1 /*****************************************************************************
2 * vout_synchro.c : frame dropping routines
3 *****************************************************************************
4 * Copyright (C) 1999-2001 VideoLAN
5 * $Id: vout_synchro.c,v 1.5 2003/11/04 17:46:18 gbazin 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>
103 #include "vout_synchro.h"
104 #include "stream_control.h"
111 #define DELTA (int)(0.075*CLOCK_FREQ)
112 #define MAX_VALID_TAU (int)(0.3*CLOCK_FREQ)
114 #define DEFAULT_NB_P 5
115 #define DEFAULT_NB_B 1
117 /*****************************************************************************
118 * vout_SynchroInit : You know what ?
119 *****************************************************************************/
120 vout_synchro_t * __vout_SynchroInit( vlc_object_t * p_object,
123 vout_synchro_t * p_synchro = vlc_object_create( p_object,
124 sizeof(vout_synchro_t) );
125 if ( p_synchro == NULL )
127 msg_Err( p_object, "out of memory" );
130 vlc_object_attach( p_synchro, p_object );
132 /* We use a fake stream pattern, which is often right. */
133 p_synchro->i_n_p = p_synchro->i_eta_p = DEFAULT_NB_P;
134 p_synchro->i_n_b = p_synchro->i_eta_b = DEFAULT_NB_B;
135 memset( p_synchro->p_tau, 0, 4 * sizeof(mtime_t) );
136 memset( p_synchro->pi_meaningful, 0, 4 * sizeof(unsigned int) );
137 p_synchro->i_nb_ref = 0;
138 p_synchro->i_trash_nb_ref = p_synchro->i_dec_nb_ref = 0;
139 p_synchro->current_pts = mdate() + DEFAULT_PTS_DELAY;
140 p_synchro->backward_pts = 0;
141 p_synchro->i_current_period = p_synchro->i_backward_period = 0;
142 p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic =
143 p_synchro->i_pic = 0;
145 p_synchro->i_frame_rate = i_frame_rate;
150 /*****************************************************************************
151 * vout_SynchroRelease : You know what ?
152 *****************************************************************************/
153 void vout_SynchroRelease( vout_synchro_t * p_synchro )
155 vlc_object_detach( p_synchro );
156 vlc_object_destroy( p_synchro );
159 /*****************************************************************************
160 * vout_SynchroReset : Reset the reference picture counter
161 *****************************************************************************/
162 void vout_SynchroReset( vout_synchro_t * p_synchro )
164 p_synchro->i_nb_ref = 0;
165 p_synchro->i_trash_nb_ref = p_synchro->i_dec_nb_ref = 0;
168 /*****************************************************************************
169 * vout_SynchroChoose : Decide whether we will decode a picture or not
170 *****************************************************************************/
171 vlc_bool_t vout_SynchroChoose( vout_synchro_t * p_synchro, int i_coding_type,
174 #define TAU_PRIME( coding_type ) (p_synchro->p_tau[(coding_type)] \
175 + (p_synchro->p_tau[(coding_type)] >> 1) \
176 + p_synchro->i_render_time)
177 #define S (*p_synchro)
178 /* VPAR_SYNCHRO_DEFAULT */
181 vlc_bool_t b_decode = 0;
184 period = 1000000 * 1001 / p_synchro->i_frame_rate
185 * p_synchro->i_current_rate / DEFAULT_RATE;
187 p_synchro->i_render_time = i_render_time;
189 switch( i_coding_type )
194 pts = S.backward_pts;
198 /* displaying order : B B P B B I
200 * | +- current picture
203 pts = S.current_pts + period * (S.i_n_b + 2);
206 if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
207 S.p_tau[I_CODING_TYPE] )
213 b_decode = (pts - now) > (TAU_PRIME(I_CODING_TYPE) + DELTA);
218 "synchro trashing I ("I64Fd")", pts - now );
