1 /*****************************************************************************
2 * clock.c: Clock/System date convertions, stream management
3 *****************************************************************************
4 * Copyright (C) 1999-2008 the VideoLAN team
5 * Copyright (C) 2008 Laurent Aimar
8 * Authors: Christophe Massiot <massiot@via.ecp.fr>
9 * Laurent Aimar < fenrir _AT_ videolan _DOT_ org >
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 *****************************************************************************/
26 /*****************************************************************************
28 *****************************************************************************/
33 #include <vlc_common.h>
34 #include <vlc_input.h>
39 * - clean up locking once clock code is stable
44 * DISCUSSION : SYNCHRONIZATION METHOD
46 * In some cases we can impose the pace of reading (when reading from a
47 * file or a pipe), and for the synchronization we simply sleep() until
48 * it is time to deliver the packet to the decoders. When reading from
49 * the network, we must be read at the same pace as the server writes,
50 * otherwise the kernel's buffer will trash packets. The risk is now to
51 * overflow the input buffers in case the server goes too fast, that is
52 * why we do these calculations :
54 * We compute a mean for the pcr because we want to eliminate the
55 * network jitter and keep the low frequency variations. The mean is
56 * in fact a low pass filter and the jitter is a high frequency signal
57 * that is why it is eliminated by the filter/average.
59 * The low frequency variations enable us to synchronize the client clock
60 * with the server clock because they represent the time variation between
61 * the 2 clocks. Those variations (ie the filtered pcr) are used to compute
62 * the presentation dates for the audio and video frames. With those dates
63 * we can decode (or trash) the MPEG2 stream at "exactly" the same rate
64 * as it is sent by the server and so we keep the synchronization between
65 * the server and the client.
67 * It is a very important matter if you want to avoid underflow or overflow
68 * in all the FIFOs, but it may be not enough.
71 /* i_cr_average : Maximum number of samples used to compute the
72 * dynamic average value.
73 * We use the following formula :
74 * new_average = (old_average * c_average + new_sample_value) / (c_average +1)
78 /*****************************************************************************
80 *****************************************************************************/
82 /* Maximum gap allowed between two CRs. */
83 #define CR_MAX_GAP (INT64_C(2000000)*100/9)
85 /* Latency introduced on DVDs with CR == 0 on chapter change - this is from
87 #define CR_MEAN_PTS_GAP (300000)
89 /* Rate (in 1/256) at which we will read faster to try to increase our
90 * internal buffer (if we control the pace of the source).
92 #define CR_BUFFERING_RATE (48)
94 /* Extra internal buffer value (in CLOCK_FREQ)
95 * It is 60s max, remember as it is limited by the size it takes by es_out.c
96 * it can be really large.
98 #define CR_BUFFERING_TARGET (60000000)
100 /*****************************************************************************
102 *****************************************************************************/
105 * This structure holds long term average
115 static void AvgInit( average_t *, int i_divider );
116 static void AvgClean( average_t * );
118 static void AvgReset( average_t * );
119 static void AvgUpdate( average_t *, mtime_t i_value );
120 static mtime_t AvgGet( average_t * );
121 static void AvgRescale( average_t *, int i_divider );
130 static inline clock_point_t clock_point_Create( mtime_t i_stream, mtime_t i_system )
132 clock_point_t p = { .i_stream = i_stream, .i_system = i_system };
137 #define INPUT_CLOCK_LATE_COUNT (3)
145 /* Reference point */
146 bool b_has_reference;
150 * It is used to detect unexpected stream discontinuities */
153 /* Maximal timestamp returned by input_clock_ConvertTS (in system unit) */
156 /* Amount of extra buffering expressed in stream clock */
157 mtime_t i_buffering_duration;
160 mtime_t i_next_drift_update;
163 /* Late statistics */
166 mtime_t pi_value[INPUT_CLOCK_LATE_COUNT];
170 /* Current modifiers */
