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 /*****************************************************************************
167 * input_clock_New: create a new clock
168 *****************************************************************************/
169 input_clock_t *input_clock_New( int i_rate )
171 input_clock_t *cl = malloc( sizeof(*cl) );
175 vlc_mutex_init( &cl->lock );
176 cl->b_has_reference = false;
177 cl->ref = clock_point_Create( VLC_TS_INVALID, VLC_TS_INVALID );
179 cl->last = clock_point_Create( VLC_TS_INVALID, VLC_TS_INVALID );
181 cl->i_ts_max = VLC_TS_INVALID;
183 cl->i_next_drift_update = VLC_TS_INVALID;
184 AvgInit( &cl->drift, 10 );
186 cl->late.i_index = 0;
187 for( int i = 0; i < INPUT_CLOCK_LATE_COUNT; i++ )
188 cl->late.pi_value[i] = 0;
192 cl->b_paused = false;
193 cl->i_pause_date = VLC_TS_INVALID;
198 /*****************************************************************************
199 * input_clock_Delete: destroy a new clock
200 *****************************************************************************/
201 void input_clock_Delete( input_clock_t *cl )
203 AvgClean( &cl->drift );
204 vlc_mutex_destroy( &cl->lock );
208 /*****************************************************************************
209 * input_clock_Update: manages a clock reference
211 * i_ck_stream: date in stream clock
212 * i_ck_system: date in system clock
213 *****************************************************************************/
214 void input_clock_Update( input_clock_t *cl, vlc_object_t *p_log,
216 bool b_can_pace_control,
217 mtime_t i_ck_stream, mtime_t i_ck_system )
219 bool b_reset_reference = false;
221 assert( i_ck_stream > VLC_TS_INVALID && i_ck_system > VLC_TS_INVALID );
223 vlc_mutex_lock( &cl->lock );
225 if( !cl->b_has_reference )
228 b_reset_reference= true;
230 else if( cl->last.i_stream > VLC_TS_INVALID &&
231 ( (cl->last.i_stream - i_ck_stream) > CR_MAX_GAP ||
232 (cl->last.i_stream - i_ck_stream) < -CR_MAX_GAP ) )
234 /* Stream discontinuity, for which we haven't received a
235 * warning from the stream control facilities (dd-edited
237 msg_Warn( p_log, "clock gap, unexpected stream discontinuity" );
238 cl->i_ts_max = VLC_TS_INVALID;
241 msg_Warn( p_log, "feeding synchro with a new reference point trying to recover from clock gap" );
242 b_reset_reference= true;
244 if( b_reset_reference )
246 cl->i_next_drift_update = VLC_TS_INVALID;
247 AvgReset( &cl->drift );
249 /* Feed synchro with a new reference point. */
250 cl->b_has_reference = true;
251 cl->ref = clock_point_Create( i_ck_stream,
252 __MAX( cl->i_ts_max + CR_MEAN_PTS_GAP, i_ck_system ) );
255 if( !b_can_pace_control && cl->i_next_drift_update < i_ck_system )
257 const mtime_t i_converted = ClockSystemToStream( cl, i_ck_system );
259 AvgUpdate( &cl->drift, i_converted - i_ck_stream );
261 cl->i_next_drift_update = i_ck_system + CLOCK_FREQ/5; /* FIXME why that */
263 cl->last = clock_point_Create( i_ck_stream, i_ck_system );
265 /* It does not take the decoder latency into account but it is not really
266 * the goal of the clock here */
267 const mtime_t i_system_expected = ClockStreamToSystem( cl, i_ck_stream + AvgGet( &cl->drift ) );
268 const mtime_t i_late = ( i_ck_system - cl->i_pts_delay ) - i_system_expected;
269 *pb_late = i_late > 0;
272 cl->late.pi_value[cl->late.i_index] = i_late;
273 cl->late.i_index = ( cl->late.i_index + 1 ) % INPUT_CLOCK_LATE_COUNT;
276 vlc_mutex_unlock( &cl->lock );
279 /*****************************************************************************
281 *****************************************************************************/
282 void input_clock_Reset( input_clock_t *cl )
284 vlc_mutex_lock( &cl->lock );
286 cl->b_has_reference = false;
