( S.i_eta_p + 1 > S.i_n_p )
 274                 S.i_n_p = S.i_eta_p + 1;
 275
 276             if( S.backward_pts )
 277             {
 278                 pts = S.backward_pts;
 279             }
 280             else
 281             {
 282                 pts = S.current_pts + period * (S.i_n_b + 2);
 283             }
 284
 285             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) * (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             /* Stream structure changes */
 312             if( S.i_eta_b + 1 > S.i_n_b )
 313                 S.i_n_b = S.i_eta_b + 1;
 314
 315             pts = S.current_pts + period;
 316
 317             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                 /* Remember that S.i_eta_b is for the moment only eta_b - 1. */
 322                 b_decode &= (pts - now
 323                              + period
 324                              * ( 2 * S.i_n_b - S.i_eta_b + 2))
 325                                > (TAU_PRIME(B_CODING_TYPE)
 326                                    + TAU_PRIME(P_CODING_TYPE) + DELTA);
 327             }
 328             else
 329             {
 330                 b_decode = 0;
 331             }
 332         }
 333
 334         vlc_mutex_unlock( &p_vpar->synchro.fifo_lock );
 335 #ifdef DEBUG_VPAR
 336         intf_DbgMsg("vpar synchro debug: %s picture scheduled for %s, %s (%lld)",
 337                     i_coding_type == B_CODING_TYPE ? "B" :
 338                     (i_coding_type == P_CODING_TYPE ? "P" : "I"),
 339                     mstrtime(p_date, pts), b_decode ? "decoding" : "trashed",
 340                     S.p_tau[i_coding_type]);
 341 #endif
 342         return( b_decode );
 343 #undef S
 344 #undef TAU_PRIME
 345     }
 346 }
 347
 348 /*****************************************************************************
 349  * vpar_SynchroTrash : Update timers when we trash a picture
 350  *****************************************************************************/
 351 void vpar_SynchroTrash( vpar_thread_t * p_vpar, int i_coding_type,
 352                         int i_structure )
 353 {
 354     SynchroNewPicture( p_vpar, i_coding_type );
 355 #ifdef STATS
 356     p_vpar->synchro.i_trashed_pic++;
 357 #endif
 358 }
 359
 360 /*****************************************************************************
 361  * vpar_SynchroDecode : Update timers when we decide to decode a picture
 362  *****************************************************************************/
 363 void vpar_SynchroDecode( vpar_thread_t * p_vpar, int i_coding_type,
 364                          int i_structure )
 365 {
 366     vlc_mutex_lock( &p_vpar->synchro.fifo_lock );
 367
 368     if( ((p_vpar->synchro.i_end + 1 - p_vpar->synchro.i_start)
 369             % MAX_DECODING_PIC) )
 370     {
 371         p_vpar->synchro.p_date_fifo[p_vpar->synchro.i_end] = mdate();
 372         p_vpar->synchro.pi_coding_types[p_vpar->synchro.i_end] = i_coding_type;
 373
 374         FIFO_INCREMENT( i_end );
 375     }
 376     else
 377     {
 378         /* FIFO full, panic() */
 379         intf_ErrMsg("vpar error: synchro fifo full, estimations will be biased");
 380     }
 381     vlc_mutex_unlock( &p_vpar->synchro.fifo_lock );
 382
 383     SynchroNewPicture( p_vpar, i_coding_type );
 384 }
 385
 386 /*****************************************************************************
 387  * vpar_SynchroEnd : Called when the image is totally decoded
 388  *****************************************************************************/
 389 void vpar_SynchroEnd( vpar_thread_t * p_vpar, int i_garbage )
 390 {
 391     mtime_t     tau;
 392     int         i_coding_type;
 393
 394     vlc_mutex_lock( &p_vpar->synchro.fifo_lock );
 395
 396     if (!i_garbage)
 397     {
 398         tau = mdate() - p_vpar->synchro.p_date_fifo[p_vpar->synchro.i_start];
 399         i_coding_type = p_vpar->synchro.pi_coding_types[p_vpar->synchro.i_start];
 400
 401         /* Mean with average tau, to ensure stability. */
 402         p_vpar->synchro.p_tau[i_coding_type] =
 403             (p_vpar->synchro.pi_meaningful[i_coding_type]
 404              * p_vpar->synchro.p_tau[i_coding_type] + tau)
 405             / (p_vpar->synchro.pi_meaningful[i_coding_type] + 1);
 406         if( p_vpar->synchro.pi_meaningful[i_coding_type] < MAX_PIC_AVERAGE )
 407         {
 408             p_vpar->synchro.pi_meaningful[i_coding_type]++;
 409         }
 410 #ifdef DEBUG_VPAR
 411         intf_DbgMsg("vpar synchro debug: finished decoding %s (%lld)",
 412                     i_coding_type == B_CODING_TYPE ? "B" :
 413                     (i_coding_type == P_CODING_TYPE ? "P" : "I"), tau);
 414 #endif
 415     }
 416
 417     FIFO_INCREMENT( i_start );
 418
 419     vlc_mutex_unlock( &p_vpar->synchro.fifo_lock );
 420 }
 421
 422 /*****************************************************************************
 423  * vpar_SynchroDate : When an image has been decoded, ask for its date
 424  *****************************************************************************/
 425 mtime_t vpar_SynchroDate( vpar_thread_t * p_vpar )
 426 {
 427     /* No need to lock, since PTS are only used by the video parser. */
 428     return( p_vpar->synchro.current_pts );
 429 }
 430
 431 /*****************************************************************************
 432  * SynchroType: Get the user's synchro type
 433  *****************************************************************************
 434  * This function is called at initialization.
