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 /*****************************************************************************
91 *****************************************************************************/
94 * This structure holds long term average
104 static void AvgInit( average_t *, int i_divider );
105 static void AvgClean( average_t * );
107 static void AvgReset( average_t * );
108 static void AvgUpdate( average_t *, mtime_t i_value );
109 static mtime_t AvgGet( average_t * );
110 static void AvgRescale( average_t *, int i_divider );
119 static inline clock_point_t clock_point_Create( mtime_t i_stream, mtime_t i_system )
121 clock_point_t p = { .i_stream = i_stream, .i_system = i_system };
126 #define INPUT_CLOCK_LATE_COUNT (3)
134 /* Reference point */
135 bool b_has_reference;
139 * It is used to detect unexpected stream discontinuities */
142 /* Maximal timestamp returned by input_clock_ConvertTS (in system unit) */
146 mtime_t i_next_drift_update;
149 /* Late statistics */
152 mtime_t pi_value[INPUT_CLOCK_LATE_COUNT];
156 /* Current modifiers */
160 mtime_t i_pause_date;
163 static mtime_t ClockStreamToSystem( input_clock_t *, mtime_t i_stream );
164 static mtime_t ClockSystemToStream( input_clock_t *, mtime_t i_system );
166 static mtime_t ClockGetTsOffset( input_clock_t * );
168 /*****************************************************************************
169 * input_clock_New: create a new clock
170 *****************************************************************************/
171 input_clock_t *input_clock_New( int i_rate )
173 input_clock_t *cl = malloc( sizeof(*cl) );
177 vlc_mutex_init( &cl->lock );
178 cl->b_has_reference = false;
179 cl->ref = clock_point_Create( VLC_TS_INVALID, VLC_TS_INVALID );
181 cl->last = clock_point_Create( VLC_TS_INVALID, VLC_TS_INVALID );
183 cl->i_ts_max = VLC_TS_INVALID;
185 cl->i_next_drift_update = VLC_TS_INVALID;
186 AvgInit( &cl->drift, 10 );
188 cl->late.i_index = 0;
189 for( int i = 0; i < INPUT_CLOCK_LATE_COUNT; i++ )
190 cl->late.pi_value[i] = 0;
194 cl->b_paused = false;
195 cl->i_pause_date = VLC_TS_INVALID;
200 /*****************************************************************************
201 * input_clock_Delete: destroy a new clock
202 *****************************************************************************/
203 void input_clock_Delete( input_clock_t *cl )
205 AvgClean( &cl->drift );
206 vlc_mutex_destroy( &cl->lock );
210 /*****************************************************************************
211 * input_clock_Update: manages a clock reference
213 * i_ck_stream: date in stream clock
214 * i_ck_system: date in system clock
215 *****************************************************************************/
216 void input_clock_Update( input_clock_t *cl, vlc_object_t *p_log,
218 bool b_can_pace_control,
219 mtime_t i_ck_stream, mtime_t i_ck_system )
221 bool b_reset_reference = false;
223 assert( i_ck_stream > VLC_TS_INVALID && i_ck_system > VLC_TS_INVALID );
225 vlc_mutex_lock( &cl->lock );
227 if( !cl->b_has_reference )
230 b_reset_reference= true;
232 else if( cl->last.i_stream > VLC_TS_INVALID &&
233 ( (cl->last.i_stream - i_ck_stream) > CR_MAX_GAP ||
234 (cl->last.i_stream - i_ck_stream) < -CR_MAX_GAP ) )
236 /* Stream discontinuity, for which we haven't received a
237 * warning from the stream control facilities (dd-edited
239 msg_Warn( p_log, "clock gap, unexpected stream discontinuity" );
240 cl->i_ts_max = VLC_TS_INVALID;
243 msg_Warn( p_log, "feeding synchro with a new reference point trying to recover from clock gap" );
244 b_reset_reference= true;
246 if( b_reset_reference )
248 cl->i_next_drift_update = VLC_TS_INVALID;
249 AvgReset( &cl->drift );
251 /* Feed synchro with a new reference point. */
252 cl->b_has_reference = true;
253 cl->ref = clock_point_Create( i_ck_stream,
254 __MAX( cl->i_ts_max + CR_MEAN_PTS_GAP, i_ck_system ) );
257 if( !b_can_pace_control && cl->i_next_drift_update < i_ck_system )
259 const mtime_t i_converted = ClockSystemToStream( cl, i_ck_system );
261 AvgUpdate( &cl->drift, i_converted - i_ck_stream );
263 cl->i_next_drift_update = i_ck_system + CLOCK_FREQ/5; /* FIXME why that */
265 cl->last = clock_point_Create( i_ck_stream, i_ck_system );
267 /* It does not take the decoder latency into account but it is not really
