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[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 #ifdef HAVE_CONFIG_H
98 # include "config.h"
99 #endif
100
101 #include <vlc/vlc.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     int             i_current_rate;
120     vlc_bool_t      b_no_skip;
121     vlc_bool_t      b_quiet;
122
123     /* date of the beginning of the decoding of the current picture */
124     mtime_t         decoding_start;
125
126     /* stream properties */
127     unsigned int    i_n_p, i_n_b;
128
129     /* decoding values */
130     mtime_t         p_tau[4];                  /* average decoding durations */
131     unsigned int    pi_meaningful[4];            /* number of durations read */
132
133     /* render_time filled by SynchroChoose() */
134     int i_render_time;
135
136     /* stream context */
137     int             i_nb_ref;                /* Number of reference pictures */
138     int             i_dec_nb_ref;      /* Number of reference pictures we'll *
139                                         * have if we decode the current pic  */
140     int             i_trash_nb_ref;    /* Number of reference pictures we'll *
141                                         * have if we trash the current pic   */
142     unsigned int    i_eta_p, i_eta_b;
143     mtime_t         backward_pts, current_pts;
144     int             i_current_period;   /* period to add to the next picture */
145     int             i_backward_period;  /* period to add after the next
146                                          * reference picture
147                                          * (backward_period * period / 2) */
148
149     /* statistics */
150     unsigned int    i_trashed_pic, i_not_chosen_pic, i_pic;
151 };
152
153 /* Error margins */
154 #define DELTA                   (int)(0.075*CLOCK_FREQ)
155 #define MAX_VALID_TAU           (int)(0.3*CLOCK_FREQ)
156
157 #define DEFAULT_NB_P            5
158 #define DEFAULT_NB_B            1
159
160 /*****************************************************************************
161  * decoder_SynchroInit : You know what ?
162  *****************************************************************************/
163 decoder_synchro_t * decoder_SynchroInit( decoder_t *p_dec, int i_frame_rate )
164 {
165     decoder_synchro_t * p_synchro = malloc( sizeof(*p_synchro) );
166     if ( p_synchro == NULL )
167     {
168         msg_Err( p_dec, "out of memory" );
169         return NULL;
170     }
171     memset( p_synchro, 0, sizeof(*p_synchro) );
172
173     p_synchro->p_dec = p_dec;
174     p_synchro->b_no_skip = !config_GetInt( p_dec, "skip-frames" );
175     p_synchro->b_quiet = config_GetInt( p_dec, "quiet-synchro" );
176
177     /* We use a fake stream pattern, which is often right. */
178     p_synchro->i_n_p = p_synchro->i_eta_p = DEFAULT_NB_P;
179     p_synchro->i_n_b = p_synchro->i_eta_b = DEFAULT_NB_B;
180     memset( p_synchro->p_tau, 0, 4 * sizeof(mtime_t) );
181     memset( p_synchro->pi_meaningful, 0, 4 * sizeof(unsigned int) );
182     p_synchro->i_nb_ref = 0;
183     p_synchro->i_trash_nb_ref = p_synchro->i_dec_nb_ref = 0;
184     p_synchro->current_pts = mdate() + DEFAULT_PTS_DELAY;
185     p_synchro->backward_pts = 0;
186     p_synchro->i_current_period = p_synchro->i_backward_period = 0;
187     p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic =
188         p_synchro->i_pic = 0;
189
190     p_synchro->i_frame_rate = i_frame_rate;
191
192     return p_synchro;
193 }
194
195 /*****************************************************************************
196  * decoder_SynchroRelease : You know what ?
