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 "input.h"
 112 #include "decoder_fifo.h"
 113 #include "video.h"
 114 #include "video_output.h"
 115
 116 #include "vdec_idct.h"
 117 #include "video_decoder.h"
 118 #include "vdec_motion.h"
 119
 120 #include "vpar_blocks.h"
 121 #include "vpar_headers.h"
 122 #include "vpar_synchro.h"
 123 #include "video_parser.h"
 124
 125 #include "main.h"
 126
 127 /*
 128  * Local prototypes
 129  */
 130 static int  SynchroType( void );
 131 static void SynchroNewPicture( vpar_thread_t * p_vpar, int i_coding_type );
 132
 133 /* Error margins */
 134 #define DELTA                   (int)(0.040*CLOCK_FREQ)
 135
 136 #define DEFAULT_NB_P            5
 137 #define DEFAULT_NB_B            1
 138
 139 /*****************************************************************************
 140  * vpar_SynchroInit : You know what ?
 141  *****************************************************************************/
 142 void vpar_SynchroInit( vpar_thread_t * p_vpar )
 143 {
 144     p_vpar->synchro.i_type = SynchroType();
 145     p_vpar->synchro.i_start = p_vpar->synchro.i_end = 0;
 146     vlc_mutex_init( &p_vpar->synchro.fifo_lock );
 147
 148     /* We use a fake stream pattern, which is often right. */
 149     p_vpar->synchro.i_n_p = p_vpar->synchro.i_eta_p = DEFAULT_NB_P;
 150     p_vpar->synchro.i_n_b = p_vpar->synchro.i_eta_b = DEFAULT_NB_B;
 151     memset( p_vpar->synchro.p_tau, 0, 4 * sizeof(mtime_t) );
 152     memset( p_vpar->synchro.pi_meaningful, 0, 4 * sizeof(unsigned int) );
 153     p_vpar->synchro.b_dropped_last = 0;
 154     p_vpar->synchro.current_pts = mdate() + INPUT_PTS_DELAY;
 155     p_vpar->synchro.backward_pts = 0;
 156 }
 157
 158 /*****************************************************************************
 159  * vpar_SynchroChoose : Decide whether we will decode a picture or not
 160  *****************************************************************************/
 161 boolean_t vpar_SynchroChoose( vpar_thread_t * p_vpar, int i_coding_type,
 162                               int i_structure )
 163 {
 164     /* For clarity reasons, we separated the special synchros code from the
 165      * mathematical synchro */
 166
 167     if( p_vpar->synchro.i_type != VPAR_SYNCHRO_DEFAULT )
 168     {
 169         switch( i_coding_type )
 170         {
 171         case I_CODING_TYPE:
 172             /* I, IP, IP+, IPB */
 173             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_Iplus )
 174             {
 175                 p_vpar->synchro.b_dropped_last = 1;
 176             }
 177             return( 1 );
 178
 179         case P_CODING_TYPE:
 180             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_I ) /* I */
 181             {
 182                 return( 0 );
 183             }
 184
 185             if( p_vpar->synchro.i_type == VPAR_SYNCHRO_Iplus ) /* I+ */
 186             {
 187                 if( p_vpar->synchro.b_dropped_last )
 188                 {
 189                     p_vpar->synchro.b_dropped_last = 0;
 190                     return( 1 );
 191                 }
 192                 else
 193                 {
 194                     return( 0 );
 195                 }
 196             }
 197
 198             return( 1 ); /* IP, IP+, IPB */
 199
 200         case B_CODING_TYPE:
 201             if( p_vpar->synchro.i_type <= VPAR_SYNCHRO_IP ) /* I, IP */
 202             {
 203                 return( 0 );
 204             }
 205             else if( p_vpar->synchro.i_type == VPAR_SYNCHRO_IPB ) /* IPB */
 206             {
 207                 return( 1 );
 208             }
 209
 210             p_vpar->synchro.b_dropped_last ^= 1; /* IP+ */
 211             return( !p_vpar->synchro.b_dropped_last );
