89ef646a2c3d2de8fd56e056623a9b6dc9a6b72c
[vlc.git] / src / input / decoder_synchro.c
1 /*****************************************************************************
2  * decoder_synchro.c : frame dropping routines
3  *****************************************************************************
4  * Copyright (C) 1999-2005 the VideoLAN team
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., 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 #include <vlc/vlc.h>
98 #include <vlc_input.h>
99 #include <vlc_codec_synchro.h>
100
101 /*
102  * Local prototypes
103  */
104
105 #define MAX_PIC_AVERAGE         8
106
107 struct decoder_synchro_t
108 {
109     VLC_COMMON_MEMBERS
110
111     int             i_frame_rate;
112     int             i_current_rate;
113     vlc_bool_t      b_no_skip;
114     vlc_bool_t      b_quiet;
115
116     /* date of the beginning of the decoding of the current picture */
117     mtime_t         decoding_start;
118
119     /* stream properties */
120     unsigned int    i_n_p, i_n_b;
121
122     /* decoding values */
123     mtime_t         p_tau[4];                  /* average decoding durations */
124     unsigned int    pi_meaningful[4];            /* number of durations read */
125
126     /* render_time filled by SynchroChoose() */
127     int i_render_time;
128
129     /* stream context */
130     int             i_nb_ref;                /* Number of reference pictures */
131     int             i_dec_nb_ref;      /* Number of reference pictures we'll *
132                                         * have if we decode the current pic  */
133     int             i_trash_nb_ref;    /* Number of reference pictures we'll *
134                                         * have if we trash the current pic   */
135     unsigned int    i_eta_p, i_eta_b;
136     mtime_t         backward_pts, current_pts;
137     int             i_current_period;   /* period to add to the next picture */
138     int             i_backward_period;  /* period to add after the next
139                                          * reference picture
140                                          * (backward_period * period / 2) */
141
142     /* statistics */
143     unsigned int    i_trashed_pic, i_not_chosen_pic, i_pic;
144 };
145
146 /* Error margins */
147 #define DELTA                   (int)(0.075*CLOCK_FREQ)
148 #define MAX_VALID_TAU           (int)(0.3*CLOCK_FREQ)
149
150 #define DEFAULT_NB_P            5
151 #define DEFAULT_NB_B            1
152
153 /*****************************************************************************
154  * decoder_SynchroInit : You know what ?
155  *****************************************************************************/
156 decoder_synchro_t * decoder_SynchroInit( decoder_t *p_dec,
157                                      int i_frame_rate )
158 {
159     decoder_synchro_t * p_synchro = vlc_object_create( p_dec,
160                                                   sizeof(decoder_synchro_t) );
161     if ( p_synchro == NULL )
162     {
163         msg_Err( p_dec, "out of memory" );
164         return NULL;
165     }
166     vlc_object_attach( p_synchro, p_dec );
167
168     p_synchro->b_no_skip = !config_GetInt( p_dec, "skip-frames" );
169     p_synchro->b_quiet = config_GetInt( p_dec, "quiet-synchro" );
170
171     /* We use a fake stream pattern, which is often right. */
172     p_synchro->i_n_p = p_synchro->i_eta_p = DEFAULT_NB_P;
173     p_synchro->i_n_b = p_synchro->i_eta_b = DEFAULT_NB_B;
174     memset( p_synchro->p_tau, 0, 4 * sizeof(mtime_t) );
175     memset( p_synchro->pi_meaningful, 0, 4 * sizeof(unsigned int) );
176     p_synchro->i_nb_ref = 0;
177     p_synchro->i_trash_nb_ref = p_synchro->i_dec_nb_ref = 0;
178     p_synchro->current_pts = mdate() + DEFAULT_PTS_DELAY;
179     p_synchro->backward_pts = 0;
180     p_synchro->i_current_period = p_synchro->i_backward_period = 0;
181     p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic =
182         p_synchro->i_pic = 0;
183
184     p_synchro->i_frame_rate = i_frame_rate;
185
186     return p_synchro;
187 }
188
189 /*****************************************************************************
190  * decoder_SynchroRelease : You know what ?
