1 /*****************************************************************************
2 * decoder_synchro.c : frame dropping routines
3 *****************************************************************************
4 * Copyright (C) 1999-2005 the VideoLAN team
7 * Authors: Christophe Massiot <massiot@via.ecp.fr>
8 * Samuel Hocevar <sam@via.ecp.fr>
9 * Jean-Marc Dressler <polux@via.ecp.fr>
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.
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.
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 *****************************************************************************/
27 * DISCUSSION : How to Write an efficient Frame-Dropping Algorithm
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.
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.
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.
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
63 * 4. Decoding of an I picture
64 * ========================
65 * On fast machines, we decode all I's.
67 * We can decode an I picture if we simply have enough time to decode it
69 * t0 - t > tau´I + DELTA
71 * 5. Decoding of a P picture
72 * =======================
73 * On fast machines, we decode all P's.
75 * First criterion : have time to decode it.
76 * t2 - t > tau´P + DELTA
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
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
89 * I hope you will have a pleasant flight and do not forget your life
91 * --Meuuh (2000-12-29)
94 /*****************************************************************************
96 *****************************************************************************/
101 #include <vlc_common.h>
102 #include <vlc_input.h>
103 #include <vlc_codec.h>
104 #include <vlc_codec_synchro.h>
110 #define MAX_PIC_AVERAGE 8
112 struct decoder_synchro_t
122 /* date of the beginning of the decoding of the current picture */
123 mtime_t decoding_start;
125 /* stream properties */
126 unsigned int i_n_p, i_n_b;
128 /* decoding values */
129 mtime_t p_tau[4]; /* average decoding durations */
130 unsigned int pi_meaningful[4]; /* number of durations read */
132 /* render_time filled by SynchroChoose() */
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
146 * (backward_period * period / 2) */
149 unsigned int i_trashed_pic, i_not_chosen_pic, i_pic;
153 #define DELTA (int)(0.075*CLOCK_FREQ)
154 #define MAX_VALID_TAU (int)(0.3*CLOCK_FREQ)
156 #define DEFAULT_NB_P 5
157 #define DEFAULT_NB_B 1
159 /*****************************************************************************
160 * decoder_SynchroInit : You know what ?
161 *****************************************************************************/
162 decoder_synchro_t * decoder_SynchroInit( decoder_t *p_dec, int i_frame_rate )
164 decoder_synchro_t * p_synchro = malloc( sizeof(*p_synchro) );
165 if ( p_synchro == NULL )
167 memset( p_synchro, 0, sizeof(*p_synchro) );
169 p_synchro->p_dec = p_dec;
170 p_synchro->b_no_skip = !config_GetInt( p_dec, "skip-frames" );
171 p_synchro->b_quiet = config_GetInt( p_dec, "quiet-synchro" );
173 /* We use a fake stream pattern, which is often right. */
174 p_synchro->i_n_p = p_synchro->i_eta_p = DEFAULT_NB_P;
175 p_synchro->i_n_b = p_synchro->i_eta_b = DEFAULT_NB_B;
176 memset( p_synchro->p_tau, 0, 4 * sizeof(mtime_t) );
177 memset( p_synchro->pi_meaningful, 0, 4 * sizeof(unsigned int) );
178 p_synchro->i_nb_ref = 0;
179 p_synchro->i_trash_nb_ref = p_synchro->i_dec_nb_ref = 0;
180 p_synchro->current_pts = 1,
181 p_synchro->backward_pts = 0;
182 p_synchro->i_current_period = p_synchro->i_backward_period = 0;
183 p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic =
184 p_synchro->i_pic = 0;
186 p_synchro->i_frame_rate = i_frame_rate;
191 /*****************************************************************************
192 * decoder_SynchroRelease : You know what ?