 212         }
 213         return( 0 ); /* never reached but gcc yells at me */
 214     }
 215     else
 216     {
 217 #define TAU_PRIME( coding_type )    (p_vpar->synchro.p_tau[(coding_type)] \
 218                                  + (p_vpar->synchro.p_tau[(coding_type)] >> 1) \
 219                                             + tau_yuv)
 220 #define S                           p_vpar->synchro
 221         /* VPAR_SYNCHRO_DEFAULT */
 222         mtime_t         now, pts, period, tau_yuv;
 223         boolean_t       b_decode = 0;
 224
 225         now = mdate();
 226         period = 1000000 / (p_vpar->sequence.i_frame_rate) * 1001;
 227
 228         vlc_mutex_lock( &p_vpar->p_vout->change_lock );
 229         tau_yuv = p_vpar->p_vout->render_time;
 230         vlc_mutex_unlock( &p_vpar->p_vout->change_lock );
 231
 232         vlc_mutex_lock( &p_vpar->synchro.fifo_lock );
 233
 234         switch( i_coding_type )
 235         {
 236         case I_CODING_TYPE:
 237             /* Stream structure changes */
 238             if( S.i_n_p )
 239                 S.i_n_p = S.i_eta_p;
 240
 241             if( S.backward_pts )
 242             {
 243                 pts = S.backward_pts;
 244             }
 245             else
 246             {
 247                 pts = S.current_pts + period * S.i_n_b;
 248             }
 249
 250             b_decode = ( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
 251                            S.p_tau[I_CODING_TYPE] ) ||
 252                        ( (pts - now) > (TAU_PRIME(I_CODING_TYPE) + DELTA) );
 253             if( !b_decode )
 254                 intf_WarnMsg( 3, "vpar synchro warning: trashing I\n" );
 255             break;
 256
 257         case P_CODING_TYPE:
 258             /* Stream structure changes */
 259             if( S.i_n_b )
 260                 S.i_n_b = S.i_eta_b;
 261             if( S.i_eta_p + 1 > S.i_n_p )
 262                 S.i_n_p++;
 263
 264             if( S.backward_pts )
 265             {
 266                 pts = S.backward_pts;
 267             }
 268             else
 269             {
 270                 pts = S.current_pts + period * S.i_n_b;
 271             }
 272
 273             if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
 274             {
 275                 /* Security in case we're _really_ late */
 276                 b_decode = (pts - now > 0);
 277             }
 278             else
 279             {
 280                 b_decode = (pts - now) > (TAU_PRIME(P_CODING_TYPE) + DELTA);
 281                 /* next I */
 282                 b_decode &= (pts - now
 283                               + period
 284                           * ( (S.i_n_p - S.i_eta_p - 1) * (1 + S.i_n_b) - 1 ))
 285                             > (TAU_PRIME(P_CODING_TYPE)
 286                                 + TAU_PRIME(I_CODING_TYPE) + DELTA);
 287             }
 288             break;
 289
 290         case B_CODING_TYPE:
 291             /* Stream structure changes */
 292             if( S.i_eta_b + 1 > S.i_n_b )
 293                 S.i_n_b++;
 294
 295             pts = S.current_pts;
 296
 297             if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
 298             {
 299                 b_decode = (pts - now) > (TAU_PRIME(B_CODING_TYPE) + DELTA);
 300
 301                 /* Remember that S.i_eta_b is for the moment only eta_b - 1. */
 302                 b_decode &= (pts - now
 303                              + period
 304                              * ( 2 * S.i_n_b - S.i_eta_b + 2))
 305                                > (TAU_PRIME(B_CODING_TYPE)
 306                                    + TAU_PRIME(P_CODING_TYPE) + DELTA);
 307             }
 308             else
 309             {