225 pts = S.backward_pts;
229 pts = S.current_pts + period * (S.i_n_b + 1);
232 if( p_synchro->i_nb_ref < 1 )
236 else if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
237 S.p_tau[I_CODING_TYPE] )
239 if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
241 /* Security in case we're _really_ late */
242 b_decode = (pts - now > 0);
246 b_decode = (pts - now) > (TAU_PRIME(P_CODING_TYPE) + DELTA);
248 b_decode &= (pts - now
250 * ( (S.i_n_p - S.i_eta_p) * (1 + S.i_n_b) - 1 ))
251 > (TAU_PRIME(P_CODING_TYPE)
252 + TAU_PRIME(I_CODING_TYPE) + DELTA);
264 if( p_synchro->i_nb_ref < 2 )
268 else if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
270 b_decode = (pts - now) > (TAU_PRIME(B_CODING_TYPE) + DELTA);
280 S.i_not_chosen_pic++;
287 /*****************************************************************************
288 * vout_SynchroTrash : Update counters when we trash a picture
289 *****************************************************************************/
290 void vout_SynchroTrash( vout_synchro_t * p_synchro )
292 p_synchro->i_trashed_pic++;
293 p_synchro->i_nb_ref = p_synchro->i_trash_nb_ref;
296 /*****************************************************************************
297 * vout_SynchroDecode : Update timers when we decide to decode a picture
298 *****************************************************************************/
299 void vout_SynchroDecode( vout_synchro_t * p_synchro )
301 p_synchro->decoding_start = mdate();
302 p_synchro->i_nb_ref = p_synchro->i_dec_nb_ref;
305 /*****************************************************************************
306 * vout_SynchroEnd : Called when the image is totally decoded
307 *****************************************************************************/
308 void vout_SynchroEnd( vout_synchro_t * p_synchro, int i_coding_type,
309 vlc_bool_t b_garbage )
315 tau = mdate() - p_synchro->decoding_start;
317 /* If duration too high, something happened (pause ?), so don't
318 * take it into account. */
319 if( tau < 3 * p_synchro->p_tau[i_coding_type]
320 || ( !p_synchro->pi_meaningful[i_coding_type]
321 && tau < MAX_VALID_TAU ) )
323 /* Mean with average tau, to ensure stability. */
324 p_synchro->p_tau[i_coding_type] =
325 (p_synchro->pi_meaningful[i_coding_type]
326 * p_synchro->p_tau[i_coding_type] + tau)
327 / (p_synchro->pi_meaningful[i_coding_type] + 1);
328 if( p_synchro->pi_meaningful[i_coding_type] < MAX_PIC_AVERAGE )
330 p_synchro->pi_meaningful[i_coding_type]++;
336 /*****************************************************************************
337 * vout_SynchroDate : When an image has been decoded, ask for its date
338 *****************************************************************************/
339 mtime_t vout_SynchroDate( vout_synchro_t * p_synchro )
341 /* No need to lock, since PTS are only used by the video parser. */
342 return p_synchro->current_pts;
345 /*****************************************************************************
346 * vout_SynchroNewPicture: Update stream structure and PTS
347 *****************************************************************************/
348 void vout_SynchroNewPicture( vout_synchro_t * p_synchro, int i_coding_type,
349 int i_repeat_field, mtime_t next_pts,
350 mtime_t next_dts, int i_current_rate )
352 mtime_t period = 1000000 * 1001 / p_synchro->i_frame_rate
353 * i_current_rate / DEFAULT_RATE;
355 mtime_t now = mdate();
357 p_synchro->i_current_rate = i_current_rate;
359 switch( i_coding_type )
362 if( p_synchro->i_eta_p
363 && p_synchro->i_eta_p != p_synchro->i_n_p )