193 *****************************************************************************/
194 void decoder_SynchroRelease( decoder_synchro_t * p_synchro )
199 /*****************************************************************************
200 * decoder_SynchroReset : Reset the reference picture counter
201 *****************************************************************************/
202 void decoder_SynchroReset( decoder_synchro_t * p_synchro )
204 p_synchro->i_nb_ref = 0;
205 p_synchro->i_trash_nb_ref = p_synchro->i_dec_nb_ref = 0;
208 /*****************************************************************************
209 * decoder_SynchroChoose : Decide whether we will decode a picture or not
210 *****************************************************************************/
211 bool decoder_SynchroChoose( decoder_synchro_t * p_synchro, int i_coding_type,
212 int i_render_time, bool b_low_delay )
214 #define TAU_PRIME( coding_type ) (p_synchro->p_tau[(coding_type)] \
215 + (p_synchro->p_tau[(coding_type)] >> 1) \
216 + p_synchro->i_render_time)
217 #define S (*p_synchro)
223 if ( p_synchro->b_no_skip )
226 i_current_rate = decoder_GetDisplayRate( p_synchro->p_dec );
229 period = 1000000 * 1001 / p_synchro->i_frame_rate
230 * i_current_rate / INPUT_RATE_DEFAULT;
232 p_synchro->i_render_time = i_render_time;
234 switch( i_coding_type )
239 pts = decoder_GetDisplayDate( p_synchro->p_dec, S.current_pts );
241 else if( S.backward_pts )
243 pts = decoder_GetDisplayDate( p_synchro->p_dec, S.backward_pts );
247 /* displaying order : B B P B B I
249 * | +- current picture
252 pts = decoder_GetDisplayDate( p_synchro->p_dec, S.current_pts ) + period * (S.i_n_b + 2);
255 if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
256 S.p_tau[I_CODING_TYPE] )
262 b_decode = (pts - now) > (TAU_PRIME(I_CODING_TYPE) + DELTA);
264 if( !b_decode && !p_synchro->b_quiet )
266 msg_Warn( p_synchro->p_dec,
267 "synchro trashing I (%"PRId64")", pts - now );
274 pts = decoder_GetDisplayDate( p_synchro->p_dec, S.current_pts );
276 else if( S.backward_pts )
278 pts = decoder_GetDisplayDate( p_synchro->p_dec, S.backward_pts );
282 pts = decoder_GetDisplayDate( p_synchro->p_dec, S.current_pts + period * (S.i_n_b + 1) );
285 if( p_synchro->i_nb_ref < 1 )
289 else if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
290 S.p_tau[I_CODING_TYPE] )
292 if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
294 /* Security in case we're _really_ late */
295 b_decode = (pts - now > 0);
299 b_decode = (pts - now) > (TAU_PRIME(P_CODING_TYPE) + DELTA);
301 b_decode &= (pts - now
303 * ( (S.i_n_p - S.i_eta_p) * (1 + S.i_n_b) - 1 ))
304 > (TAU_PRIME(P_CODING_TYPE)
305 + TAU_PRIME(I_CODING_TYPE) + DELTA);
315 pts = decoder_GetDisplayDate( p_synchro->p_dec, S.current_pts );
317 if( p_synchro->i_nb_ref < 2 )
321 else if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
323 b_decode = (pts - now) > (TAU_PRIME(B_CODING_TYPE) + DELTA);
333 S.i_not_chosen_pic++;
340 /*****************************************************************************
341 * decoder_SynchroTrash : Update counters when we trash a picture
342 *****************************************************************************/
343 void decoder_SynchroTrash( decoder_synchro_t * p_synchro )
345 p_synchro->i_trashed_pic++;
346 p_synchro->i_nb_ref = p_synchro->i_trash_nb_ref;
349 /*****************************************************************************
350 * decoder_SynchroDecode : Update timers when we decide to decode a picture
351 *****************************************************************************/
352 void decoder_SynchroDecode( decoder_synchro_t * p_synchro )
354 p_synchro->decoding_start = mdate();
355 p_synchro->i_nb_ref = p_synchro->i_dec_nb_ref;
358 /*****************************************************************************
359 * decoder_SynchroEnd : Called when the image is totally decoded
360 *****************************************************************************/
361 void decoder_SynchroEnd( decoder_synchro_t * p_synchro, int i_coding_type,
368 tau = mdate() - p_synchro->decoding_start;
370 /* If duration too high, something happened (pause ?), so don't
371 * take it into account. */
372 if( tau < 3 * p_synchro->p_tau[i_coding_type]
373 || ( !p_synchro->pi_meaningful[i_coding_type]
374 && tau < MAX_VALID_TAU ) )
376 /* Mean with average tau, to ensure stability. */
377 p_synchro->p_tau[i_coding_type] =
378 (p_synchro->pi_meaningful[i_coding_type]
379 * p_synchro->p_tau[i_coding_type] + tau)
380 / (p_synchro->pi_meaningful[i_coding_type] + 1);
381 if( p_synchro->pi_meaningful[i_coding_type] < MAX_PIC_AVERAGE )
383 p_synchro->pi_meaningful[i_coding_type]++;
389 /*****************************************************************************
390 * decoder_SynchroDate : When an image has been decoded, ask for its date