191  *****************************************************************************/
192 void decoder_SynchroRelease( decoder_synchro_t * p_synchro )
193 {
194     vlc_object_detach( p_synchro );
195     vlc_object_destroy( 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 vlc_bool_t decoder_SynchroChoose( decoder_synchro_t * p_synchro, int i_coding_type,
211                                int i_render_time, vlc_bool_t 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 = 0;
219     vlc_bool_t      b_decode = 0;
220
221     if ( p_synchro->b_no_skip )
222         return 1;
223
224     now = mdate();
225     period = 1000000 * 1001 / p_synchro->i_frame_rate
226                      * p_synchro->i_current_rate / INPUT_RATE_DEFAULT;
227
228     p_synchro->i_render_time = i_render_time;
229
230     switch( i_coding_type )
231     {
232     case I_CODING_TYPE:
233         if( b_low_delay )
234         {
235             pts = S.current_pts;
236         }
237         else if( S.backward_pts )
238         {
239             pts = S.backward_pts;
240         }
241         else
242         {
243             /* displaying order : B B P B B I
244              *                      ^       ^
245              *                      |       +- current picture
246              *                      +- current PTS
247              */
248             pts = S.current_pts + period * (S.i_n_b + 2);
249         }
250
251         if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
252                 S.p_tau[I_CODING_TYPE] )
253         {
254             b_decode = 1;
255         }
256         else
257         {
258             b_decode = (pts - now) > (TAU_PRIME(I_CODING_TYPE) + DELTA);
259         }
260         if( !b_decode && !p_synchro->b_quiet )
261         {
262             msg_Warn( p_synchro,
263                       "synchro trashing I ("I64Fd")", pts - now );
264         }
265         break;
266
267     case P_CODING_TYPE:
268         if( b_low_delay )
269         {
270             pts = S.current_pts;
271         }
272         else if( S.backward_pts )
273         {
274             pts = S.backward_pts;
275         }
276         else
277         {
278             pts = S.current_pts + period * (S.i_n_b + 1);
279         }
280
281         if( p_synchro->i_nb_ref < 1 )
282         {
283             b_decode = 0;
284         }
285         else 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 + 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         pts = S.current_pts;
312
313         if( p_synchro->i_nb_ref < 2 )
314         {
315             b_decode = 0;
316         }
317         else 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         else
322         {
323             b_decode = 0;
324         }
325     }
326
327     if( !b_decode )
328     {
329         S.i_not_chosen_pic++;
330     }
331     return( b_decode );
332 #undef S
333 #undef TAU_PRIME
334 }
335
336 /*****************************************************************************
337  * decoder_SynchroTrash : Update counters when we trash a picture
338  *****************************************************************************/
339 void decoder_SynchroTrash( decoder_synchro_t * p_synchro )
340 {
341     p_synchro->i_trashed_pic++;
342     p_synchro->i_nb_ref = p_synchro->i_trash_nb_ref;
343 }
344
345 /*****************************************************************************
346  * decoder_SynchroDecode : Update timers when we decide to decode a picture
347  *****************************************************************************/
348 void decoder_SynchroDecode( decoder_synchro_t * p_synchro )
349 {
350     p_synchro->decoding_start = mdate();
351     p_synchro->i_nb_ref = p_synchro->i_dec_nb_ref;
352 }
353
354 /*****************************************************************************
355  * decoder_SynchroEnd : Called when the image is totally decoded
356  *****************************************************************************/
357 void decoder_SynchroEnd( decoder_synchro_t * p_synchro, int i_coding_type,
358                       vlc_bool_t b_garbage )
359 {
360     mtime_t     tau;
361
362     if( !b_garbage )
363     {
364         tau = mdate() - p_synchro->decoding_start;
365
366         /* If duration too high, something happened (pause ?), so don't
367          * take it into account. */
368         if( tau < 3 * p_synchro->p_tau[i_coding_type]