174 mtime_t i_pause_date;
177 static mtime_t ClockStreamToSystem( input_clock_t *, mtime_t i_stream );
178 static mtime_t ClockSystemToStream( input_clock_t *, mtime_t i_system );
180 static mtime_t ClockGetTsOffset( input_clock_t * );
182 /*****************************************************************************
183 * input_clock_New: create a new clock
184 *****************************************************************************/
185 input_clock_t *input_clock_New( int i_rate )
187 input_clock_t *cl = malloc( sizeof(*cl) );
191 vlc_mutex_init( &cl->lock );
192 cl->b_has_reference = false;
193 cl->ref = clock_point_Create( VLC_TS_INVALID, VLC_TS_INVALID );
195 cl->last = clock_point_Create( VLC_TS_INVALID, VLC_TS_INVALID );
197 cl->i_ts_max = VLC_TS_INVALID;
199 cl->i_buffering_duration = 0;
201 cl->i_next_drift_update = VLC_TS_INVALID;
202 AvgInit( &cl->drift, 10 );
204 cl->late.i_index = 0;
205 for( int i = 0; i < INPUT_CLOCK_LATE_COUNT; i++ )
206 cl->late.pi_value[i] = 0;
210 cl->b_paused = false;
211 cl->i_pause_date = VLC_TS_INVALID;
216 /*****************************************************************************
217 * input_clock_Delete: destroy a new clock
218 *****************************************************************************/
219 void input_clock_Delete( input_clock_t *cl )
221 AvgClean( &cl->drift );
222 vlc_mutex_destroy( &cl->lock );
226 /*****************************************************************************
227 * input_clock_Update: manages a clock reference
229 * i_ck_stream: date in stream clock
230 * i_ck_system: date in system clock
231 *****************************************************************************/
232 void input_clock_Update( input_clock_t *cl, vlc_object_t *p_log,
234 bool b_can_pace_control, bool b_buffering_allowed,
235 mtime_t i_ck_stream, mtime_t i_ck_system )
237 bool b_reset_reference = false;
239 assert( i_ck_stream > VLC_TS_INVALID && i_ck_system > VLC_TS_INVALID );
241 vlc_mutex_lock( &cl->lock );
243 if( !cl->b_has_reference )
246 b_reset_reference= true;
248 else if( cl->last.i_stream > VLC_TS_INVALID &&
249 ( (cl->last.i_stream - i_ck_stream) > CR_MAX_GAP ||
250 (cl->last.i_stream - i_ck_stream) < -CR_MAX_GAP ) )
252 /* Stream discontinuity, for which we haven't received a
253 * warning from the stream control facilities (dd-edited
255 msg_Warn( p_log, "clock gap, unexpected stream discontinuity" );
256 cl->i_ts_max = VLC_TS_INVALID;
259 msg_Warn( p_log, "feeding synchro with a new reference point trying to recover from clock gap" );
260 b_reset_reference= true;
264 if( b_reset_reference )
266 cl->i_next_drift_update = VLC_TS_INVALID;
267 AvgReset( &cl->drift );
269 /* Feed synchro with a new reference point. */
270 cl->b_has_reference = true;
271 cl->ref = clock_point_Create( i_ck_stream,
272 __MAX( cl->i_ts_max + CR_MEAN_PTS_GAP, i_ck_system ) );
275 /* Compute the drift between the stream clock and the system clock
276 * when we don't control the source pace */
277 if( !b_can_pace_control && cl->i_next_drift_update < i_ck_system )
279 const mtime_t i_converted = ClockSystemToStream( cl, i_ck_system );
281 AvgUpdate( &cl->drift, i_converted - i_ck_stream );
283 cl->i_next_drift_update = i_ck_system + CLOCK_FREQ/5; /* FIXME why that */
286 /* Update the extra buffering value */
287 if( !b_can_pace_control || b_reset_reference )
289 cl->i_buffering_duration = 0;
291 else if( b_buffering_allowed )
293 /* Try to bufferize more than necessary by reading
294 * CR_BUFFERING_RATE/256 faster until we have CR_BUFFERING_TARGET.
296 const mtime_t i_duration = __MAX( i_ck_stream - cl->last.i_stream, 0 );
298 cl->i_buffering_duration += ( i_duration * CR_BUFFERING_RATE + 255 ) / 256;
299 if( cl->i_buffering_duration > CR_BUFFERING_TARGET )
300 cl->i_buffering_duration = CR_BUFFERING_TARGET;
302 //fprintf( stderr, "input_clock_Update: %d :: %lld\n", b_buffering_allowed, cl->i_buffering_duration/1000 );
305 cl->last = clock_point_Create( i_ck_stream, i_ck_system );
307 /* It does not take the decoder latency into account but it is not really
308 * the goal of the clock here */
309 const mtime_t i_system_expected = ClockStreamToSystem( cl, i_ck_stream + AvgGet( &cl->drift ) );
310 const mtime_t i_late = ( i_ck_system - cl->i_pts_delay ) - i_system_expected;