197  *****************************************************************************/
198 void decoder_SynchroRelease( decoder_synchro_t * p_synchro )
199 {
200     free( p_synchro );
201 }
202
203 /*****************************************************************************
204  * decoder_SynchroReset : Reset the reference picture counter
205  *****************************************************************************/
206 void decoder_SynchroReset( decoder_synchro_t * p_synchro )
207 {
208     p_synchro->i_nb_ref = 0;
209     p_synchro->i_trash_nb_ref = p_synchro->i_dec_nb_ref = 0;
210 }
211
212 /*****************************************************************************
213  * decoder_SynchroChoose : Decide whether we will decode a picture or not
214  *****************************************************************************/
215 vlc_bool_t decoder_SynchroChoose( decoder_synchro_t * p_synchro, int i_coding_type,
216                                int i_render_time, vlc_bool_t b_low_delay )
217 {
218 #define TAU_PRIME( coding_type )    (p_synchro->p_tau[(coding_type)] \
219                                     + (p_synchro->p_tau[(coding_type)] >> 1) \
220                                     + p_synchro->i_render_time)
221 #define S (*p_synchro)
222     mtime_t         now, period;
223     mtime_t         pts = 0;
224     vlc_bool_t      b_decode = 0;
225
226     if ( p_synchro->b_no_skip )
227         return 1;
228
229     now = mdate();
230     period = 1000000 * 1001 / p_synchro->i_frame_rate
231                      * p_synchro->i_current_rate / INPUT_RATE_DEFAULT;
232
233     p_synchro->i_render_time = i_render_time;
234
235     switch( i_coding_type )
236     {
237     case I_CODING_TYPE:
238         if( b_low_delay )
239         {
240             pts = S.current_pts;
241         }
242         else 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 && !p_synchro->b_quiet )
266         {
267             msg_Warn( p_synchro->p_dec,
268                       "synchro trashing I ("I64Fd")", pts - now );
269         }
270         break;
271
272     case P_CODING_TYPE:
273         if( b_low_delay )
274         {
275             pts = S.current_pts;
276         }
277         else if( S.backward_pts )
278         {
279             pts = S.backward_pts;
280         }
281         else
282         {
283             pts = 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         break;
314
315     case B_CODING_TYPE:
316         pts = S.current_pts;
317
318         if( p_synchro->i_nb_ref < 2 )
319         {
320             b_decode = 0;
321         }
322         else if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
323         {
324             b_decode = (pts - now) > (TAU_PRIME(B_CODING_TYPE) + DELTA);
325         }
326         else
327         {
328             b_decode = 0;
329         }
330     }
331
332     if( !b_decode )
333     {
334         S.i_not_chosen_pic++;
335     }
336     return( b_decode );
337 #undef S
338 #undef TAU_PRIME
339 }
340
341 /*****************************************************************************
342  * decoder_SynchroTrash : Update counters when we trash a picture
343  *****************************************************************************/
344 void decoder_SynchroTrash( decoder_synchro_t * p_synchro )
345 {
346     p_synchro->i_trashed_pic++;
347     p_synchro->i_nb_ref = p_synchro->i_trash_nb_ref;
348 }
349
350 /*****************************************************************************
351  * decoder_SynchroDecode : Update timers when we decide to decode a picture
352  *****************************************************************************/
353 void decoder_SynchroDecode( decoder_synchro_t * p_synchro )
354 {
355     p_synchro->decoding_start = mdate();
356     p_synchro->i_nb_ref = p_synchro->i_dec_nb_ref;
357 }
358
359 /*****************************************************************************
360  * decoder_SynchroEnd : Called when the image is totally decoded
361  *****************************************************************************/
362 void decoder_SynchroEnd( decoder_synchro_t * p_synchro, int i_coding_type,
363                       vlc_bool_t b_garbage )
364 {
365     mtime_t     tau;
366
367     if( !b_garbage )
368     {
369         tau = mdate() - p_synchro->decoding_start;
370
371         /* If duration too high, something happened (pause ?), so don't
372          * take it into account. */
373         if( tau < 3 * p_synchro->p_tau[i_coding_type]
