* String review, round one
[vlc.git] / src / video_output / vout_synchro.c
1 /*****************************************************************************
2  * vout_synchro.c : frame dropping routines
3  *****************************************************************************
4  * Copyright (C) 1999-2004 VideoLAN
5  * $Id: vout_synchro.c,v 1.7 2004/01/25 17:16:06 zorglub Exp $
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., 59 Temple Place - Suite 330, Boston, MA  02111, 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 <stdlib.h>                                                /* free() */
98 #include <string.h>                                    /* memcpy(), memset() */
99
100 #include <vlc/vlc.h>
101 #include <vlc/vout.h>
102
103 #include "vout_synchro.h"
104 #include "stream_control.h"
105
106 /*
107  * Local prototypes
108  */
109
110 /* Error margins */
111 #define DELTA                   (int)(0.075*CLOCK_FREQ)
112 #define MAX_VALID_TAU           (int)(0.3*CLOCK_FREQ)
113
114 #define DEFAULT_NB_P            5
115 #define DEFAULT_NB_B            1
116
117 /*****************************************************************************
118  * vout_SynchroInit : You know what ?
119  *****************************************************************************/
120 vout_synchro_t * __vout_SynchroInit( vlc_object_t * p_object,
121                                      int i_frame_rate )
122 {
123     vout_synchro_t * p_synchro = vlc_object_create( p_object,
124                                                   sizeof(vout_synchro_t) );
125     if ( p_synchro == NULL )
126     {
127         msg_Err( p_object, "out of memory" );
128         return NULL;
129     }
130     vlc_object_attach( p_synchro, p_object );
131
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;
144
145     p_synchro->i_frame_rate = i_frame_rate;
146
147     return p_synchro;
148 }
149
150 /*****************************************************************************
151  * vout_SynchroRelease : You know what ?
152  *****************************************************************************/
153 void vout_SynchroRelease( vout_synchro_t * p_synchro )
154 {
155     vlc_object_detach( p_synchro );
156     vlc_object_destroy( p_synchro );
157 }
158
159 /*****************************************************************************
160  * vout_SynchroReset : Reset the reference picture counter
161  *****************************************************************************/
162 void vout_SynchroReset( vout_synchro_t * p_synchro )
163 {
164     p_synchro->i_nb_ref = 0;
165     p_synchro->i_trash_nb_ref = p_synchro->i_dec_nb_ref = 0;
166 }
167
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,
172                                int i_render_time )
173 {
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 */
179     mtime_t         now, period;
180     mtime_t         pts = 0;
181     vlc_bool_t      b_decode = 0;
182
183     now = mdate();
184     period = 1000000 * 1001 / p_synchro->i_frame_rate
185                      * p_synchro->i_current_rate / DEFAULT_RATE;
186
187     p_synchro->i_render_time = i_render_time;
188
189     switch( i_coding_type )
190     {
191     case I_CODING_TYPE:
192         if( S.backward_pts )
193         {
194             pts = S.backward_pts;
195         }
196         else
197         {
198             /* displaying order : B B P B B I
199              *                      ^       ^
200              *                      |       +- current picture
201              *                      +- current PTS
202              */
203             pts = S.current_pts + period * (S.i_n_b + 2);
204         }
205
206         if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
207                 S.p_tau[I_CODING_TYPE] )
208         {
209             b_decode = 1;
210         }
211         else
212         {
213             b_decode = (pts - now) > (TAU_PRIME(I_CODING_TYPE) + DELTA);
214         }
215         if( !b_decode )
216         {
217             msg_Warn( p_synchro,
218                       "synchro trashing I ("I64Fd")", pts - now );
219         }
220         break;
221
222     case P_CODING_TYPE:
223         if( S.backward_pts )
224         {
225             pts = S.backward_pts;
226         }
227         else
228         {
229             pts = S.current_pts + period * (S.i_n_b + 1);
230         }
231
232         if( p_synchro->i_nb_ref < 1 )
233         {
234             b_decode = 0;
235         }
236         else if( (1 + S.i_n_p * (S.i_n_b + 1)) * period >
237                 S.p_tau[I_CODING_TYPE] )
238         {
239             if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
240             {
241                 /* Security in case we're _really_ late */
242                 b_decode = (pts - now > 0);
243             }
244             else
245             {
246                 b_decode = (pts - now) > (TAU_PRIME(P_CODING_TYPE) + DELTA);
247                 /* next I */
248                 b_decode &= (pts - now
249                               + period
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);
253             }
254         }
255         else
256         {
257             b_decode = 0;
258         }
259         break;
260
261     case B_CODING_TYPE:
262         pts = S.current_pts;
263
264         if( p_synchro->i_nb_ref < 2 )
265         {
266             b_decode = 0;
267         }
268         else if( (S.i_n_b + 1) * period > S.p_tau[P_CODING_TYPE] )
269         {
270             b_decode = (pts - now) > (TAU_PRIME(B_CODING_TYPE) + DELTA);
271         }
272         else
273         {
274             b_decode = 0;
275         }
276     }
277
278     if( !b_decode )
279     {
280         S.i_not_chosen_pic++;
281     }
282     return( b_decode );
283 #undef S
284 #undef TAU_PRIME
285 }
286
287 /*****************************************************************************
288  * vout_SynchroTrash : Update counters when we trash a picture
289  *****************************************************************************/
290 void vout_SynchroTrash( vout_synchro_t * p_synchro )
291 {
292     p_synchro->i_trashed_pic++;
293     p_synchro->i_nb_ref = p_synchro->i_trash_nb_ref;
294 }
295
296 /*****************************************************************************
297  * vout_SynchroDecode : Update timers when we decide to decode a picture
298  *****************************************************************************/