268 * the goal of the clock here */
269 const mtime_t i_system_expected = ClockStreamToSystem( cl, i_ck_stream + AvgGet( &cl->drift ) );
270 const mtime_t i_late = ( i_ck_system - cl->i_pts_delay ) - i_system_expected;
271 *pb_late = i_late > 0;
274 cl->late.pi_value[cl->late.i_index] = i_late;
275 cl->late.i_index = ( cl->late.i_index + 1 ) % INPUT_CLOCK_LATE_COUNT;
278 vlc_mutex_unlock( &cl->lock );
281 /*****************************************************************************
283 *****************************************************************************/
284 void input_clock_Reset( input_clock_t *cl )
286 vlc_mutex_lock( &cl->lock );
288 cl->b_has_reference = false;
289 cl->ref = clock_point_Create( VLC_TS_INVALID, VLC_TS_INVALID );
290 cl->i_ts_max = VLC_TS_INVALID;
292 vlc_mutex_unlock( &cl->lock );
295 /*****************************************************************************
296 * input_clock_ChangeRate:
297 *****************************************************************************/
298 void input_clock_ChangeRate( input_clock_t *cl, int i_rate )
300 vlc_mutex_lock( &cl->lock );
302 if( cl->b_has_reference )
304 /* Move the reference point (as if we were playing at the new rate
306 cl->ref.i_system = cl->last.i_system - (cl->last.i_system - cl->ref.i_system) * i_rate / cl->i_rate;
310 vlc_mutex_unlock( &cl->lock );
313 /*****************************************************************************
314 * input_clock_ChangePause:
315 *****************************************************************************/
316 void input_clock_ChangePause( input_clock_t *cl, bool b_paused, mtime_t i_date )
318 vlc_mutex_lock( &cl->lock );
319 assert( (!cl->b_paused) != (!b_paused) );
323 const mtime_t i_duration = i_date - cl->i_pause_date;
325 if( cl->b_has_reference && i_duration > 0 )
327 cl->ref.i_system += i_duration;
328 cl->last.i_system += i_duration;
331 cl->i_pause_date = i_date;
332 cl->b_paused = b_paused;
334 vlc_mutex_unlock( &cl->lock );
337 /*****************************************************************************
338 * input_clock_GetWakeup
339 *****************************************************************************/
340 mtime_t input_clock_GetWakeup( input_clock_t *cl )
342 mtime_t i_wakeup = 0;
344 vlc_mutex_lock( &cl->lock );
346 /* Synchronized, we can wait */
347 if( cl->b_has_reference )
348 i_wakeup = ClockStreamToSystem( cl, cl->last.i_stream + AvgGet( &cl->drift ) );
350 vlc_mutex_unlock( &cl->lock );
355 /*****************************************************************************
356 * input_clock_ConvertTS
357 *****************************************************************************/
358 int input_clock_ConvertTS( input_clock_t *cl,
359 int *pi_rate, mtime_t *pi_ts0, mtime_t *pi_ts1,
363 vlc_mutex_lock( &cl->lock );
366 *pi_rate = cl->i_rate;
368 if( !cl->b_has_reference )
370 vlc_mutex_unlock( &cl->lock );
371 *pi_ts0 = VLC_TS_INVALID;
373 *pi_ts1 = VLC_TS_INVALID;
378 const mtime_t i_ts_delay = cl->i_pts_delay + ClockGetTsOffset( cl );
381 if( *pi_ts0 > VLC_TS_INVALID )
383 *pi_ts0 = ClockStreamToSystem( cl, *pi_ts0 + AvgGet( &cl->drift ) );
384 if( *pi_ts0 > cl->i_ts_max )
385 cl->i_ts_max = *pi_ts0;
386 *pi_ts0 += i_ts_delay;
389 /* XXX we do not ipdate i_ts_max on purpose */
390 if( pi_ts1 && *pi_ts1 > VLC_TS_INVALID )
392 *pi_ts1 = ClockStreamToSystem( cl, *pi_ts1 + AvgGet( &cl->drift ) ) +
396 vlc_mutex_unlock( &cl->lock );
398 /* Check ts validity */
399 if( i_ts_bound != INT64_MAX &&
400 *pi_ts0 > VLC_TS_INVALID && *pi_ts0 >= mdate() + i_ts_delay + i_ts_bound )
405 /*****************************************************************************
406 * input_clock_GetRate: Return current rate
407 *****************************************************************************/
408 int input_clock_GetRate( input_clock_t *cl )
412 vlc_mutex_lock( &cl->lock );
414 vlc_mutex_unlock( &cl->lock );
419 int input_clock_GetState( input_clock_t *cl,
420 mtime_t *pi_stream_start, mtime_t *pi_system_start,
421 mtime_t *pi_stream_duration, mtime_t *pi_system_duration )
423 vlc_mutex_lock( &cl->lock );
425 if( !cl->b_has_reference )
427 vlc_mutex_unlock( &cl->lock );
431 *pi_stream_start = cl->ref.i_stream;
432 *pi_system_start = cl->ref.i_system;