374              || ( !p_synchro->pi_meaningful[i_coding_type]
375                    && tau < MAX_VALID_TAU ) )
376         {
377             /* Mean with average tau, to ensure stability. */
378             p_synchro->p_tau[i_coding_type] =
379                 (p_synchro->pi_meaningful[i_coding_type]
380                  * p_synchro->p_tau[i_coding_type] + tau)
381                 / (p_synchro->pi_meaningful[i_coding_type] + 1);
382             if( p_synchro->pi_meaningful[i_coding_type] < MAX_PIC_AVERAGE )
383             {
384                 p_synchro->pi_meaningful[i_coding_type]++;
385             }
386         }
387     }
388 }
389
390 /*****************************************************************************
391  * decoder_SynchroDate : When an image has been decoded, ask for its date
392  *****************************************************************************/
393 mtime_t decoder_SynchroDate( decoder_synchro_t * p_synchro )
394 {
395     /* No need to lock, since PTS are only used by the video parser. */
396     return p_synchro->current_pts;
397 }
398
399 /*****************************************************************************
400  * decoder_SynchroNewPicture: Update stream structure and PTS
401  *****************************************************************************/
402 void decoder_SynchroNewPicture( decoder_synchro_t * p_synchro, int i_coding_type,
403                              int i_repeat_field, mtime_t next_pts,
404                              mtime_t next_dts, int i_current_rate,
405                              vlc_bool_t b_low_delay )
406 {
407     mtime_t         period = 1000000 * 1001 / p_synchro->i_frame_rate
408                               * i_current_rate / INPUT_RATE_DEFAULT;
409 #if 0
410     mtime_t         now = mdate();
411 #endif
412     p_synchro->i_current_rate = i_current_rate;
413
414     switch( i_coding_type )
415     {
416     case I_CODING_TYPE:
417         if( p_synchro->i_eta_p
418              && p_synchro->i_eta_p != p_synchro->i_n_p )
419         {
420 #if 0
421             if( !p_synchro->b_quiet )
422                 msg_Dbg( p_synchro->p_dec,
423                          "stream periodicity changed from P[%d] to P[%d]",
424                          p_synchro->i_n_p, p_synchro->i_eta_p );
425 #endif
426             p_synchro->i_n_p = p_synchro->i_eta_p;
427         }
428         p_synchro->i_eta_p = p_synchro->i_eta_b = 0;
429         p_synchro->i_trash_nb_ref = 0;
430         if( p_synchro->i_nb_ref < 2 )
431             p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref + 1;
432         else
433             p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref;
434
435 #if 0
436         if( !p_synchro->b_quiet )
437             msg_Dbg( p_synchro->p_dec, "I("I64Fd") P("I64Fd")[%d] B("I64Fd")"
438                   "[%d] YUV("I64Fd") : trashed %d:%d/%d",
439                   p_synchro->p_tau[I_CODING_TYPE],
440                   p_synchro->p_tau[P_CODING_TYPE],
441                   p_synchro->i_n_p,
442                   p_synchro->p_tau[B_CODING_TYPE],
443                   p_synchro->i_n_b,
444                   p_synchro->i_render_time,
445                   p_synchro->i_not_chosen_pic,
446                   p_synchro->i_trashed_pic -
447                   p_synchro->i_not_chosen_pic,
448                   p_synchro->i_pic );
449         p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
450             = p_synchro->i_pic = 0;
451 #else
452         if( p_synchro->i_pic >= 100 )
453         {
454             if( !p_synchro->b_quiet && p_synchro->i_trashed_pic != 0 )
455                 msg_Dbg( p_synchro->p_dec, "decoded %d/%d pictures",
456                          p_synchro->i_pic
457                            - p_synchro->i_trashed_pic,
458                          p_synchro->i_pic );
459             p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
460                 = p_synchro->i_pic = 0;
461         }
462 #endif
463         break;
464
465     case P_CODING_TYPE:
466         p_synchro->i_eta_p++;
467         if( p_synchro->i_eta_b
468              && p_synchro->i_eta_b != p_synchro->i_n_b )
469         {
470 #if 0
471             if( !p_synchro->b_quiet )
472                 msg_Dbg( p_synchro->p_dec,
473                          "stream periodicity changed from B[%d] to B[%d]",
474                          p_synchro->i_n_b, p_synchro->i_eta_b );
475 #endif