299 void vout_SynchroDecode( vout_synchro_t * p_synchro )
300 {
301     p_synchro->decoding_start = mdate();
302     p_synchro->i_nb_ref = p_synchro->i_dec_nb_ref;
303 }
304
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 )
310 {
311     mtime_t     tau;
312
313     if( !b_garbage )
314     {
315         tau = mdate() - p_synchro->decoding_start;
316
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 ) )
322         {
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 )
329             {
330                 p_synchro->pi_meaningful[i_coding_type]++;
331             }
332         }
333     }
334 }
335
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 )
340 {
341     /* No need to lock, since PTS are only used by the video parser. */
342     return p_synchro->current_pts;
343 }
344
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 )
351 {
352     mtime_t         period = 1000000 * 1001 / p_synchro->i_frame_rate
353                               * i_current_rate / DEFAULT_RATE;
354 #if 0
355     mtime_t         now = mdate();
356 #endif
357     p_synchro->i_current_rate = i_current_rate;
358
359     switch( i_coding_type )
360     {
361     case I_CODING_TYPE:
362         if( p_synchro->i_eta_p
363              && p_synchro->i_eta_p != p_synchro->i_n_p )
364         {
365             msg_Dbg( p_synchro,
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;
369         }
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;
374         else
375             p_synchro->i_dec_nb_ref = p_synchro->i_nb_ref;
376
377 #if 0
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],
382               p_synchro->i_n_p,
383               p_synchro->p_tau[B_CODING_TYPE],
384               p_synchro->i_n_b,
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,
389               p_synchro->i_pic );
390         p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
391             = p_synchro->i_pic = 0;
392 #else
393         if ( p_synchro->i_pic >= 100 )
394         {
395             msg_Dbg( p_synchro, "decoded %d/%d pictures",
396                      p_synchro->i_pic
397                        - p_synchro->i_trashed_pic,
398                      p_synchro->i_pic );
399             p_synchro->i_trashed_pic = p_synchro->i_not_chosen_pic
400                 = p_synchro->i_pic = 0;
401         }
402 #endif
403         break;
404
405     case P_CODING_TYPE:
406         p_synchro->i_eta_p++;
407         if( p_synchro->i_eta_b
408              && p_synchro->i_eta_b != p_synchro->i_n_b )
409         {
410             msg_Dbg( p_synchro,
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;
414         }
415         p_synchro->i_eta_b = 0;
416         p_synchro->i_dec_nb_ref = 2;
417         p_synchro->i_trash_nb_ref = 0;
418         break;
419
420     case B_CODING_TYPE:
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;
424         break;
425     }
426
427     p_synchro->current_pts += p_synchro->i_current_period
428                                         * (period >> 1);
429
430 #define PTS_THRESHOLD   (period >> 2)
431     if( i_coding_type == B_CODING_TYPE )
432     {
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;
437
438         if( next_pts )
439         {
440             if( next_pts - p_synchro->current_pts
441                     > PTS_THRESHOLD
442                  || p_synchro->current_pts - next_pts
443                     > PTS_THRESHOLD )
444             {
445                 msg_Warn( p_synchro, "vout synchro warning: pts != "
446                           "current_date ("I64Fd")",
447                           p_synchro->current_pts
448                               - next_pts );
449             }
450             p_synchro->current_pts = next_pts;
451         }
452     }
453     else
454     {
455         p_synchro->i_current_period = p_synchro->i_backward_period;
456         p_synchro->i_backward_period = i_repeat_field;
457
458         if( p_synchro->backward_pts )
459         {
460             if( next_dts &&
461                 (next_dts - p_synchro->backward_pts
462                     > PTS_THRESHOLD
463               || p_synchro->backward_pts - next_dts
464                     > PTS_THRESHOLD) )
465             {
466                 msg_Warn( p_synchro, "backward_pts != dts ("I64Fd")",
467                            next_dts
468                                - p_synchro->backward_pts );
469             }
470             if( p_synchro->backward_pts - p_synchro->current_pts
471                     > PTS_THRESHOLD
472                  || p_synchro->current_pts - p_synchro->backward_pts
473                     > PTS_THRESHOLD )
474             {
475                 msg_Warn( p_synchro,
476                           "backward_pts != current_pts ("I64Fd")",
477                           p_synchro->current_pts
478                               - p_synchro->backward_pts );
479             }
480             p_synchro->current_pts = p_synchro->backward_pts;
481             p_synchro->backward_pts = 0;
482         }
483         else if( next_dts )
484         {
485             if( next_dts - p_synchro->current_pts
486                     > PTS_THRESHOLD
487                  || p_synchro->current_pts - next_dts
488                     > PTS_THRESHOLD )
489             {
490                 msg_Warn( p_synchro, "dts != current_pts ("I64Fd")",
491                           p_synchro->current_pts
492                               - next_dts );
493             }
494             /* By definition of a DTS. */
495             p_synchro->current_pts = next_dts;
496             next_dts = 0;
497         }
498
499         if( next_pts )
500         {
501             /* Store the PTS for the next time we have to date an I picture. */
502             p_synchro->backward_pts = next_pts;
503             next_pts = 0;
504         }
505     }
506 #undef PTS_THRESHOLD
507
508 #if 0
509     /* Removed for incompatibility with slow motion */
510     if( p_synchro->current_pts + DEFAULT_PTS_DELAY < now )
511     {
512         /* We cannot be _that_ late, something must have happened, reinit
513          * the dates. */
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;
517     }
518     if( p_synchro->backward_pts
519          && p_synchro->backward_pts + DEFAULT_PTS_DELAY < now )
520     {
521         /* The same. */
522         p_synchro->backward_pts = 0;
523     }
524 #endif
525
526     p_synchro->i_pic++;
527 }