369              || ( !p_synchro->pi_meaningful[i_coding_type]
370                    && tau < MAX_VALID_TAU ) )
371         {
372             /* Mean with average tau, to ensure stability. */
373             p_synchro->p_tau[i_coding_type] =
374                 (p_synchro->pi_meaningful[i_coding_type]
375                  * p_synchro->p_tau[i_coding_type] + tau)
376                 / (p_synchro->pi_meaningful[i_coding_type] + 1);
377             if( p_synchro->pi_meaningful[i_coding_type] < MAX_PIC_AVERAGE )
378             {
379                 p_synchro->pi_meaningful[i_coding_type]++;
380             }
381         }
382     }
383 }
384
385 /*****************************************************************************
386  * decoder_SynchroDate : When an image has been decoded, ask for its date
387  *****************************************************************************/
388 mtime_t decoder_SynchroDate( decoder_synchro_t * p_synchro )
389 {
390     /* No need to lock, since PTS are only used by the video parser. */
391     return p_synchro->current_pts;
392 }
393
394 /*****************************************************************************
395  * decoder_SynchroNewPicture: Update stream structure and PTS
396  *****************************************************************************/
397 void decoder_SynchroNewPicture( decoder_synchro_t * p_synchro, int i_coding_type,
398                              int i_repeat_field, mtime_t next_pts,
399                              mtime_t next_dts, int i_current_rate,
400                              vlc_bool_t b_low_delay )
401 {
402     mtime_t         period = 1000000 * 1001 / p_synchro->i_frame_rate
403                               * i_current_rate / INPUT_RATE_DEFAULT;
404 #if 0
405     mtime_t         now = mdate();
406 #endif
407     p_synchro->i_current_rate = i_current_rate;
408
409     switch( i_coding_type )
410     {
411     case I_CODING_TYPE:
412         if( p_synchro->i_eta_p
413              && p_synchro->i_eta_p != p_synchro->i_n_p )
414         {
415 #if 0
416             if( !p_synchro->b_quiet )
417                 msg_Dbg( p_synchro,
418                          "stream periodicity changed from P[%d] to P[%d]",
419                          p_synchro->i_n_p, p_synchro->i_eta_p );
420 #endif
421             p_synchro->i_n_p = p_synchro->i_eta_p;
422         }
423         p_synchro->i_eta_p = p_synchro->i_eta_b = 0;
424         p_synchro->i_trash_nb_ref = 0;
425         if( p_synchro->i_nb_ref < 2 )
426             p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref + 1;
427         else
428             p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref;
429
430 #if 0
431         if( !p_synchro->b_quiet )
432             msg_Dbg( p_synchro, "I("I64Fd") P("I64Fd")[%d] B("I64Fd")"
433                   "[%d] YUV("I64Fd") : trashed %d:%d/%d",
434                   p_synchro->p_tau[I_CODING_TYPE],
435                   p_synchro->p_tau[P_CODING_TYPE],
436                   p_synchro->i_n_p,
437                   p_synchro->p_tau[B_CODING_TYPE],
438                   p_synchro->i_n_b,
439                   p_synchro->i_render_time,
440                   p_synchro->i_not_chosen_pic,
441                   p_synchro->i_trashed_pic -
442                   p_synchro->i_not_chosen_pic,
443                   p_synchro->i_pic );
444         p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
445             = p_synchro->i_pic = 0;
446 #else
447         if( p_synchro->i_pic >= 100 )
448         {
449             if( !p_synchro->b_quiet && p_synchro->i_trashed_pic != 0 )
450                 msg_Dbg( p_synchro, "decoded %d/%d pictures",
451                          p_synchro->i_pic
452                            - p_synchro->i_trashed_pic,
453                          p_synchro->i_pic );
454             p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
455                 = p_synchro->i_pic = 0;
456         }
457 #endif
458         break;
459
460     case P_CODING_TYPE:
461         p_synchro->i_eta_p++;
462         if( p_synchro->i_eta_b
463              && p_synchro->i_eta_b != p_synchro->i_n_b )
464         {
465 #if 0
466             if( !p_synchro->b_quiet )
467                 msg_Dbg( p_synchro,
468                          "stream periodicity changed from B[%d] to B[%d]",
469                          p_synchro->i_n_b, p_synchro->i_eta_b );
470 #endif
471             p_synchro->i_n_b = p_synchro->i_eta_b;