476             p_synchro->i_n_b = p_synchro->i_eta_b;
477         }
478         p_synchro->i_eta_b = 0;
479         p_synchro->i_dec_nb_ref = 2;
480         p_synchro->i_trash_nb_ref = 0;
481         break;
482
483     case B_CODING_TYPE:
484         p_synchro->i_eta_b++;
485         p_synchro->i_dec_nb_ref = p_synchro->i_trash_nb_ref
486             = p_synchro->i_nb_ref;
487         break;
488     }
489
490     p_synchro->current_pts += p_synchro->i_current_period
491                                         * (period >> 1);
492
493 #define PTS_THRESHOLD   (period >> 2)
494     if( i_coding_type == B_CODING_TYPE || b_low_delay )
495     {
496         /* A video frame can be displayed 1, 2 or 3 times, according to
497          * repeat_first_field, top_field_first, progressive_sequence and
498          * progressive_frame. */
499         p_synchro->i_current_period = i_repeat_field;
500
501         if( next_pts )
502         {
503             if( (next_pts - p_synchro->current_pts
504                     > PTS_THRESHOLD
505                   || p_synchro->current_pts - next_pts
506                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
507             {
508                 msg_Warn( p_synchro->p_dec, "decoder synchro warning: pts != "
509                           "current_date ("I64Fd")",
510                           p_synchro->current_pts
511                               - next_pts );
512             }
513             p_synchro->current_pts = next_pts;
514         }
515     }
516     else
517     {
518         p_synchro->i_current_period = p_synchro->i_backward_period;
519         p_synchro->i_backward_period = i_repeat_field;
520
521         if( p_synchro->backward_pts )
522         {
523             if( next_dts &&
524                 (next_dts - p_synchro->backward_pts
525                     > PTS_THRESHOLD
526                   || p_synchro->backward_pts - next_dts
527                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
528             {
529                 msg_Warn( p_synchro->p_dec, "backward_pts != dts ("I64Fd")",
530                            next_dts
531                                - p_synchro->backward_pts );
532             }
533             if( (p_synchro->backward_pts - p_synchro->current_pts
534                     > PTS_THRESHOLD
535                   || p_synchro->current_pts - p_synchro->backward_pts
536                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
537             {
538                 msg_Warn( p_synchro->p_dec,
539                           "backward_pts != current_pts ("I64Fd")",
540                           p_synchro->current_pts
541                               - p_synchro->backward_pts );
542             }
543             p_synchro->current_pts = p_synchro->backward_pts;
544             p_synchro->backward_pts = 0;
545         }
546         else if( next_dts )
547         {
548             if( (next_dts - p_synchro->current_pts
549                     > PTS_THRESHOLD
550                   || p_synchro->current_pts - next_dts
551                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
552             {
553                 msg_Warn( p_synchro->p_dec, "dts != current_pts ("I64Fd")",
554                           p_synchro->current_pts
555                               - next_dts );
556             }
557             /* By definition of a DTS. */
558             p_synchro->current_pts = next_dts;
559             next_dts = 0;
560         }
561
562         if( next_pts )
563         {
564             /* Store the PTS for the next time we have to date an I picture. */
565             p_synchro->backward_pts = next_pts;
566             next_pts = 0;
567         }
568     }
569 #undef PTS_THRESHOLD
570
571 #if 0
572     /* Removed for incompatibility with slow motion */
573     if( p_synchro->current_pts + DEFAULT_PTS_DELAY < now )
574     {
575         /* We cannot be _that_ late, something must have happened, reinit
576          * the dates. */
577         if( !p_synchro->b_quiet )
578             msg_Warn( p_synchro->p_dec, "PTS << now ("I64Fd"), resetting",
579                       now - p_synchro->current_pts - DEFAULT_PTS_DELAY );
580         p_synchro->current_pts = now + DEFAULT_PTS_DELAY;
581     }
582     if( p_synchro->backward_pts
583          && p_synchro->backward_pts + DEFAULT_PTS_DELAY < now )
584     {
585         /* The same. */
586         p_synchro->backward_pts = 0;
587     }
588 #endif
589
590     p_synchro->i_pic++;
591 }