 435  *****************************************************************************/
 436 static int SynchroType( void )
 437 {
 438     char * psz_synchro = main_GetPszVariable( VPAR_SYNCHRO_VAR, NULL );
 439
 440     if( psz_synchro == NULL )
 441     {
 442         return VPAR_SYNCHRO_DEFAULT;
 443     }
 444
 445     switch( *psz_synchro++ )
 446     {
 447       case 'i':
 448       case 'I':
 449         switch( *psz_synchro++ )
 450         {
 451           case '\0':
 452             return VPAR_SYNCHRO_I;
 453
 454           case '+':
 455             if( *psz_synchro ) return 0;
 456             return VPAR_SYNCHRO_Iplus;
 457
 458           case 'p':
 459           case 'P':
 460             switch( *psz_synchro++ )
 461             {
 462               case '\0':
 463                 return VPAR_SYNCHRO_IP;
 464
 465               case '+':
 466                 if( *psz_synchro ) return 0;
 467                 return VPAR_SYNCHRO_IPplus;
 468
 469               case 'b':
 470               case 'B':
 471                 if( *psz_synchro ) return 0;
 472                 return VPAR_SYNCHRO_IPB;
 473
 474               default:
 475                 return VPAR_SYNCHRO_DEFAULT;
 476
 477             }
 478
 479           default:
 480             return VPAR_SYNCHRO_DEFAULT;
 481         }
 482     }
 483
 484     return VPAR_SYNCHRO_DEFAULT;
 485 }
 486
 487 /*****************************************************************************
 488  * SynchroNewPicture: Update stream structure and PTS
 489  *****************************************************************************/
 490 static void SynchroNewPicture( vpar_thread_t * p_vpar, int i_coding_type )
 491 {
 492     pes_packet_t * p_pes;
 493
 494     switch( i_coding_type )
 495     {
 496     case I_CODING_TYPE:
 497         p_vpar->synchro.i_eta_p = p_vpar->synchro.i_eta_b = 0;
 498         if( p_vpar->synchro.i_eta_p )
 499             p_vpar->synchro.i_n_p = p_vpar->synchro.i_eta_p;
 500 #ifdef STATS
 501         if( p_vpar->synchro.i_type == VPAR_SYNCHRO_DEFAULT )
 502         {
 503             intf_Msg( "vpar synchro stats: I(%lld) P(%lld)[%d] B(%lld)[%d] YUV(%lld) : %d/%d",
 504                   p_vpar->synchro.p_tau[I_CODING_TYPE],
 505                   p_vpar->synchro.p_tau[P_CODING_TYPE],
 506                   p_vpar->synchro.i_n_p,
 507                   p_vpar->synchro.p_tau[B_CODING_TYPE],
 508                   p_vpar->synchro.i_n_b,
 509                   p_vpar->p_vout->render_time,
 510                   p_vpar->synchro.i_pic -
 511                   p_vpar->synchro.i_trashed_pic,
 512                   p_vpar->synchro.i_pic );
 513             p_vpar->synchro.i_trashed_pic = 0;
 514             p_vpar->synchro.i_pic = 0;
 515         }
 516 #endif
 517         break;
 518     case P_CODING_TYPE:
 519         p_vpar->synchro.i_eta_p++;
 520         if( p_vpar->synchro.i_eta_b )
 521             p_vpar->synchro.i_n_b = p_vpar->synchro.i_eta_b;
 522         p_vpar->synchro.i_eta_b = 0;
 523         break;
 524     case B_CODING_TYPE:
 525         p_vpar->synchro.i_eta_b++;
 526         break;
 527     }
 528
 529     p_pes = DECODER_FIFO_START( *p_vpar->bit_stream.p_decoder_fifo );
 530
 531     if( i_coding_type == B_CODING_TYPE )
 532     {
 533         if( p_pes->b_has_pts )
 534         {
 535             if( p_pes->i_pts < p_vpar->synchro.current_pts )
 536             {
 537                 intf_WarnMsg( 2,
 538                         "vpar synchro warning: pts_date < current_date" );
 539             }
 540             p_vpar->synchro.current_pts = p_pes->i_pts;
 541             p_pes->b_has_pts = 0;
 542         }
 543         else
 544         {
 545             p_vpar->synchro.current_pts += 1000000
 546                     / (p_vpar->sequence.i_frame_rate) * 1001;
 547         }
 548     }
 549     else
 550     {
 551         if( p_vpar->synchro.backward_pts == 0 )
 552         {
 553             p_vpar->synchro.current_pts += 1000000
 554                     / (p_vpar->sequence.i_frame_rate) * 1001;
 555         }
 556         else
 557         {
 558             if( p_vpar->synchro.backward_pts < p_vpar->synchro.current_pts )
 559             {
 560                 intf_WarnMsg( 2,
 561                         "vpar warning: backward_date < current_date" );
 562             }
 563             p_vpar->synchro.current_pts = p_vpar->synchro.backward_pts;
 564             p_vpar->synchro.backward_pts = 0;
 565         }
 566
 567         if( p_pes->b_has_pts )
 568         {
 569             /* Store the PTS for the next time we have to date an I picture. */
 570             p_vpar->synchro.backward_pts = p_pes->i_pts;
 571             p_pes->b_has_pts = 0;
 572         }
 573     }
 574
 575 #ifdef STATS
 576     p_vpar->synchro.i_pic++;
 577 #endif
 578 }