287 cl->ref = clock_point_Create( VLC_TS_INVALID, VLC_TS_INVALID );
288 cl->i_ts_max = VLC_TS_INVALID;
290 vlc_mutex_unlock( &cl->lock );
293 /*****************************************************************************
294 * input_clock_ChangeRate:
295 *****************************************************************************/
296 void input_clock_ChangeRate( input_clock_t *cl, int i_rate )
298 vlc_mutex_lock( &cl->lock );
300 /* Move the reference point */
301 if( cl->b_has_reference )
303 cl->last.i_system = ClockStreamToSystem( cl, cl->last.i_stream + AvgGet( &cl->drift ) );
309 vlc_mutex_unlock( &cl->lock );
312 /*****************************************************************************
313 * input_clock_ChangePause:
314 *****************************************************************************/
315 void input_clock_ChangePause( input_clock_t *cl, bool b_paused, mtime_t i_date )
317 vlc_mutex_lock( &cl->lock );
318 assert( (!cl->b_paused) != (!b_paused) );
322 const mtime_t i_duration = i_date - cl->i_pause_date;
324 if( cl->b_has_reference && i_duration > 0 )
326 cl->ref.i_system += i_duration;
327 cl->last.i_system += i_duration;
330 cl->i_pause_date = i_date;
331 cl->b_paused = b_paused;
333 vlc_mutex_unlock( &cl->lock );
336 /*****************************************************************************
337 * input_clock_GetWakeup
338 *****************************************************************************/
339 mtime_t input_clock_GetWakeup( input_clock_t *cl )
341 mtime_t i_wakeup = 0;
343 vlc_mutex_lock( &cl->lock );
345 /* Synchronized, we can wait */
346 if( cl->b_has_reference )
347 i_wakeup = ClockStreamToSystem( cl, cl->last.i_stream + AvgGet( &cl->drift ) );
349 vlc_mutex_unlock( &cl->lock );
354 /*****************************************************************************
355 * input_clock_ConvertTS
356 *****************************************************************************/
357 int input_clock_ConvertTS( input_clock_t *cl,
358 int *pi_rate, mtime_t *pi_ts0, mtime_t *pi_ts1,
364 vlc_mutex_lock( &cl->lock );
367 *pi_rate = cl->i_rate;
369 if( !cl->b_has_reference )
371 vlc_mutex_unlock( &cl->lock );
372 *pi_ts0 = VLC_TS_INVALID;
374 *pi_ts1 = VLC_TS_INVALID;
379 if( *pi_ts0 > VLC_TS_INVALID )
381 *pi_ts0 = ClockStreamToSystem( cl, *pi_ts0 + AvgGet( &cl->drift ) );
382 if( *pi_ts0 > cl->i_ts_max )
383 cl->i_ts_max = *pi_ts0;
384 *pi_ts0 += cl->i_pts_delay;
387 /* XXX we do not ipdate i_ts_max on purpose */
388 if( pi_ts1 && *pi_ts1 > VLC_TS_INVALID )
390 *pi_ts1 = ClockStreamToSystem( cl, *pi_ts1 + AvgGet( &cl->drift ) ) +
394 i_pts_delay = cl->i_pts_delay;
395 vlc_mutex_unlock( &cl->lock );
397 /* Check ts validity */
398 if( i_ts_bound != INT64_MAX &&
399 *pi_ts0 > VLC_TS_INVALID && *pi_ts0 >= mdate() + i_pts_delay + i_ts_bound )
404 /*****************************************************************************
405 * input_clock_GetRate: Return current rate
406 *****************************************************************************/
407 int input_clock_GetRate( input_clock_t *cl )
411 vlc_mutex_lock( &cl->lock );
413 vlc_mutex_unlock( &cl->lock );
418 int input_clock_GetState( input_clock_t *cl,
419 mtime_t *pi_stream_start, mtime_t *pi_system_start,
420 mtime_t *pi_stream_duration, mtime_t *pi_system_duration )
422 vlc_mutex_lock( &cl->lock );
424 if( !cl->b_has_reference )
426 vlc_mutex_unlock( &cl->lock );
430 *pi_stream_start = cl->ref.i_stream;
431 *pi_system_start = cl->ref.i_system;
433 *pi_stream_duration = cl->last.i_stream - cl->ref.i_stream;
434 *pi_system_duration = cl->last.i_system - cl->ref.i_system;
436 vlc_mutex_unlock( &cl->lock );
441 void input_clock_ChangeSystemOrigin( input_clock_t *cl, mtime_t i_system )
443 vlc_mutex_lock( &cl->lock );