366 "stream periodicity changed from P[%d] to P[%d]",
367 p_synchro->i_n_p, p_synchro->i_eta_p );
368 p_synchro->i_n_p = p_synchro->i_eta_p;
370 p_synchro->i_eta_p = p_synchro->i_eta_b = 0;
371 p_synchro->i_trash_nb_ref = 0;
372 if( p_synchro->i_nb_ref < 2 )
373 p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref + 1;
375 p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref;
378 msg_Dbg( p_synchro, "I("I64Fd") P("I64Fd")[%d] B("I64Fd")"
379 "[%d] YUV("I64Fd") : trashed %d:%d/%d",
380 p_synchro->p_tau[I_CODING_TYPE],
381 p_synchro->p_tau[P_CODING_TYPE],
383 p_synchro->p_tau[B_CODING_TYPE],
385 p_synchro->i_render_time,
386 p_synchro->i_not_chosen_pic,
387 p_synchro->i_trashed_pic -
388 p_synchro->i_not_chosen_pic,
390 p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
391 = p_synchro->i_pic = 0;
393 if ( p_synchro->i_pic >= 100 )
395 msg_Dbg( p_synchro, "decoded %d/%d pictures",
397 - p_synchro->i_trashed_pic,
399 p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
400 = p_synchro->i_pic = 0;
406 p_synchro->i_eta_p++;
407 if( p_synchro->i_eta_b
408 && p_synchro->i_eta_b != p_synchro->i_n_b )
411 "stream periodicity changed from B[%d] to B[%d]",
412 p_synchro->i_n_b, p_synchro->i_eta_b );
413 p_synchro->i_n_b = p_synchro->i_eta_b;
415 p_synchro->i_eta_b = 0;
416 p_synchro->i_dec_nb_ref = 2;
417 p_synchro->i_trash_nb_ref = 0;
421 p_synchro->i_eta_b++;
422 p_synchro->i_dec_nb_ref = p_synchro->i_trash_nb_ref
423 = p_synchro->i_nb_ref;
427 p_synchro->current_pts += p_synchro->i_current_period
430 #define PTS_THRESHOLD (period >> 2)
431 if( i_coding_type == B_CODING_TYPE )
433 /* A video frame can be displayed 1, 2 or 3 times, according to
434 * repeat_first_field, top_field_first, progressive_sequence and
435 * progressive_frame. */
436 p_synchro->i_current_period = i_repeat_field;
440 if( next_pts - p_synchro->current_pts
442 || p_synchro->current_pts - next_pts
445 msg_Warn( p_synchro, "vout synchro warning: pts != "
446 "current_date ("I64Fd")",
447 p_synchro->current_pts
450 p_synchro->current_pts = next_pts;
455 p_synchro->i_current_period = p_synchro->i_backward_period;
456 p_synchro->i_backward_period = i_repeat_field;
458 if( p_synchro->backward_pts )
461 (next_dts - p_synchro->backward_pts
463 || p_synchro->backward_pts - next_dts
466 msg_Warn( p_synchro, "backward_pts != dts ("I64Fd")",
468 - p_synchro->backward_pts );
470 if( p_synchro->backward_pts - p_synchro->current_pts
472 || p_synchro->current_pts - p_synchro->backward_pts
476 "backward_pts != current_pts ("I64Fd")",
477 p_synchro->current_pts
478 - p_synchro->backward_pts );
480 p_synchro->current_pts = p_synchro->backward_pts;
481 p_synchro->backward_pts = 0;
485 if( next_dts - p_synchro->current_pts
487 || p_synchro->current_pts - next_dts
490 msg_Warn( p_synchro, "dts != current_pts ("I64Fd")",
491 p_synchro->current_pts
494 /* By definition of a DTS. */
495 p_synchro->current_pts = next_dts;
501 /* Store the PTS for the next time we have to date an I picture. */
502 p_synchro->backward_pts = next_pts;
509 /* Removed for incompatibility with slow motion */
510 if( p_synchro->current_pts + DEFAULT_PTS_DELAY < now )
512 /* We cannot be _that_ late, something must have happened, reinit
514 msg_Warn( p_synchro, "PTS << now ("I64Fd"), resetting",
515 now - p_synchro->current_pts - DEFAULT_PTS_DELAY );
516 p_synchro->current_pts = now + DEFAULT_PTS_DELAY;
518 if( p_synchro->backward_pts
519 && p_synchro->backward_pts + DEFAULT_PTS_DELAY < now )
522 p_synchro->backward_pts = 0;