1 /*****************************************************************************
2 * vpar_synchro.c : frame dropping routines
3 *****************************************************************************
4 * Copyright (C) 1999-2001 VideoLAN
5 * $Id: synchro.c,v 1.2 2002/08/04 18:39:41 sam Exp $
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., 59 Temple Place - Suite 330, Boston, MA 02111, 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 *****************************************************************************/
97 #include <stdlib.h> /* free() */
98 #include <string.h> /* memcpy(), memset() */
101 #include <vlc/vout.h>
102 #include <vlc/decoder.h>
112 static int SynchroType( decoder_fifo_t * );
115 #define DELTA (int)(0.075*CLOCK_FREQ)
117 #define DEFAULT_NB_P 5
118 #define DEFAULT_NB_B 1
120 /*****************************************************************************
121 * vpar_SynchroInit : You know what ?
122 *****************************************************************************/
123 void vpar_SynchroInit( vpar_thread_t * p_vpar )
125 p_vpar->synchro.i_type = SynchroType( p_vpar->p_fifo );
127 /* We use a fake stream pattern, which is often right. */
128 p_vpar->synchro.i_n_p = p_vpar->synchro.i_eta_p = DEFAULT_NB_P;
129 p_vpar->synchro.i_n_b = p_vpar->synchro.i_eta_b = DEFAULT_NB_B;
130 memset( p_vpar->synchro.p_tau, 0, 4 * sizeof(mtime_t) );
131 memset( p_vpar->synchro.pi_meaningful, 0, 4 * sizeof(unsigned int) );
132 p_vpar->synchro.b_dropped_last = 0;
133 p_vpar->synchro.current_pts = mdate() + DEFAULT_PTS_DELAY;
134 p_vpar->synchro.backward_pts = 0;
135 p_vpar->synchro.i_current_period = p_vpar->synchro.i_backward_period = 0;
136 p_vpar->synchro.i_trashed_pic = p_vpar->synchro.i_not_chosen_pic =
137 p_vpar->synchro.i_pic = 0;
140 /*****************************************************************************
141 * vpar_SynchroChoose : Decide whether we will decode a picture or not
142 *****************************************************************************/
143 vlc_bool_t vpar_SynchroChoose( vpar_thread_t * p_vpar, int i_coding_type,
146 /* For clarity reasons, we separated the special synchros code from the
147 * mathematical synchro */
149 if( p_vpar->synchro.i_type != VPAR_SYNCHRO_DEFAULT )
151 switch( i_coding_type )
154 /* I, IP, IP+, IPB */
155 if( p_vpar->synchro.i_type == VPAR_SYNCHRO_Iplus )
157 p_vpar->synchro.b_dropped_last = 1;
162 if( p_vpar->synchro.i_type == VPAR_SYNCHRO_I ) /* I */
167 if( p_vpar->synchro.i_type == VPAR_SYNCHRO_Iplus ) /* I+ */
169 if( p_vpar->synchro.b_dropped_last )
171 p_vpar->synchro.b_dropped_last = 0;
180 return( 1 ); /* IP, IP+, IPB */
183 if( p_vpar->synchro.i_type <= VPAR_SYNCHRO_IP ) /* I, IP */
187 else if( p_vpar->synchro.i_type == VPAR_SYNCHRO_IPB ) /* IPB */
192 p_vpar->synchro.b_dropped_last ^= 1; /* IP+ */
193 return( !p_vpar->synchro.b_dropped_last );
195 return( 0 ); /* never reached but gcc yells at me */
199 #define TAU_PRIME( coding_type ) (p_vpar->synchro.p_tau[(coding_type)] \
200 + (p_vpar->synchro.p_tau[(coding_type)] >> 1) \
202 #define S p_vpar->synchro
203 /* VPAR_SYNCHRO_DEFAULT */
204 mtime_t now, period, tau_yuv;
206 vlc_bool_t b_decode = 0;
209 period = 1000000 * 1001 / p_vpar->sequence.i_frame_rate
210 * p_vpar->sequence.i_current_rate / DEFAULT_RATE;
212 vlc_mutex_lock( &p_vpar->p_vout->change_lock );
213 tau_yuv = p_vpar->p_vout->render_time;
214 vlc_mutex_unlock( &p_vpar->p_vout->change_lock );
216 switch( i_coding_type )
221 pts = S.backward_pts;
225 /* displaying order : B B P B B I
227 * | +- current picture
230 pts = S.current_pts + period * (S.i_n_b + 2);
233 if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
234 S.p_tau[I_CODING_TYPE] )
240 b_decode = (pts - now) > (TAU_PRIME(I_CODING_TYPE) + DELTA);
243 msg_Warn( p_vpar->p_fifo,
244 "synchro trashing I (%lld)", pts - now );
250 pts = S.backward_pts;
254 pts = S.current_pts + period * (S.i_n_b + 1);
257 if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
258 S.p_tau[I_CODING_TYPE] )
260 if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
