2d8c021b05bef961a5777cde656012a276854f51
[vlc.git] / src / video_output / vout_synchro.c
1 /*****************************************************************************
2  * vout_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_vout.h>
99 #include <vlc_input.h>
100 #include <vlc_vout_synchro.h>
101
102 /*
103  * Local prototypes
104  */
105
106 /* Error margins */
107 #define DELTA                   (int)(0.075*CLOCK_FREQ)
108 #define MAX_VALID_TAU           (int)(0.3*CLOCK_FREQ)
109
110 #define DEFAULT_NB_P            5
111 #define DEFAULT_NB_B            1
112
113 /*****************************************************************************
114  * vout_SynchroInit : You know what ?
115  *****************************************************************************/
116 vout_synchro_t * __vout_SynchroInit( vlc_object_t * p_object,
117                                      int i_frame_rate )
118 {
119     vout_synchro_t * p_synchro = vlc_object_create( p_object,
120                                                   sizeof(vout_synchro_t) );
121     if ( p_synchro == NULL )
122     {
123         msg_Err( p_object, "out of memory" );
124         return NULL;
125     }
126     vlc_object_attach( p_synchro, p_object );
127
128     p_synchro->b_no_skip = !config_GetInt( p_object, "skip-frames" );
129     p_synchro->b_quiet = config_GetInt( p_object, "quiet-synchro" );
130
131     /* We use a fake stream pattern, which is often right. */
132     p_synchro->i_n_p = p_synchro->i_eta_p = DEFAULT_NB_P;
133     p_synchro->i_n_b = p_synchro->i_eta_b = DEFAULT_NB_B;
134     memset( p_synchro->p_tau, 0, 4 * sizeof(mtime_t) );
135     memset( p_synchro->pi_meaningful, 0, 4 * sizeof(unsigned int) );
136     p_synchro->i_nb_ref = 0;
137     p_synchro->i_trash_nb_ref = p_synchro->i_dec_nb_ref = 0;
138     p_synchro->current_pts = mdate() + DEFAULT_PTS_DELAY;
139     p_synchro->backward_pts = 0;
140     p_synchro->i_current_period = p_synchro->i_backward_period = 0;
141     p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic =
142         p_synchro->i_pic = 0;
143
144     p_synchro->i_frame_rate = i_frame_rate;
145
146     return p_synchro;
147 }
148
149 /*****************************************************************************
150  * vout_SynchroRelease : You know what ?
151  *****************************************************************************/
152 void vout_SynchroRelease( vout_synchro_t * p_synchro )
153 {
154     vlc_object_detach( p_synchro );
155     vlc_object_destroy( p_synchro );
156 }
157
158 /*****************************************************************************
159  * vout_SynchroReset : Reset the reference picture counter
160  *****************************************************************************/
161 void vout_SynchroReset( vout_synchro_t * p_synchro )
162 {
163     p_synchro->i_nb_ref = 0;
164     p_synchro->i_trash_nb_ref = p_synchro->i_dec_nb_ref = 0;
165 }
166
167 /*****************************************************************************
168  * vout_SynchroChoose : Decide whether we will decode a picture or not
169  *****************************************************************************/
170 vlc_bool_t vout_SynchroChoose( vout_synchro_t * p_synchro, int i_coding_type,
171                                int i_render_time, vlc_bool_t b_low_delay )
172 {
173 #define TAU_PRIME( coding_type )    (p_synchro->p_tau[(coding_type)] \
174                                     + (p_synchro->p_tau[(coding_type)] >> 1) \
175                                     + p_synchro->i_render_time)
176 #define S (*p_synchro)
177     mtime_t         now, period;
178     mtime_t         pts = 0;
179     vlc_bool_t      b_decode = 0;
180
181     if ( p_synchro->b_no_skip )
182         return 1;
183
184     now = mdate();
185     period = 1000000 * 1001 / p_synchro->i_frame_rate
186                      * p_synchro->i_current_rate / INPUT_RATE_DEFAULT;
187
188     p_synchro->i_render_time = i_render_time;
189
190     switch( i_coding_type )
191     {
192     case I_CODING_TYPE:
193         if( b_low_delay )
194         {
195             pts = S.current_pts;
196         }
197         else if( S.backward_pts )
198         {
199             pts = S.backward_pts;
200         }
201         else
202         {
203             /* displaying order : B B P B B I
