LGPL
[vlc.git] / src / input / decoder_synchro.c
1 /*****************************************************************************
2  * decoder_synchro.c : frame dropping routines
3  *****************************************************************************
4  * Copyright (C) 1999-2005 VLC authors and 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 it
12  * under the terms of the GNU Lesser General Public License as published by
13  * the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
20  *
21  * You should have received a copy of the GNU Lesser General Public License
22  * along with this program; if not, write to the Free Software Foundation,
23  * 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 #ifdef HAVE_CONFIG_H
98 # include "config.h"
99 #endif
100
101 #include <vlc_common.h>
102 #include <vlc_input.h>
103 #include <vlc_codec.h>
104 #include <vlc_codec_synchro.h>
105
106 /*
107  * Local prototypes
108  */
109
110 #define MAX_PIC_AVERAGE         8
111
112 struct decoder_synchro_t
113 {
114     /* */
115     decoder_t       *p_dec;
116
117     /* */
118     int             i_frame_rate;
119     bool            b_no_skip;
120     bool            b_quiet;
121
122     /* date of the beginning of the decoding of the current picture */
123     mtime_t         decoding_start;
124
125     /* stream properties */
126     unsigned int    i_n_p, i_n_b;
127
128     /* decoding values */
129     mtime_t         p_tau[4];                  /* average decoding durations */
130     unsigned int    pi_meaningful[4];            /* number of durations read */
131
132     /* render_time filled by SynchroChoose() */
133     int             i_render_time;
134
135     /* stream context */
136     int             i_nb_ref;                /* Number of reference pictures */
137     int             i_dec_nb_ref;      /* Number of reference pictures we'll *
138                                         * have if we decode the current pic  */
139     int             i_trash_nb_ref;    /* Number of reference pictures we'll *
140                                         * have if we trash the current pic   */
141     unsigned int    i_eta_p, i_eta_b;
142     mtime_t         backward_pts, current_pts;
143     int             i_current_period;   /* period to add to the next picture */
144     int             i_backward_period;  /* period to add after the next
145                                          * reference picture
146                                          * (backward_period * period / 2) */
147
148     /* statistics */
149     unsigned int    i_trashed_pic, i_not_chosen_pic, i_pic;
150 };
151
152 /* Error margins */
153 #define DELTA                   (int)(0.075*CLOCK_FREQ)
154 #define MAX_VALID_TAU           (int)(0.3*CLOCK_FREQ)
155
156 #define DEFAULT_NB_P            5
157 #define DEFAULT_NB_B            1
158
159 /*****************************************************************************
160  * decoder_SynchroInit : You know what ?
161  *****************************************************************************/
162 decoder_synchro_t * decoder_SynchroInit( decoder_t *p_dec, int i_frame_rate )
163 {
164     decoder_synchro_t * p_synchro = calloc( 1, sizeof(*p_synchro) );
165     if( !p_synchro )
166         return NULL;
167
168     p_synchro->p_dec = p_dec;
169     p_synchro->b_no_skip = !var_InheritBool( p_dec, "skip-frames" );
170     p_synchro->b_quiet = var_InheritBool( p_dec, "quiet-synchro" );
171
172     /* We use a fake stream pattern, which is often right. */
173     p_synchro->i_n_p = p_synchro->i_eta_p = DEFAULT_NB_P;
174     p_synchro->i_n_b = p_synchro->i_eta_b = DEFAULT_NB_B;
175     memset( p_synchro->p_tau, 0, 4 * sizeof(mtime_t) );
176     memset( p_synchro->pi_meaningful, 0, 4 * sizeof(unsigned int) );
177     p_synchro->i_nb_ref = 0;
178     p_synchro->i_trash_nb_ref = p_synchro->i_dec_nb_ref = 0;
179     p_synchro->current_pts = 1,
180     p_synchro->backward_pts = 0;
181     p_synchro->i_current_period = p_synchro->i_backward_period = 0;
182     p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic =
183         p_synchro->i_pic = 0;
184
185     p_synchro->i_frame_rate = i_frame_rate;
186
187     return p_synchro;
188 }
189
190 /*****************************************************************************
191  * decoder_SynchroRelease : You know what ?