 310                 b_decode = 0;
 311             }
 312         }
 313
 314         vlc_mutex_unlock( &p_vpar->synchro.fifo_lock );
 315         return( b_decode );
 316 #undef S
 317 #undef TAU_PRIME
 318     }
 319 }
 320
 321 /*****************************************************************************
 322  * vpar_SynchroTrash : Update timers when we trash a picture
 323  *****************************************************************************/
 324 void vpar_SynchroTrash( vpar_thread_t * p_vpar, int i_coding_type,
 325                         int i_structure )
 326 {
 327     SynchroNewPicture( p_vpar, i_coding_type );
 328 #ifdef STATS
 329     p_vpar->synchro.i_trashed_pic++;
 330 #endif
 331 }
 332
 333 /*****************************************************************************
 334  * vpar_SynchroDecode : Update timers when we decide to decode a picture
 335  *****************************************************************************/
 336 void vpar_SynchroDecode( vpar_thread_t * p_vpar, int i_coding_type,
 337                          int i_structure )
 338 {
 339     vlc_mutex_lock( &p_vpar->synchro.fifo_lock );
 340
 341     if( ((p_vpar->synchro.i_end + 1 - p_vpar->synchro.i_start)
 342             % MAX_DECODING_PIC) )
 343     {
 344         p_vpar->synchro.p_date_fifo[p_vpar->synchro.i_end] = mdate();
 345         p_vpar->synchro.pi_coding_types[p_vpar->synchro.i_end] = i_coding_type;
 346
 347         FIFO_INCREMENT( i_end );
 348     }
 349     else
 350     {
 351         /* FIFO full, panic() */
 352         intf_ErrMsg("vpar error: synchro fifo full, estimations will be biased\n");
 353     }
 354     vlc_mutex_unlock( &p_vpar->synchro.fifo_lock );
 355
 356     SynchroNewPicture( p_vpar, i_coding_type );
 357 }
 358
 359 /*****************************************************************************
 360  * vpar_SynchroEnd : Called when the image is totally decoded
 361  *****************************************************************************/
 362 void vpar_SynchroEnd( vpar_thread_t * p_vpar, int i_garbage )
 363 {
 364     mtime_t     tau;
 365     int         i_coding_type;
 366
 367     vlc_mutex_lock( &p_vpar->synchro.fifo_lock );
 368
 369     if (!i_garbage)
 370     {
 371         tau = mdate() - p_vpar->synchro.p_date_fifo[p_vpar->synchro.i_start];
 372         i_coding_type = p_vpar->synchro.pi_coding_types[p_vpar->synchro.i_start];
 373
 374         /* Mean with average tau, to ensure stability. */
 375         p_vpar->synchro.p_tau[i_coding_type] =
 376             (p_vpar->synchro.pi_meaningful[i_coding_type]
 377              * p_vpar->synchro.p_tau[i_coding_type] + tau)
 378             / (p_vpar->synchro.pi_meaningful[i_coding_type] + 1);
 379         if( p_vpar->synchro.pi_meaningful[i_coding_type] < MAX_PIC_AVERAGE )
 380         {
 381             p_vpar->synchro.pi_meaningful[i_coding_type]++;
 382         }
 383     }
 384
 385     FIFO_INCREMENT( i_start );
 386
 387     vlc_mutex_unlock( &p_vpar->synchro.fifo_lock );
 388 }
 389
 390 /*****************************************************************************
 391  * vpar_SynchroDate : When an image has been decoded, ask for its date
 392  *****************************************************************************/
 393 mtime_t vpar_SynchroDate( vpar_thread_t * p_vpar )
 394 {
 395     /* No need to lock, since PTS are only used by the video parser. */
 396     return( p_vpar->synchro.current_pts );
 397 }
 398
 399 /*****************************************************************************
 400  * SynchroType: Get the user's synchro type
 401  *****************************************************************************
 402  * This function is called at initialization.