204              *                      ^       ^
205              *                      |       +- current picture
206              *                      +- current PTS
207              */
208             pts = S.current_pts + period * (S.i_n_b + 2);
209         }
210
211         if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
212                 S.p_tau[I_CODING_TYPE] )
213         {
214             b_decode = 1;
215         }
216         else
217         {
218             b_decode = (pts - now) > (TAU_PRIME(I_CODING_TYPE) + DELTA);
219         }
220         if( !b_decode && !p_synchro->b_quiet )
221         {
222             msg_Warn( p_synchro,
223                       "synchro trashing I ("I64Fd")", pts - now );
224         }
225         break;
226
227     case P_CODING_TYPE:
228         if( b_low_delay )
229         {
230             pts = S.current_pts;
231         }
232         else if( S.backward_pts )
233         {
234             pts = S.backward_pts;
235         }
236         else
237         {
238             pts = S.current_pts + period * (S.i_n_b + 1);
239         }
240
241         if( p_synchro->i_nb_ref < 1 )
242         {
243             b_decode = 0;
244         }
245         else if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
246                 S.p_tau[I_CODING_TYPE] )
247         {
248             if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
249             {
250                 /* Security in case we're _really_ late */
251                 b_decode = (pts - now > 0);
252             }
253             else
254             {
255                 b_decode = (pts - now) > (TAU_PRIME(P_CODING_TYPE) + DELTA);
256                 /* next I */
257                 b_decode &= (pts - now
258                               + period
259                           * ( (S.i_n_p - S.i_eta_p) * (1 + S.i_n_b) - 1 ))
260                             > (TAU_PRIME(P_CODING_TYPE)
261                                 + TAU_PRIME(I_CODING_TYPE) + DELTA);
262             }
263         }
264         else
265         {
266             b_decode = 0;
267         }
268         break;
269
270     case B_CODING_TYPE:
271         pts = S.current_pts;
272
273         if( p_synchro->i_nb_ref < 2 )
274         {
275             b_decode = 0;
276         }
277         else if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
278         {
279             b_decode = (pts - now) > (TAU_PRIME(B_CODING_TYPE) + DELTA);
280         }
281         else
282         {
283             b_decode = 0;
284         }
285     }
286
287     if( !b_decode )
288     {
289         S.i_not_chosen_pic++;
290     }
291     return( b_decode );
292 #undef S
293 #undef TAU_PRIME
294 }
295
296 /*****************************************************************************
297  * vout_SynchroTrash : Update counters when we trash a picture
298  *****************************************************************************/
299 void vout_SynchroTrash( vout_synchro_t * p_synchro )
300 {
301     p_synchro->i_trashed_pic++;
302     p_synchro->i_nb_ref = p_synchro->i_trash_nb_ref;
303 }
304
305 /*****************************************************************************
306  * vout_SynchroDecode : Update timers when we decide to decode a picture
307  *****************************************************************************/
308 void vout_SynchroDecode( vout_synchro_t * p_synchro )
309 {
310     p_synchro->decoding_start = mdate();
311     p_synchro->i_nb_ref = p_synchro->i_dec_nb_ref;
312 }
313
314 /*****************************************************************************
315  * vout_SynchroEnd : Called when the image is totally decoded
316  *****************************************************************************/
317 void vout_SynchroEnd( vout_synchro_t * p_synchro, int i_coding_type,
318                       vlc_bool_t b_garbage )
319 {
320     mtime_t     tau;
321
322     if( !b_garbage )
323     {
324         tau = mdate() - p_synchro->decoding_start;
325
326         /* If duration too high, something happened (pause ?), so don't
327          * take it into account. */
328         if( tau < 3 * p_synchro->p_tau[i_coding_type]
329              || ( !p_synchro->pi_meaningful[i_coding_type]
330                    && tau < MAX_VALID_TAU ) )
331         {
332             /* Mean with average tau, to ensure stability. */