192  *****************************************************************************/
193 void decoder_SynchroRelease( decoder_synchro_t * p_synchro )
194 {
195     free( 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 bool decoder_SynchroChoose( decoder_synchro_t * p_synchro, int i_coding_type,
211                                int i_render_time, bool 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;
219     bool      b_decode = 0;
220     int       i_current_rate;
221
222     if ( p_synchro->b_no_skip )
223         return 1;
224
225     i_current_rate = decoder_GetDisplayRate( p_synchro->p_dec );
226
227     now = mdate();
228     period = 1000000 * 1001 / p_synchro->i_frame_rate
229                      * i_current_rate / INPUT_RATE_DEFAULT;
230
231     p_synchro->i_render_time = i_render_time;
232
233     switch( i_coding_type )
234     {
235     case I_CODING_TYPE:
236         if( b_low_delay )
237         {
238             pts = decoder_GetDisplayDate( p_synchro->p_dec, S.current_pts );
239         }
240         else if( S.backward_pts )
241         {
242             pts = decoder_GetDisplayDate( p_synchro->p_dec, S.backward_pts );
243         }
244         else
245         {
246             /* displaying order : B B P B B I
247              *                      ^       ^
248              *                      |       +- current picture
249              *                      +- current PTS
250              */
251             pts = decoder_GetDisplayDate( p_synchro->p_dec, S.current_pts ) + period * (S.i_n_b + 2);
252         }
253
254         if( (1 + S.i_n_p * (S.i_n_b + 1)) * period > S.p_tau[I_CODING_TYPE] )
255         {
256             b_decode = 1;
257         }
258         else
259         {
260             b_decode = (pts - now) > (TAU_PRIME(I_CODING_TYPE) + DELTA);
261         }
262         if( pts <= VLC_TS_INVALID )
263             b_decode = 1;
264
265         if( !b_decode && !p_synchro->b_quiet )
266         {
267             msg_Warn( p_synchro->p_dec,
268                       "synchro trashing I (%"PRId64")", pts - now );
269         }
270         break;
271
272     case P_CODING_TYPE:
273         if( b_low_delay )
274         {
275             pts = decoder_GetDisplayDate( p_synchro->p_dec, S.current_pts );
276         }
277         else if( S.backward_pts )
278         {
279             pts = decoder_GetDisplayDate( p_synchro->p_dec, S.backward_pts );
280         }
281         else
282         {
283             pts = decoder_GetDisplayDate( p_synchro->p_dec, S.current_pts + period * (S.i_n_b + 1) );
284         }
285
286         if( p_synchro->i_nb_ref < 1 )
287         {
288             b_decode = 0;
289         }
290         else if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
291                 S.p_tau[I_CODING_TYPE] )
292         {
293             if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
294             {
295                 /* Security in case we're _really_ late */
296                 b_decode = (pts - now > 0);
297             }
298             else
299             {
300                 b_decode = (pts - now) > (TAU_PRIME(P_CODING_TYPE) + DELTA);
301                 /* next I */
302                 b_decode &= (pts - now
303                               + period
304                           * ( (S.i_n_p - S.i_eta_p) * (1 + S.i_n_b) - 1 ))
305                             > (TAU_PRIME(P_CODING_TYPE)
306                                 + TAU_PRIME(I_CODING_TYPE) + DELTA);
307             }
308         }
309         else
310         {
311             b_decode = 0;
312         }
313         if( p_synchro->i_nb_ref >= 1 && pts <= VLC_TS_INVALID )
314             b_decode = 1;
315         break;
316
317     case B_CODING_TYPE:
318         pts = decoder_GetDisplayDate( p_synchro->p_dec, S.current_pts );
319
320         if( p_synchro->i_nb_ref < 2 )
321         {
322             b_decode = 0;
323         }
324         else if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
325         {
326             b_decode = (pts - now) > (TAU_PRIME(B_CODING_TYPE) + DELTA);
327         }
328         else
329         {
330             b_decode = 0;
331         }
332         if( p_synchro->i_nb_ref >= 2 && pts <= VLC_TS_INVALID )
333             b_decode = 1;
334         break;
335     }
336
337     if( !b_decode )
338     {
339         S.i_not_chosen_pic++;
340     }
341     return( b_decode );
342 #undef S
343 #undef TAU_PRIME
344 }
345
346 /*****************************************************************************
347  * decoder_SynchroTrash : Update counters when we trash a picture
348  *****************************************************************************/
349 void decoder_SynchroTrash( decoder_synchro_t * p_synchro )
350 {
351     p_synchro->i_trashed_pic++;
352     p_synchro->i_nb_ref = p_synchro->i_trash_nb_ref;
353 }
354
355 /*****************************************************************************