 403  *****************************************************************************/
 404 static int SynchroType( void )
 405 {
 406     char * psz_synchro = main_GetPszVariable( VPAR_SYNCHRO_VAR, NULL );
 407
 408     if( psz_synchro == NULL )
 409     {
 410         return VPAR_SYNCHRO_DEFAULT;
 411     }
 412
 413     switch( *psz_synchro++ )
 414     {
 415       case 'i':
 416       case 'I':
 417         switch( *psz_synchro++ )
 418         {
 419           case '\0':
 420             return VPAR_SYNCHRO_I;
 421
 422           case '+':
 423             if( *psz_synchro ) return 0;
 424             return VPAR_SYNCHRO_Iplus;
 425
 426           case 'p':
 427           case 'P':
 428             switch( *psz_synchro++ )
 429             {
 430               case '\0':
 431                 return VPAR_SYNCHRO_IP;
 432
 433               case '+':
 434                 if( *psz_synchro ) return 0;
 435                 return VPAR_SYNCHRO_IPplus;
 436
 437               case 'b':
 438               case 'B':
 439                 if( *psz_synchro ) return 0;
 440                 return VPAR_SYNCHRO_IPB;
 441
 442               default:
 443                 return VPAR_SYNCHRO_DEFAULT;
 444
 445             }
 446
 447           default:
 448             return VPAR_SYNCHRO_DEFAULT;
 449         }
 450     }
 451
 452     return VPAR_SYNCHRO_DEFAULT;
 453 }
 454
 455 /*****************************************************************************
 456  * SynchroNewPicture: Update stream structure and PTS
 457  *****************************************************************************/
 458 static void SynchroNewPicture( vpar_thread_t * p_vpar, int i_coding_type )
 459 {
 460     pes_packet_t * p_pes;
 461
 462     switch( i_coding_type )
 463     {
 464     case I_CODING_TYPE:
 465         p_vpar->synchro.i_eta_p = p_vpar->synchro.i_eta_b = 0;
 466 #ifdef STATS
 467         if( p_vpar->synchro.i_type == VPAR_SYNCHRO_DEFAULT )
 468         {
 469             intf_Msg( "vpar synchro stats: I(%lld) P(%lld)[%d] B(%lld)[%d] YUV(%lld) : %d/%d\n",
 470                   p_vpar->synchro.p_tau[I_CODING_TYPE],
 471                   p_vpar->synchro.p_tau[P_CODING_TYPE],
 472                   p_vpar->synchro.i_n_p,
 473                   p_vpar->synchro.p_tau[B_CODING_TYPE],
 474                   p_vpar->synchro.i_n_b,
 475                   p_vpar->p_vout->render_time,
 476                   1 + p_vpar->synchro.i_n_p * (1 + p_vpar->synchro.i_n_b) -
 477                   p_vpar->synchro.i_trashed_pic,
 478                   1 + p_vpar->synchro.i_n_p * (1 + p_vpar->synchro.i_n_b) );
 479             p_vpar->synchro.i_trashed_pic = 0;
 480         }
 481 #endif
 482         break;
 483     case P_CODING_TYPE:
 484         p_vpar->synchro.i_eta_b = 0;
 485         p_vpar->synchro.i_eta_p++;
 486         break;
 487     case B_CODING_TYPE:
 488         p_vpar->synchro.i_eta_b++;
 489         break;
 490     }
 491
 492     p_pes = DECODER_FIFO_START( *p_vpar->bit_stream.p_decoder_fifo );
 493
 494     if( i_coding_type == B_CODING_TYPE )
 495     {
 496         if( p_pes->b_has_pts )
 497         {
 498             if( p_pes->i_pts < p_vpar->synchro.current_pts )
 499             {
 500                 intf_WarnMsg( 2,
 501                         "vpar synchro warning: pts_date < current_date\n" );
 502             }
 503             p_vpar->synchro.current_pts = p_pes->i_pts;
 504             p_pes->b_has_pts = 0;
 505         }
 506         else
 507         {
 508             p_vpar->synchro.current_pts += 1000000 / (p_vpar->sequence.i_frame_rate) * 1001;
 509         }
 510     }
 511     else
 512     {
 513         if( p_vpar->synchro.backward_pts == 0 )
 514         {
 515             p_vpar->synchro.current_pts += 1000000 / (p_vpar->sequence.i_frame_rate) * 1001;
 516         }
 517         else
 518         {
 519             if( p_vpar->synchro.backward_pts < p_vpar->synchro.current_pts )
 520             {
 521                 intf_WarnMsg( 2,
 522                         "vpar warning: backward_date < current_date\n" );
 523             }
 524             p_vpar->synchro.current_pts = p_vpar->synchro.backward_pts;
 525             p_vpar->synchro.backward_pts = 0;
 526         }
 527
 528         if( p_pes->b_has_pts )
 529         {
 530             /* Store the PTS for the next time we have to date an I picture. */
 531             p_vpar->synchro.backward_pts = p_pes->i_pts;
 532             p_pes->b_has_pts = 0;
 533         }
 534     }
 535 }