333             p_synchro->p_tau[i_coding_type] =
334                 (p_synchro->pi_meaningful[i_coding_type]
335                  * p_synchro->p_tau[i_coding_type] + tau)
336                 / (p_synchro->pi_meaningful[i_coding_type] + 1);
337             if( p_synchro->pi_meaningful[i_coding_type] < MAX_PIC_AVERAGE )
338             {
339                 p_synchro->pi_meaningful[i_coding_type]++;
340             }
341         }
342     }
343 }
344
345 /*****************************************************************************
346  * vout_SynchroDate : When an image has been decoded, ask for its date
347  *****************************************************************************/
348 mtime_t vout_SynchroDate( vout_synchro_t * p_synchro )
349 {
350     /* No need to lock, since PTS are only used by the video parser. */
351     return p_synchro->current_pts;
352 }
353
354 /*****************************************************************************
355  * vout_SynchroNewPicture: Update stream structure and PTS
356  *****************************************************************************/
357 void vout_SynchroNewPicture( vout_synchro_t * p_synchro, int i_coding_type,
358                              int i_repeat_field, mtime_t next_pts,
359                              mtime_t next_dts, int i_current_rate,
360                              vlc_bool_t b_low_delay )
361 {
362     mtime_t         period = 1000000 * 1001 / p_synchro->i_frame_rate
363                               * i_current_rate / INPUT_RATE_DEFAULT;
364 #if 0
365     mtime_t         now = mdate();
366 #endif
367     p_synchro->i_current_rate = i_current_rate;
368
369     switch( i_coding_type )
370     {
371     case I_CODING_TYPE:
372         if( p_synchro->i_eta_p
373              && p_synchro->i_eta_p != p_synchro->i_n_p )
374         {
375 #if 0
376             if( !p_synchro->b_quiet )
377                 msg_Dbg( p_synchro,
378                          "stream periodicity changed from P[%d] to P[%d]",
379                          p_synchro->i_n_p, p_synchro->i_eta_p );
380 #endif
381             p_synchro->i_n_p = p_synchro->i_eta_p;
382         }
383         p_synchro->i_eta_p = p_synchro->i_eta_b = 0;
384         p_synchro->i_trash_nb_ref = 0;
385         if( p_synchro->i_nb_ref < 2 )
386             p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref + 1;
387         else
388             p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref;
389
390 #if 0
391         if( !p_synchro->b_quiet )
392             msg_Dbg( p_synchro, "I("I64Fd") P("I64Fd")[%d] B("I64Fd")"
393                   "[%d] YUV("I64Fd") : trashed %d:%d/%d",
394                   p_synchro->p_tau[I_CODING_TYPE],
395                   p_synchro->p_tau[P_CODING_TYPE],
396                   p_synchro->i_n_p,
397                   p_synchro->p_tau[B_CODING_TYPE],
398                   p_synchro->i_n_b,
399                   p_synchro->i_render_time,
400                   p_synchro->i_not_chosen_pic,
401                   p_synchro->i_trashed_pic -
402                   p_synchro->i_not_chosen_pic,
403                   p_synchro->i_pic );
404         p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
405             = p_synchro->i_pic = 0;
406 #else
407         if( p_synchro->i_pic >= 100 )
408         {
409             if( !p_synchro->b_quiet && p_synchro->i_trashed_pic != 0 )
410                 msg_Dbg( p_synchro, "decoded %d/%d pictures",
411                          p_synchro->i_pic
412                            - p_synchro->i_trashed_pic,
413                          p_synchro->i_pic );
414             p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
415                 = p_synchro->i_pic = 0;
416         }
417 #endif
418         break;
419
420     case P_CODING_TYPE:
421         p_synchro->i_eta_p++;
422         if( p_synchro->i_eta_b
423              && p_synchro->i_eta_b != p_synchro->i_n_b )
424         {
425 #if 0
426             if( !p_synchro->b_quiet )
427                 msg_Dbg( p_synchro,
428                          "stream periodicity changed from B[%d] to B[%d]",
429                          p_synchro->i_n_b, p_synchro->i_eta_b );
430 #endif
431             p_synchro->i_n_b = p_synchro->i_eta_b;
432         }
433         p_synchro->i_eta_b = 0;