311 *pb_late = i_late > 0;
314 cl->late.pi_value[cl->late.i_index] = i_late;
315 cl->late.i_index = ( cl->late.i_index + 1 ) % INPUT_CLOCK_LATE_COUNT;
318 vlc_mutex_unlock( &cl->lock );
321 /*****************************************************************************
323 *****************************************************************************/
324 void input_clock_Reset( input_clock_t *cl )
326 vlc_mutex_lock( &cl->lock );
328 cl->b_has_reference = false;
329 cl->ref = clock_point_Create( VLC_TS_INVALID, VLC_TS_INVALID );
330 cl->i_ts_max = VLC_TS_INVALID;
332 vlc_mutex_unlock( &cl->lock );
335 /*****************************************************************************
336 * input_clock_ChangeRate:
337 *****************************************************************************/
338 void input_clock_ChangeRate( input_clock_t *cl, int i_rate )
340 vlc_mutex_lock( &cl->lock );
342 if( cl->b_has_reference )
344 /* Move the reference point (as if we were playing at the new rate
346 cl->ref.i_system = cl->last.i_system - (cl->last.i_system - cl->ref.i_system) * i_rate / cl->i_rate;
350 vlc_mutex_unlock( &cl->lock );
353 /*****************************************************************************
354 * input_clock_ChangePause:
355 *****************************************************************************/
356 void input_clock_ChangePause( input_clock_t *cl, bool b_paused, mtime_t i_date )
358 vlc_mutex_lock( &cl->lock );
359 assert( (!cl->b_paused) != (!b_paused) );
363 const mtime_t i_duration = i_date - cl->i_pause_date;
365 if( cl->b_has_reference && i_duration > 0 )
367 cl->ref.i_system += i_duration;
368 cl->last.i_system += i_duration;
371 cl->i_pause_date = i_date;
372 cl->b_paused = b_paused;
374 vlc_mutex_unlock( &cl->lock );
377 /*****************************************************************************
378 * input_clock_GetWakeup
379 *****************************************************************************/
380 mtime_t input_clock_GetWakeup( input_clock_t *cl )
382 mtime_t i_wakeup = 0;
384 vlc_mutex_lock( &cl->lock );
386 /* Synchronized, we can wait */
387 if( cl->b_has_reference )
388 i_wakeup = ClockStreamToSystem( cl, cl->last.i_stream + AvgGet( &cl->drift ) - cl->i_buffering_duration );
390 vlc_mutex_unlock( &cl->lock );
395 /*****************************************************************************
396 * input_clock_ConvertTS
397 *****************************************************************************/
398 int input_clock_ConvertTS( input_clock_t *cl,
399 int *pi_rate, mtime_t *pi_ts0, mtime_t *pi_ts1,
403 vlc_mutex_lock( &cl->lock );
406 *pi_rate = cl->i_rate;
408 if( !cl->b_has_reference )
410 vlc_mutex_unlock( &cl->lock );
411 *pi_ts0 = VLC_TS_INVALID;
413 *pi_ts1 = VLC_TS_INVALID;
418 const mtime_t i_ts_buffering = cl->i_buffering_duration * cl->i_rate / INPUT_RATE_DEFAULT;
419 const mtime_t i_ts_delay = cl->i_pts_delay + ClockGetTsOffset( cl );
422 if( *pi_ts0 > VLC_TS_INVALID )
424 *pi_ts0 = ClockStreamToSystem( cl, *pi_ts0 + AvgGet( &cl->drift ) );
425 if( *pi_ts0 > cl->i_ts_max )
426 cl->i_ts_max = *pi_ts0;
427 *pi_ts0 += i_ts_delay;
430 /* XXX we do not ipdate i_ts_max on purpose */
431 if( pi_ts1 && *pi_ts1 > VLC_TS_INVALID )
433 *pi_ts1 = ClockStreamToSystem( cl, *pi_ts1 + AvgGet( &cl->drift ) ) +
437 vlc_mutex_unlock( &cl->lock );
439 /* Check ts validity */
440 if( i_ts_bound != INT64_MAX &&
441 *pi_ts0 > VLC_TS_INVALID && *pi_ts0 >= mdate() + i_ts_delay + i_ts_buffering + i_ts_bound )
446 /*****************************************************************************
447 * input_clock_GetRate: Return current rate
448 *****************************************************************************/
449 int input_clock_GetRate( input_clock_t *cl )
453 vlc_mutex_lock( &cl->lock );
455 vlc_mutex_unlock( &cl->lock );
460 int input_clock_GetState( input_clock_t *cl,
461 mtime_t *pi_stream_start, mtime_t *pi_system_start,
462 mtime_t *pi_stream_duration, mtime_t *pi_system_duration )
464 vlc_mutex_lock( &cl->lock );
466 if( !cl->b_has_reference )
468 vlc_mutex_unlock( &cl->lock );
472 *pi_stream_start = cl->ref.i_stream;
473 *pi_system_start = cl->ref.i_system;
475 *pi_stream_duration = cl->last.i_stream - cl->ref.i_stream;