445 assert( cl->b_has_reference );
446 const mtime_t i_offset = i_system - cl->ref.i_system;
448 cl->ref.i_system += i_offset;
449 cl->last.i_system += i_offset;
451 vlc_mutex_unlock( &cl->lock );
454 #warning "input_clock_SetJitter needs more work"
455 void input_clock_SetJitter( input_clock_t *cl,
456 mtime_t i_pts_delay, int i_cr_average )
458 vlc_mutex_lock( &cl->lock );
460 /* Update late observations */
461 const mtime_t i_delay_delta = i_pts_delay - cl->i_pts_delay;
462 for( int i = 0; i < INPUT_CLOCK_LATE_COUNT; i++ )
464 if( cl->late.pi_value[i] > 0 )
465 cl->late.pi_value[i] = __MAX( cl->late.pi_value[i] - i_delay_delta, 0 );
468 /* TODO always save the value, and when rebuffering use the new one if smaller
469 * TODO when increasing -> force rebuffering
471 if( cl->i_pts_delay < i_pts_delay )
472 cl->i_pts_delay = i_pts_delay;
475 if( i_cr_average < 10 )
478 if( cl->drift.i_divider != i_cr_average )
479 AvgRescale( &cl->drift, i_cr_average );
481 vlc_mutex_unlock( &cl->lock );
484 mtime_t input_clock_GetJitter( input_clock_t *cl )
486 vlc_mutex_lock( &cl->lock );
488 #if INPUT_CLOCK_LATE_COUNT != 3
489 # error "unsupported INPUT_CLOCK_LATE_COUNT"
491 /* Find the median of the last late values
492 * It works pretty well at rejecting bad values
494 * XXX we only increase pts_delay over time, decreasing it is
495 * not that easy if we want to be robust.
497 const mtime_t *p = cl->late.pi_value;
498 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]);
499 mtime_t i_pts_delay = cl->i_pts_delay ;
501 vlc_mutex_unlock( &cl->lock );
503 return i_pts_delay + i_late_median;
506 /*****************************************************************************
507 * ClockStreamToSystem: converts a movie clock to system date
508 *****************************************************************************/
509 static mtime_t ClockStreamToSystem( input_clock_t *cl, mtime_t i_stream )
511 if( !cl->b_has_reference )
512 return VLC_TS_INVALID;
514 return ( i_stream - cl->ref.i_stream ) * cl->i_rate / INPUT_RATE_DEFAULT +
518 /*****************************************************************************
519 * ClockSystemToStream: converts a system date to movie clock
520 *****************************************************************************
521 * Caution : a valid reference point is needed for this to operate.
522 *****************************************************************************/
523 static mtime_t ClockSystemToStream( input_clock_t *cl, mtime_t i_system )
525 assert( cl->b_has_reference );
526 return ( i_system - cl->ref.i_system ) * INPUT_RATE_DEFAULT / cl->i_rate +
530 /*****************************************************************************
531 * Long term average helpers
532 *****************************************************************************/
533 static void AvgInit( average_t *p_avg, int i_divider )
535 p_avg->i_divider = i_divider;
538 static void AvgClean( average_t *p_avg )
542 static void AvgReset( average_t *p_avg )
545 p_avg->i_residue = 0;
548 static void AvgUpdate( average_t *p_avg, mtime_t i_value )
550 const int i_f0 = __MIN( p_avg->i_divider - 1, p_avg->i_count );
551 const int i_f1 = p_avg->i_divider - i_f0;
553 const mtime_t i_tmp = i_f0 * p_avg->i_value + i_f1 * i_value + p_avg->i_residue;
555 p_avg->i_value = i_tmp / p_avg->i_divider;
556 p_avg->i_residue = i_tmp % p_avg->i_divider;
560 static mtime_t AvgGet( average_t *p_avg )
562 return p_avg->i_value;
564 static void AvgRescale( average_t *p_avg, int i_divider )
566 const mtime_t i_tmp = p_avg->i_value * p_avg->i_divider + p_avg->i_residue;
568 p_avg->i_divider = i_divider;
569 p_avg->i_value = i_tmp / p_avg->i_divider;
570 p_avg->i_residue = i_tmp % p_avg->i_divider;