356  * decoder_SynchroDecode : Update timers when we decide to decode a picture
357  *****************************************************************************/
358 void decoder_SynchroDecode( decoder_synchro_t * p_synchro )
359 {
360     p_synchro->decoding_start = mdate();
361     p_synchro->i_nb_ref = p_synchro->i_dec_nb_ref;
362 }
363
364 /*****************************************************************************
365  * decoder_SynchroEnd : Called when the image is totally decoded
366  *****************************************************************************/
367 void decoder_SynchroEnd( decoder_synchro_t * p_synchro, int i_coding_type,
368                       bool b_garbage )
369 {
370     mtime_t     tau;
371
372     if( !b_garbage )
373     {
374         tau = mdate() - p_synchro->decoding_start;
375
376         /* If duration too high, something happened (pause ?), so don't
377          * take it into account. */
378         if( tau < 3 * p_synchro->p_tau[i_coding_type]
379              || ( !p_synchro->pi_meaningful[i_coding_type]
380                    && tau < MAX_VALID_TAU ) )
381         {
382             /* Mean with average tau, to ensure stability. */
383             p_synchro->p_tau[i_coding_type] =
384                 (p_synchro->pi_meaningful[i_coding_type]
385                  * p_synchro->p_tau[i_coding_type] + tau)
386                 / (p_synchro->pi_meaningful[i_coding_type] + 1);
387             if( p_synchro->pi_meaningful[i_coding_type] < MAX_PIC_AVERAGE )
388             {
389                 p_synchro->pi_meaningful[i_coding_type]++;
390             }
391         }
392     }
393 }
394
395 /*****************************************************************************
396  * decoder_SynchroDate : When an image has been decoded, ask for its date
397  *****************************************************************************/
398 mtime_t decoder_SynchroDate( decoder_synchro_t * p_synchro )
399 {
400     /* No need to lock, since PTS are only used by the video parser. */
401     return p_synchro->current_pts;
402 }
403
404 /*****************************************************************************
405  * decoder_SynchroNewPicture: Update stream structure and PTS
406  *****************************************************************************/
407 void decoder_SynchroNewPicture( decoder_synchro_t * p_synchro, int i_coding_type,
408                                 int i_repeat_field, mtime_t next_pts,
409                                 mtime_t next_dts, bool b_low_delay )
410 {
411     mtime_t         period = 1000000 * 1001 / p_synchro->i_frame_rate;
412 #if 0
413     mtime_t         now = mdate();
414 #endif
415
416     switch( i_coding_type )
417     {
418     case I_CODING_TYPE:
419         if( p_synchro->i_eta_p
420              && p_synchro->i_eta_p != p_synchro->i_n_p )
421         {
422 #if 0
423             if( !p_synchro->b_quiet )
424                 msg_Dbg( p_synchro->p_dec,
425                          "stream periodicity changed from P[%d] to P[%d]",
426                          p_synchro->i_n_p, p_synchro->i_eta_p );
427 #endif
428             p_synchro->i_n_p = p_synchro->i_eta_p;
429         }
430         p_synchro->i_eta_p = p_synchro->i_eta_b = 0;
431         p_synchro->i_trash_nb_ref = 0;
432         if( p_synchro->i_nb_ref < 2 )
433             p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref + 1;
434         else
435             p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref;
436
437 #if 0
438         if( !p_synchro->b_quiet )
439             msg_Dbg( p_synchro->p_dec, "I(%"PRId64") P(%"PRId64")[%d] B(%"PRId64")"
440                   "[%d] YUV(%"PRId64") : trashed %d:%d/%d",
441                   p_synchro->p_tau[I_CODING_TYPE],
442                   p_synchro->p_tau[P_CODING_TYPE],
443                   p_synchro->i_n_p,
444                   p_synchro->p_tau[B_CODING_TYPE],
445                   p_synchro->i_n_b,
446                   p_synchro->i_render_time,
447                   p_synchro->i_not_chosen_pic,
448                   p_synchro->i_trashed_pic -
449                   p_synchro->i_not_chosen_pic,
450                   p_synchro->i_pic );
451         p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
452             = p_synchro->i_pic = 0;
453 #else
454         if( p_synchro->i_pic >= 100 )
455         {
456             if( !p_synchro->b_quiet && p_synchro->i_trashed_pic != 0 )
457                 msg_Dbg( p_synchro->p_dec, "decoded %d/%d pictures",
458                          p_synchro->i_pic
459                            - p_synchro->i_trashed_pic,
460                          p_synchro->i_pic );
461             p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
462                 = p_synchro->i_pic = 0;
463         }
464 #endif
465         break;
466
467     case P_CODING_TYPE:
468         p_synchro->i_eta_p++;
469         if( p_synchro->i_eta_b
470              && p_synchro->i_eta_b != p_synchro->i_n_b )
471         {
472 #if 0
473             if( !p_synchro->b_quiet )
474                 msg_Dbg( p_synchro->p_dec,
475                          "stream periodicity changed from B[%d] to B[%d]",
476                          p_synchro->i_n_b, p_synchro->i_eta_b );
477 #endif
478             p_synchro->i_n_b = p_synchro->i_eta_b;
479         }
480         p_synchro->i_eta_b = 0;
481         p_synchro->i_dec_nb_ref = 2;
482         p_synchro->i_trash_nb_ref = 0;
483         break;
484
485     case B_CODING_TYPE:
486         p_synchro->i_eta_b++;
487         p_synchro->i_dec_nb_ref = p_synchro->i_trash_nb_ref
488             = p_synchro->i_nb_ref;
489         break;
490     }
491
492     p_synchro->current_pts += p_synchro->i_current_period
493                                         * (period >> 1);
494
495 #define PTS_THRESHOLD   (period >> 2)
496     if( i_coding_type == B_CODING_TYPE || b_low_delay )
497     {
498         /* A video frame can be displayed 1, 2 or 3 times, according to
499          * repeat_first_field, top_field_first, progressive_sequence and
500          * progressive_frame. */
501         p_synchro->i_current_period = i_repeat_field;
502
503         if( next_pts )
504         {
505             if( (next_pts - p_synchro->current_pts
506                     > PTS_THRESHOLD
507                   || p_synchro->current_pts - next_pts
508                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
509             {
510                 msg_Warn( p_synchro->p_dec, "decoder synchro warning: pts != "
511                           "current_date (%"PRId64")",
512                           p_synchro->current_pts
513                               - next_pts );
514             }
515             p_synchro->current_pts = next_pts;
516         }
517     }
518     else
519     {
520         p_synchro->i_current_period = p_synchro->i_backward_period;
521         p_synchro->i_backward_period = i_repeat_field;
522
523         if( p_synchro->backward_pts )
524         {
525             if( next_dts &&
526                 (next_dts - p_synchro->backward_pts
527                     > PTS_THRESHOLD
528                   || p_synchro->backward_pts - next_dts
529                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
530             {
531                 msg_Warn( p_synchro->p_dec, "backward_pts != dts (%"PRId64")",
532                            next_dts
533                                - p_synchro->backward_pts );
534             }
535             if( (p_synchro->backward_pts - p_synchro->current_pts
536                     > PTS_THRESHOLD
537                   || p_synchro->current_pts - p_synchro->backward_pts
538                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
539             {
540                 msg_Warn( p_synchro->p_dec,
541                           "backward_pts != current_pts (%"PRId64")",
542                           p_synchro->current_pts
543                               - p_synchro->backward_pts );
544             }
545             p_synchro->current_pts = p_synchro->backward_pts;
546             p_synchro->backward_pts = 0;
547         }
548         else if( next_dts )
549         {
550             if( (next_dts - p_synchro->current_pts
551                     > PTS_THRESHOLD
552                   || p_synchro->current_pts - next_dts
553                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
554             {
555                 msg_Warn( p_synchro->p_dec, "dts != current_pts (%"PRId64")",
556                           p_synchro->current_pts
557                               - next_dts );
558             }
559             /* By definition of a DTS. */
560             p_synchro->current_pts = next_dts;
561             next_dts = 0;
562         }
563
564         if( next_pts )
565         {
566             /* Store the PTS for the next time we have to date an I picture. */
567             p_synchro->backward_pts = next_pts;
568             next_pts = 0;
569         }
570     }
571 #undef PTS_THRESHOLD
572
573 #if 0
574     /* Removed for incompatibility with slow motion */
575     if( p_synchro->current_pts + DEFAULT_PTS_DELAY < now )
576     {
577         /* We cannot be _that_ late, something must have happened, reinit
578          * the dates. */
579         if( !p_synchro->b_quiet )
580             msg_Warn( p_synchro->p_dec, "PTS << now (%"PRId64"), resetting",
581                       now - p_synchro->current_pts - DEFAULT_PTS_DELAY );
582         p_synchro->current_pts = now + DEFAULT_PTS_DELAY;
583     }
584     if( p_synchro->backward_pts
585          && p_synchro->backward_pts + DEFAULT_PTS_DELAY < now )
586     {
587         /* The same. */
588         p_synchro->backward_pts = 0;
589     }
590 #endif
591
592     p_synchro->i_pic++;
593 }