476 *pi_system_duration = cl->last.i_system - cl->ref.i_system;
478 vlc_mutex_unlock( &cl->lock );
483 void input_clock_ChangeSystemOrigin( input_clock_t *cl, mtime_t i_system )
485 vlc_mutex_lock( &cl->lock );
487 assert( cl->b_has_reference );
488 const mtime_t i_offset = i_system - cl->ref.i_system - ClockGetTsOffset( cl );
490 cl->ref.i_system += i_offset;
491 cl->last.i_system += i_offset;
493 vlc_mutex_unlock( &cl->lock );
496 #warning "input_clock_SetJitter needs more work"
497 void input_clock_SetJitter( input_clock_t *cl,
498 mtime_t i_pts_delay, int i_cr_average )
500 vlc_mutex_lock( &cl->lock );
502 /* Update late observations */
503 const mtime_t i_delay_delta = i_pts_delay - cl->i_pts_delay;
504 for( int i = 0; i < INPUT_CLOCK_LATE_COUNT; i++ )
506 if( cl->late.pi_value[i] > 0 )
507 cl->late.pi_value[i] = __MAX( cl->late.pi_value[i] - i_delay_delta, 0 );
510 /* TODO always save the value, and when rebuffering use the new one if smaller
511 * TODO when increasing -> force rebuffering
513 if( cl->i_pts_delay < i_pts_delay )
514 cl->i_pts_delay = i_pts_delay;
517 if( i_cr_average < 10 )
520 if( cl->drift.i_divider != i_cr_average )
521 AvgRescale( &cl->drift, i_cr_average );
523 vlc_mutex_unlock( &cl->lock );
526 mtime_t input_clock_GetJitter( input_clock_t *cl )
528 vlc_mutex_lock( &cl->lock );
530 #if INPUT_CLOCK_LATE_COUNT != 3
531 # error "unsupported INPUT_CLOCK_LATE_COUNT"
533 /* Find the median of the last late values
534 * It works pretty well at rejecting bad values
536 * XXX we only increase pts_delay over time, decreasing it is
537 * not that easy if we want to be robust.
539 const mtime_t *p = cl->late.pi_value;
540 mtime_t i_late_median = p[0] + p[1] + p[2] - __MIN(__MIN(p[0],p[1]),p[2]) - __MAX(__MAX(p[0],p[1]),p[2]);
541 mtime_t i_pts_delay = cl->i_pts_delay ;
543 vlc_mutex_unlock( &cl->lock );
545 return i_pts_delay + i_late_median;
548 /*****************************************************************************
549 * ClockStreamToSystem: converts a movie clock to system date
550 *****************************************************************************/
551 static mtime_t ClockStreamToSystem( input_clock_t *cl, mtime_t i_stream )
553 if( !cl->b_has_reference )
554 return VLC_TS_INVALID;
556 return ( i_stream - cl->ref.i_stream ) * cl->i_rate / INPUT_RATE_DEFAULT +
560 /*****************************************************************************
561 * ClockSystemToStream: converts a system date to movie clock
562 *****************************************************************************
563 * Caution : a valid reference point is needed for this to operate.
564 *****************************************************************************/
565 static mtime_t ClockSystemToStream( input_clock_t *cl, mtime_t i_system )
567 assert( cl->b_has_reference );
568 return ( i_system - cl->ref.i_system ) * INPUT_RATE_DEFAULT / cl->i_rate +
573 * It returns timestamp display offset due to ref/last modfied on rate changes
574 * It ensures that currently converted dates are not changed.
576 static mtime_t ClockGetTsOffset( input_clock_t *cl )
578 return cl->i_pts_delay * ( cl->i_rate - INPUT_RATE_DEFAULT ) / INPUT_RATE_DEFAULT;
581 /*****************************************************************************
582 * Long term average helpers
583 *****************************************************************************/
584 static void AvgInit( average_t *p_avg, int i_divider )
586 p_avg->i_divider = i_divider;
589 static void AvgClean( average_t *p_avg )
593 static void AvgReset( average_t *p_avg )
596 p_avg->i_residue = 0;
599 static void AvgUpdate( average_t *p_avg, mtime_t i_value )
601 const int i_f0 = __MIN( p_avg->i_divider - 1, p_avg->i_count );
602 const int i_f1 = p_avg->i_divider - i_f0;
604 const mtime_t i_tmp = i_f0 * p_avg->i_value + i_f1 * i_value + p_avg->i_residue;
606 p_avg->i_value = i_tmp / p_avg->i_divider;
607 p_avg->i_residue = i_tmp % p_avg->i_divider;
611 static mtime_t AvgGet( average_t *p_avg )
613 return p_avg->i_value;
615 static void AvgRescale( average_t *p_avg, int i_divider )
617 const mtime_t i_tmp = p_avg->i_value * p_avg->i_divider + p_avg->i_residue;
619 p_avg->i_divider = i_divider;
620 p_avg->i_value = i_tmp / p_avg->i_divider;
621 p_avg->i_residue = i_tmp % p_avg->i_divider;