434         p_synchro->i_dec_nb_ref = 2;
435         p_synchro->i_trash_nb_ref = 0;
436         break;
437
438     case B_CODING_TYPE:
439         p_synchro->i_eta_b++;
440         p_synchro->i_dec_nb_ref = p_synchro->i_trash_nb_ref
441             = p_synchro->i_nb_ref;
442         break;
443     }
444
445     p_synchro->current_pts += p_synchro->i_current_period
446                                         * (period >> 1);
447
448 #define PTS_THRESHOLD   (period >> 2)
449     if( i_coding_type == B_CODING_TYPE || b_low_delay )
450     {
451         /* A video frame can be displayed 1, 2 or 3 times, according to
452          * repeat_first_field, top_field_first, progressive_sequence and
453          * progressive_frame. */
454         p_synchro->i_current_period = i_repeat_field;
455
456         if( next_pts )
457         {
458             if( (next_pts - p_synchro->current_pts
459                     > PTS_THRESHOLD
460                   || p_synchro->current_pts - next_pts
461                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
462             {
463                 msg_Warn( p_synchro, "vout synchro warning: pts != "
464                           "current_date ("I64Fd")",
465                           p_synchro->current_pts
466                               - next_pts );
467             }
468             p_synchro->current_pts = next_pts;
469         }
470     }
471     else
472     {
473         p_synchro->i_current_period = p_synchro->i_backward_period;
474         p_synchro->i_backward_period = i_repeat_field;
475
476         if( p_synchro->backward_pts )
477         {
478             if( next_dts &&
479                 (next_dts - p_synchro->backward_pts
480                     > PTS_THRESHOLD
481                   || p_synchro->backward_pts - next_dts
482                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
483             {
484                 msg_Warn( p_synchro, "backward_pts != dts ("I64Fd")",
485                            next_dts
486                                - p_synchro->backward_pts );
487             }
488             if( (p_synchro->backward_pts - p_synchro->current_pts
489                     > PTS_THRESHOLD
490                   || p_synchro->current_pts - p_synchro->backward_pts
491                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
492             {
493                 msg_Warn( p_synchro,
494                           "backward_pts != current_pts ("I64Fd")",
495                           p_synchro->current_pts
496                               - p_synchro->backward_pts );
497             }
498             p_synchro->current_pts = p_synchro->backward_pts;
499             p_synchro->backward_pts = 0;
500         }
501         else if( next_dts )
502         {
503             if( (next_dts - p_synchro->current_pts
504                     > PTS_THRESHOLD
505                   || p_synchro->current_pts - next_dts
506                     > PTS_THRESHOLD) && !p_synchro->b_quiet )
507             {
508                 msg_Warn( p_synchro, "dts != current_pts ("I64Fd")",
509                           p_synchro->current_pts
510                               - next_dts );
511             }
512             /* By definition of a DTS. */
513             p_synchro->current_pts = next_dts;
514             next_dts = 0;
515         }
516
517         if( next_pts )
518         {
519             /* Store the PTS for the next time we have to date an I picture. */
520             p_synchro->backward_pts = next_pts;
521             next_pts = 0;
522         }
523     }
524 #undef PTS_THRESHOLD
525
526 #if 0
527     /* Removed for incompatibility with slow motion */
528     if( p_synchro->current_pts + DEFAULT_PTS_DELAY < now )
529     {
530         /* We cannot be _that_ late, something must have happened, reinit
531          * the dates. */
532         if( !p_synchro->b_quiet )
533             msg_Warn( p_synchro, "PTS << now ("I64Fd"), resetting",
534                       now - p_synchro->current_pts - DEFAULT_PTS_DELAY );
535         p_synchro->current_pts = now + DEFAULT_PTS_DELAY;
536     }
537     if( p_synchro->backward_pts
538          && p_synchro->backward_pts + DEFAULT_PTS_DELAY < now )
539     {
540         /* The same. */
541         p_synchro->backward_pts = 0;
542     }
543 #endif
544
545     p_synchro->i_pic++;
546 }