391 *****************************************************************************/
392 mtime_t decoder_SynchroDate( decoder_synchro_t * p_synchro )
394 /* No need to lock, since PTS are only used by the video parser. */
395 return p_synchro->current_pts;
398 /*****************************************************************************
399 * decoder_SynchroNewPicture: Update stream structure and PTS
400 *****************************************************************************/
401 void decoder_SynchroNewPicture( decoder_synchro_t * p_synchro, int i_coding_type,
402 int i_repeat_field, mtime_t next_pts,
403 mtime_t next_dts, bool b_low_delay )
405 mtime_t period = 1000000 * 1001 / p_synchro->i_frame_rate;
407 mtime_t now = mdate();
410 switch( i_coding_type )
413 if( p_synchro->i_eta_p
414 && p_synchro->i_eta_p != p_synchro->i_n_p )
417 if( !p_synchro->b_quiet )
418 msg_Dbg( p_synchro->p_dec,
419 "stream periodicity changed from P[%d] to P[%d]",
420 p_synchro->i_n_p, p_synchro->i_eta_p );
422 p_synchro->i_n_p = p_synchro->i_eta_p;
424 p_synchro->i_eta_p = p_synchro->i_eta_b = 0;
425 p_synchro->i_trash_nb_ref = 0;
426 if( p_synchro->i_nb_ref < 2 )
427 p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref + 1;
429 p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref;
432 if( !p_synchro->b_quiet )
433 msg_Dbg( p_synchro->p_dec, "I(%"PRId64") P(%"PRId64")[%d] B(%"PRId64")"
434 "[%d] YUV(%"PRId64") : trashed %d:%d/%d",
435 p_synchro->p_tau[I_CODING_TYPE],
436 p_synchro->p_tau[P_CODING_TYPE],
438 p_synchro->p_tau[B_CODING_TYPE],
440 p_synchro->i_render_time,
441 p_synchro->i_not_chosen_pic,
442 p_synchro->i_trashed_pic -
443 p_synchro->i_not_chosen_pic,
445 p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
446 = p_synchro->i_pic = 0;
448 if( p_synchro->i_pic >= 100 )
450 if( !p_synchro->b_quiet && p_synchro->i_trashed_pic != 0 )
451 msg_Dbg( p_synchro->p_dec, "decoded %d/%d pictures",
453 - p_synchro->i_trashed_pic,
455 p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
456 = p_synchro->i_pic = 0;
462 p_synchro->i_eta_p++;
463 if( p_synchro->i_eta_b
464 && p_synchro->i_eta_b != p_synchro->i_n_b )
467 if( !p_synchro->b_quiet )
468 msg_Dbg( p_synchro->p_dec,
469 "stream periodicity changed from B[%d] to B[%d]",
470 p_synchro->i_n_b, p_synchro->i_eta_b );
472 p_synchro->i_n_b = p_synchro->i_eta_b;
474 p_synchro->i_eta_b = 0;
475 p_synchro->i_dec_nb_ref = 2;
476 p_synchro->i_trash_nb_ref = 0;
480 p_synchro->i_eta_b++;
481 p_synchro->i_dec_nb_ref = p_synchro->i_trash_nb_ref
482 = p_synchro->i_nb_ref;
486 p_synchro->current_pts += p_synchro->i_current_period
489 #define PTS_THRESHOLD (period >> 2)
490 if( i_coding_type == B_CODING_TYPE || b_low_delay )
492 /* A video frame can be displayed 1, 2 or 3 times, according to
493 * repeat_first_field, top_field_first, progressive_sequence and
494 * progressive_frame. */
495 p_synchro->i_current_period = i_repeat_field;
499 if( (next_pts - p_synchro->current_pts
501 || p_synchro->current_pts - next_pts
502 > PTS_THRESHOLD) && !p_synchro->b_quiet )
504 msg_Warn( p_synchro->p_dec, "decoder synchro warning: pts != "
505 "current_date (%"PRId64")",
506 p_synchro->current_pts
509 p_synchro->current_pts = next_pts;
514 p_synchro->i_current_period = p_synchro->i_backward_period;
515 p_synchro->i_backward_period = i_repeat_field;
517 if( p_synchro->backward_pts )
520 (next_dts - p_synchro->backward_pts
522 || p_synchro->backward_pts - next_dts
523 > PTS_THRESHOLD) && !p_synchro->b_quiet )
525 msg_Warn( p_synchro->p_dec, "backward_pts != dts (%"PRId64")",
527 - p_synchro->backward_pts );
529 if( (p_synchro->backward_pts - p_synchro->current_pts
531 || p_synchro->current_pts - p_synchro->backward_pts
532 > PTS_THRESHOLD) && !p_synchro->b_quiet )
534 msg_Warn( p_synchro->p_dec,
535 "backward_pts != current_pts (%"PRId64")",
536 p_synchro->current_pts
537 - p_synchro->backward_pts );
539 p_synchro->current_pts = p_synchro->backward_pts;
540 p_synchro->backward_pts = 0;
544 if( (next_dts - p_synchro->current_pts
546 || p_synchro->current_pts - next_dts
547 > PTS_THRESHOLD) && !p_synchro->b_quiet )
549 msg_Warn( p_synchro->p_dec, "dts != current_pts (%"PRId64")",
550 p_synchro->current_pts
553 /* By definition of a DTS. */
554 p_synchro->current_pts = next_dts;
560 /* Store the PTS for the next time we have to date an I picture. */
561 p_synchro->backward_pts = next_pts;
568 /* Removed for incompatibility with slow motion */
569 if( p_synchro->current_pts + DEFAULT_PTS_DELAY < now )
571 /* We cannot be _that_ late, something must have happened, reinit
573 if( !p_synchro->b_quiet )
574 msg_Warn( p_synchro->p_dec, "PTS << now (%"PRId64"), resetting",
575 now - p_synchro->current_pts - DEFAULT_PTS_DELAY );
576 p_synchro->current_pts = now + DEFAULT_PTS_DELAY;
578 if( p_synchro->backward_pts
579 && p_synchro->backward_pts + DEFAULT_PTS_DELAY < now )
582 p_synchro->backward_pts = 0;