434 *pi_stream_duration = cl->last.i_stream - cl->ref.i_stream;
435 *pi_system_duration = cl->last.i_system - cl->ref.i_system;
437 vlc_mutex_unlock( &cl->lock );
442 void input_clock_ChangeSystemOrigin( input_clock_t *cl, mtime_t i_system )
444 vlc_mutex_lock( &cl->lock );
446 assert( cl->b_has_reference );
447 const mtime_t i_offset = i_system - cl->ref.i_system - ClockGetTsOffset( cl );
449 cl->ref.i_system += i_offset;
450 cl->last.i_system += i_offset;
452 vlc_mutex_unlock( &cl->lock );
455 #warning "input_clock_SetJitter needs more work"
456 void input_clock_SetJitter( input_clock_t *cl,
457 mtime_t i_pts_delay, int i_cr_average )
459 vlc_mutex_lock( &cl->lock );
461 /* Update late observations */
462 const mtime_t i_delay_delta = i_pts_delay - cl->i_pts_delay;
463 for( int i = 0; i < INPUT_CLOCK_LATE_COUNT; i++ )
465 if( cl->late.pi_value[i] > 0 )
466 cl->late.pi_value[i] = __MAX( cl->late.pi_value[i] - i_delay_delta, 0 );
469 /* TODO always save the value, and when rebuffering use the new one if smaller
470 * TODO when increasing -> force rebuffering
472 if( cl->i_pts_delay < i_pts_delay )
473 cl->i_pts_delay = i_pts_delay;
476 if( i_cr_average < 10 )
479 if( cl->drift.i_divider != i_cr_average )
480 AvgRescale( &cl->drift, i_cr_average );
482 vlc_mutex_unlock( &cl->lock );
485 mtime_t input_clock_GetJitter( input_clock_t *cl )
487 vlc_mutex_lock( &cl->lock );
489 #if INPUT_CLOCK_LATE_COUNT != 3
490 # error "unsupported INPUT_CLOCK_LATE_COUNT"
492 /* Find the median of the last late values
493 * It works pretty well at rejecting bad values
495 * XXX we only increase pts_delay over time, decreasing it is
496 * not that easy if we want to be robust.
498 const mtime_t *p = cl->late.pi_value;
499 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]);
500 mtime_t i_pts_delay = cl->i_pts_delay ;
502 vlc_mutex_unlock( &cl->lock );
504 return i_pts_delay + i_late_median;
507 /*****************************************************************************
508 * ClockStreamToSystem: converts a movie clock to system date
509 *****************************************************************************/
510 static mtime_t ClockStreamToSystem( input_clock_t *cl, mtime_t i_stream )
512 if( !cl->b_has_reference )
513 return VLC_TS_INVALID;
515 return ( i_stream - cl->ref.i_stream ) * cl->i_rate / INPUT_RATE_DEFAULT +
519 /*****************************************************************************
520 * ClockSystemToStream: converts a system date to movie clock
521 *****************************************************************************
522 * Caution : a valid reference point is needed for this to operate.
523 *****************************************************************************/
524 static mtime_t ClockSystemToStream( input_clock_t *cl, mtime_t i_system )
526 assert( cl->b_has_reference );
527 return ( i_system - cl->ref.i_system ) * INPUT_RATE_DEFAULT / cl->i_rate +
532 * It returns timestamp display offset due to ref/last modfied on rate changes
533 * It ensures that currently converted dates are not changed.
535 static mtime_t ClockGetTsOffset( input_clock_t *cl )
537 return cl->i_pts_delay * ( cl->i_rate - INPUT_RATE_DEFAULT ) / INPUT_RATE_DEFAULT;
540 /*****************************************************************************
541 * Long term average helpers
542 *****************************************************************************/
543 static void AvgInit( average_t *p_avg, int i_divider )
545 p_avg->i_divider = i_divider;
548 static void AvgClean( average_t *p_avg )
552 static void AvgReset( average_t *p_avg )
555 p_avg->i_residue = 0;
558 static void AvgUpdate( average_t *p_avg, mtime_t i_value )
560 const int i_f0 = __MIN( p_avg->i_divider - 1, p_avg->i_count );
561 const int i_f1 = p_avg->i_divider - i_f0;
563 const mtime_t i_tmp = i_f0 * p_avg->i_value + i_f1 * i_value + p_avg->i_residue;
565 p_avg->i_value = i_tmp / p_avg->i_divider;
566 p_avg->i_residue = i_tmp % p_avg->i_divider;
570 static mtime_t AvgGet( average_t *p_avg )
572 return p_avg->i_value;
574 static void AvgRescale( average_t *p_avg, int i_divider )
576 const mtime_t i_tmp = p_avg->i_value * p_avg->i_divider + p_avg->i_residue;
578 p_avg->i_divider = i_divider;
579 p_avg->i_value = i_tmp / p_avg->i_divider;
580 p_avg->i_residue = i_tmp % p_avg->i_divider;