262 /* Security in case we're _really_ late */
263 b_decode = (pts - now > 0);
267 b_decode = (pts - now) > (TAU_PRIME(P_CODING_TYPE) + DELTA);
269 b_decode &= (pts - now
271 * ( (S.i_n_p - S.i_eta_p) * (1 + S.i_n_b) - 1 ))
272 > (TAU_PRIME(P_CODING_TYPE)
273 + TAU_PRIME(I_CODING_TYPE) + DELTA);
285 if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
287 b_decode = (pts - now) > (TAU_PRIME(B_CODING_TYPE) + DELTA);
297 S.i_not_chosen_pic++;
305 /*****************************************************************************
306 * vpar_SynchroTrash : Update counters when we trash a picture
307 *****************************************************************************/
308 void vpar_SynchroTrash( vpar_thread_t * p_vpar, int i_coding_type,
311 p_vpar->synchro.i_trashed_pic++;
314 /*****************************************************************************
315 * vpar_SynchroDecode : Update timers when we decide to decode a picture
316 *****************************************************************************/
317 void vpar_SynchroDecode( vpar_thread_t * p_vpar, int i_coding_type,
320 p_vpar->synchro.decoding_start = mdate();
323 /*****************************************************************************
324 * vpar_SynchroEnd : Called when the image is totally decoded
325 *****************************************************************************/
326 void vpar_SynchroEnd( vpar_thread_t * p_vpar, int i_coding_type,
327 int i_structure, int i_garbage )
333 tau = mdate() - p_vpar->synchro.decoding_start;
335 /* If duration too high, something happened (pause ?), so don't
336 * take it into account. */
337 if( tau < 3 * p_vpar->synchro.p_tau[i_coding_type]
338 || !p_vpar->synchro.pi_meaningful[i_coding_type] )
340 /* Mean with average tau, to ensure stability. */
341 p_vpar->synchro.p_tau[i_coding_type] =
342 (p_vpar->synchro.pi_meaningful[i_coding_type]
343 * p_vpar->synchro.p_tau[i_coding_type] + tau)
344 / (p_vpar->synchro.pi_meaningful[i_coding_type] + 1);
345 if( p_vpar->synchro.pi_meaningful[i_coding_type] < MAX_PIC_AVERAGE )
347 p_vpar->synchro.pi_meaningful[i_coding_type]++;
353 /*****************************************************************************
354 * vpar_SynchroDate : When an image has been decoded, ask for its date
355 *****************************************************************************/
356 mtime_t vpar_SynchroDate( vpar_thread_t * p_vpar )
358 /* No need to lock, since PTS are only used by the video parser. */
359 return( p_vpar->synchro.current_pts );
362 /*****************************************************************************
363 * vpar_SynchroNewPicture: Update stream structure and PTS
364 *****************************************************************************/
365 void vpar_SynchroNewPicture( vpar_thread_t * p_vpar, int i_coding_type,
368 mtime_t period = 1000000 * 1001 / p_vpar->sequence.i_frame_rate
369 * p_vpar->sequence.i_current_rate / DEFAULT_RATE;
371 mtime_t now = mdate();
374 switch( i_coding_type )
377 if( p_vpar->synchro.i_eta_p
378 && p_vpar->synchro.i_eta_p != p_vpar->synchro.i_n_p )
380 msg_Warn( p_vpar->p_fifo,
381 "stream periodicity changed from P[%d] to P[%d]",
382 p_vpar->synchro.i_n_p, p_vpar->synchro.i_eta_p );
383 p_vpar->synchro.i_n_p = p_vpar->synchro.i_eta_p;
385 p_vpar->synchro.i_eta_p = p_vpar->synchro.i_eta_b = 0;
387 if( p_vpar->synchro.i_type == VPAR_SYNCHRO_DEFAULT )
389 msg_Dbg( p_vpar->p_fifo, "I(%lld) P(%lld)[%d] B(%lld)[%d] YUV(%lld) : trashed %d:%d/%d",
390 p_vpar->synchro.p_tau[I_CODING_TYPE],
391 p_vpar->synchro.p_tau[P_CODING_TYPE],
392 p_vpar->synchro.i_n_p,
393 p_vpar->synchro.p_tau[B_CODING_TYPE],
394 p_vpar->synchro.i_n_b,
395 p_vpar->p_vout->render_time,
396 p_vpar->synchro.i_not_chosen_pic,
397 p_vpar->synchro.i_trashed_pic -
398 p_vpar->synchro.i_not_chosen_pic,
399 p_vpar->synchro.i_pic );
400 p_vpar->synchro.i_trashed_pic = p_vpar->synchro.i_not_chosen_pic
401 = p_vpar->synchro.i_pic = 0;
406 p_vpar->synchro.i_eta_p++;
407 if( p_vpar->synchro.i_eta_b
408 && p_vpar->synchro.i_eta_b != p_vpar->synchro.i_n_b )