472         }
473         p_synchro->i_eta_b = 0;
474         p_synchro->i_dec_nb_ref = 2;
475         p_synchro->i_trash_nb_ref = 0;
476         break;
477
478     case B_CODING_TYPE:
479         p_synchro->i_eta_b++;
480         p_synchro->i_dec_nb_ref = p_synchro->i_trash_nb_ref
481             = p_synchro->i_nb_ref;
482         break;
483     }
484
485     p_synchro->current_pts += p_synchro->i_current_period
486                                         * (period >> 1);
487
488 #define PTS_THRESHOLD   (period >> 2)
489     if( i_coding_type == B_CODING_TYPE || b_low_delay )
490     {
491         /* A video frame can be displayed 1, 2 or 3 times, according to
492          * repeat_first_field, top_field_first, progressive_sequence and
493          * progressive_frame. */
494         p_synchro->i_current_period = i_repeat_field;
495
496         if( next_pts )
497         {
498             if( (next_pts - p_synchro->current_pts
499                     > PTS_THRESHOLD
500                   || p_synchro->current_pts - next_pts
501                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
502             {
503                 msg_Warn( p_synchro, "decoder synchro warning: pts != "
504                           "current_date ("I64Fd")",
505                           p_synchro->current_pts
506                               - next_pts );
507             }
508             p_synchro->current_pts = next_pts;
509         }
510     }
511     else
512     {
513         p_synchro->i_current_period = p_synchro->i_backward_period;
514         p_synchro->i_backward_period = i_repeat_field;
515
516         if( p_synchro->backward_pts )
517         {
518             if( next_dts &&
519                 (next_dts - p_synchro->backward_pts
520                     > PTS_THRESHOLD
521                   || p_synchro->backward_pts - next_dts
522                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
523             {
524                 msg_Warn( p_synchro, "backward_pts != dts ("I64Fd")",
525                            next_dts
526                                - p_synchro->backward_pts );
527             }
528             if( (p_synchro->backward_pts - p_synchro->current_pts
529                     > PTS_THRESHOLD
530                   || p_synchro->current_pts - p_synchro->backward_pts
531                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
532             {
533                 msg_Warn( p_synchro,
534                           "backward_pts != current_pts ("I64Fd")",
535                           p_synchro->current_pts
536                               - p_synchro->backward_pts );
537             }
538             p_synchro->current_pts = p_synchro->backward_pts;
539             p_synchro->backward_pts = 0;
540         }
541         else if( next_dts )
542         {
543             if( (next_dts - p_synchro->current_pts
544                     > PTS_THRESHOLD
545                   || p_synchro->current_pts - next_dts
546                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
547             {
548                 msg_Warn( p_synchro, "dts != current_pts ("I64Fd")",
549                           p_synchro->current_pts
550                               - next_dts );
551             }
552             /* By definition of a DTS. */
553             p_synchro->current_pts = next_dts;
554             next_dts = 0;
555         }
556
557         if( next_pts )
558         {
559             /* Store the PTS for the next time we have to date an I picture. */
560             p_synchro->backward_pts = next_pts;
561             next_pts = 0;
562         }
563     }
564 #undef PTS_THRESHOLD
565
566 #if 0
567     /* Removed for incompatibility with slow motion */
568     if( p_synchro->current_pts + DEFAULT_PTS_DELAY < now )
569     {
570         /* We cannot be _that_ late, something must have happened, reinit
571          * the dates. */
572         if( !p_synchro->b_quiet )
573             msg_Warn( p_synchro, "PTS << now ("I64Fd"), resetting",
574                       now - p_synchro->current_pts - DEFAULT_PTS_DELAY );
575         p_synchro->current_pts = now + DEFAULT_PTS_DELAY;
576     }
577     if( p_synchro->backward_pts
578          && p_synchro->backward_pts + DEFAULT_PTS_DELAY < now )
579     {
580         /* The same. */
581         p_synchro->backward_pts = 0;
582     }
583 #endif
584
585     p_synchro->i_pic++;
586 }