410 msg_Warn( p_vpar->p_fifo,
411 "stream periodicity changed from B[%d] to B[%d]",
412 p_vpar->synchro.i_n_b, p_vpar->synchro.i_eta_b );
413 p_vpar->synchro.i_n_b = p_vpar->synchro.i_eta_b;
415 p_vpar->synchro.i_eta_b = 0;
418 p_vpar->synchro.i_eta_b++;
422 p_vpar->synchro.current_pts += p_vpar->synchro.i_current_period
425 #define PTS_THRESHOLD (period >> 2)
426 if( i_coding_type == B_CODING_TYPE )
428 /* A video frame can be displayed 1, 2 or 3 times, according to
429 * repeat_first_field, top_field_first, progressive_sequence and
430 * progressive_frame. */
431 p_vpar->synchro.i_current_period = i_repeat_field;
433 if( p_vpar->sequence.next_pts )
435 if( p_vpar->sequence.next_pts - p_vpar->synchro.current_pts
437 || p_vpar->synchro.current_pts - p_vpar->sequence.next_pts
440 msg_Warn( p_vpar->p_fifo,
441 "vpar synchro warning: pts != current_date (%lld)",
442 p_vpar->synchro.current_pts
443 - p_vpar->sequence.next_pts );
445 p_vpar->synchro.current_pts = p_vpar->sequence.next_pts;
446 p_vpar->sequence.next_pts = 0;
451 p_vpar->synchro.i_current_period = p_vpar->synchro.i_backward_period;
452 p_vpar->synchro.i_backward_period = i_repeat_field;
454 if( p_vpar->synchro.backward_pts )
456 if( p_vpar->sequence.next_dts &&
457 (p_vpar->sequence.next_dts - p_vpar->synchro.backward_pts
459 || p_vpar->synchro.backward_pts - p_vpar->sequence.next_dts
462 msg_Warn( p_vpar->p_fifo, "backward_pts != dts (%lld)",
463 p_vpar->sequence.next_dts
464 - p_vpar->synchro.backward_pts );
466 if( p_vpar->synchro.backward_pts - p_vpar->synchro.current_pts
468 || p_vpar->synchro.current_pts - p_vpar->synchro.backward_pts
471 msg_Warn( p_vpar->p_fifo,
472 "backward_pts != current_pts (%lld)",
473 p_vpar->synchro.current_pts
474 - p_vpar->synchro.backward_pts );
476 p_vpar->synchro.current_pts = p_vpar->synchro.backward_pts;
477 p_vpar->synchro.backward_pts = 0;
479 else if( p_vpar->sequence.next_dts )
481 if( p_vpar->sequence.next_dts - p_vpar->synchro.current_pts
483 || p_vpar->synchro.current_pts - p_vpar->sequence.next_dts
486 msg_Warn( p_vpar->p_fifo, "dts != current_pts (%lld)",
487 p_vpar->synchro.current_pts
488 - p_vpar->sequence.next_dts );
490 /* By definition of a DTS. */
491 p_vpar->synchro.current_pts = p_vpar->sequence.next_dts;
492 p_vpar->sequence.next_dts = 0;
495 if( p_vpar->sequence.next_pts )
497 /* Store the PTS for the next time we have to date an I picture. */
498 p_vpar->synchro.backward_pts = p_vpar->sequence.next_pts;
499 p_vpar->sequence.next_pts = 0;
505 /* Removed for incompatibility with slow motion */
506 if( p_vpar->synchro.current_pts + DEFAULT_PTS_DELAY < now )
508 /* We cannot be _that_ late, something must have happened, reinit
510 msg_Warn( p_vpar->p_fifo, "PTS << now (%lld), resetting",
511 now - p_vpar->synchro.current_pts - DEFAULT_PTS_DELAY );
512 p_vpar->synchro.current_pts = now + DEFAULT_PTS_DELAY;
514 if( p_vpar->synchro.backward_pts
515 && p_vpar->synchro.backward_pts + DEFAULT_PTS_DELAY < now )
518 p_vpar->synchro.backward_pts = 0;
522 p_vpar->synchro.i_pic++;
525 /*****************************************************************************
526 * SynchroType: Get the user's synchro type
527 *****************************************************************************
528 * This function is called at initialization.
529 *****************************************************************************/
530 static int SynchroType( decoder_fifo_t *p_this )
532 char psz_synchro_tmp[5];
533 char * psz_synchro = config_GetPsz( p_this, "vpar-synchro" );
535 if( psz_synchro == NULL )
537 return VPAR_SYNCHRO_DEFAULT;
540 strncpy( psz_synchro_tmp, psz_synchro, 5);
542 psz_synchro = psz_synchro_tmp;
544 switch( *psz_synchro++ )
548 switch( *psz_synchro++ )
551 return VPAR_SYNCHRO_I;
554 if( *psz_synchro ) return 0;
555 return VPAR_SYNCHRO_Iplus;
559 switch( *psz_synchro++ )
562 return VPAR_SYNCHRO_IP;
565 if( *psz_synchro ) return 0;
566 return VPAR_SYNCHRO_IPplus;
570 if( *psz_synchro ) return 0;
571 return VPAR_SYNCHRO_IPB;
574 return VPAR_SYNCHRO_DEFAULT;
579 return VPAR_SYNCHRO_DEFAULT;
583 return VPAR_SYNCHRO_DEFAULT;