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 };
131 /* Reference point */
132 bool b_has_reference;
136 * It is used to detect unexpected stream discontinuities */
139 /* Maximal timestamp returned by input_clock_ConvertTS (in system unit) */
143 mtime_t i_next_drift_update;
146 /* Current modifiers */
150 mtime_t i_pause_date;
153 static mtime_t ClockStreamToSystem( input_clock_t *, mtime_t i_stream );
154 static mtime_t ClockSystemToStream( input_clock_t *, mtime_t i_system );
156 /*****************************************************************************
157 * input_clock_New: create a new clock
158 *****************************************************************************/
159 input_clock_t *input_clock_New( int i_rate )
161 input_clock_t *cl = malloc( sizeof(*cl) );
165 vlc_mutex_init( &cl->lock );
166 cl->b_has_reference = false;
167 cl->ref = clock_point_Create( VLC_TS_INVALID, VLC_TS_INVALID );
169 cl->last = clock_point_Create( VLC_TS_INVALID, VLC_TS_INVALID );
171 cl->i_ts_max = VLC_TS_INVALID;
173 cl->i_next_drift_update = VLC_TS_INVALID;
174 AvgInit( &cl->drift, 10 );
178 cl->b_paused = false;
179 cl->i_pause_date = VLC_TS_INVALID;
184 /*****************************************************************************
185 * input_clock_Delete: destroy a new clock
186 *****************************************************************************/
187 void input_clock_Delete( input_clock_t *cl )
189 AvgClean( &cl->drift );
190 vlc_mutex_destroy( &cl->lock );
194 /*****************************************************************************
195 * input_clock_Update: manages a clock reference
197 * i_ck_stream: date in stream clock
198 * i_ck_system: date in system clock
199 *****************************************************************************/
200 void input_clock_Update( input_clock_t *cl,
201 vlc_object_t *p_log, bool b_can_pace_control,
202 mtime_t i_ck_stream, mtime_t i_ck_system )
204 bool b_reset_reference = false;
206 assert( i_ck_stream > VLC_TS_INVALID && i_ck_system > VLC_TS_INVALID );
208 vlc_mutex_lock( &cl->lock );
210 if( !cl->b_has_reference )
213 b_reset_reference= true;
215 else if( cl->last.i_stream > VLC_TS_INVALID &&
216 ( (cl->last.i_stream - i_ck_stream) > CR_MAX_GAP ||
217 (cl->last.i_stream - i_ck_stream) < -CR_MAX_GAP ) )
219 /* Stream discontinuity, for which we haven't received a
220 * warning from the stream control facilities (dd-edited
222 msg_Warn( p_log, "clock gap, unexpected stream discontinuity" );
223 cl->i_ts_max = VLC_TS_INVALID;
226 msg_Warn( p_log, "feeding synchro with a new reference point trying to recover from clock gap" );
227 b_reset_reference= true;
229 if( b_reset_reference )
231 cl->i_next_drift_update = VLC_TS_INVALID;
232 AvgReset( &cl->drift );
234 /* Feed synchro with a new reference point. */
235 cl->b_has_reference = true;
236 cl->ref = clock_point_Create( i_ck_stream,
237 __MAX( cl->i_ts_max + CR_MEAN_PTS_GAP, i_ck_system ) );
240 if( !b_can_pace_control && cl->i_next_drift_update < i_ck_system )
242 const mtime_t i_converted = ClockSystemToStream( cl, i_ck_system );
244 AvgUpdate( &cl->drift, i_converted - i_ck_stream );
246 cl->i_next_drift_update = i_ck_system + CLOCK_FREQ/5; /* FIXME why that */
248 cl->last = clock_point_Create( i_ck_stream, i_ck_system );
250 vlc_mutex_unlock( &cl->lock );
253 /*****************************************************************************
255 *****************************************************************************/
256 void input_clock_Reset( input_clock_t *cl )
258 vlc_mutex_lock( &cl->lock );
260 cl->b_has_reference = false;
261 cl->ref = clock_point_Create( VLC_TS_INVALID, VLC_TS_INVALID );
262 cl->i_ts_max = VLC_TS_INVALID;
264 vlc_mutex_unlock( &cl->lock );
267 /*****************************************************************************
268 * input_clock_ChangeRate:
269 *****************************************************************************/
270 void input_clock_ChangeRate( input_clock_t *cl, int i_rate )
272 vlc_mutex_lock( &cl->lock );
274 /* Move the reference point */
275 if( cl->b_has_reference )
277 cl->last.i_system = ClockStreamToSystem( cl, cl->last.i_stream );
283 vlc_mutex_unlock( &cl->lock );
286 /*****************************************************************************
287 * input_clock_ChangePause:
288 *****************************************************************************/
289 void input_clock_ChangePause( input_clock_t *cl, bool b_paused, mtime_t i_date )
291 vlc_mutex_lock( &cl->lock );
292 assert( (!cl->b_paused) != (!b_paused) );
296 const mtime_t i_duration = i_date - cl->i_pause_date;
298 if( cl->b_has_reference && i_duration > 0 )
300 cl->ref.i_system += i_duration;
301 cl->last.i_system += i_duration;
304 cl->i_pause_date = i_date;
305 cl->b_paused = b_paused;
307 vlc_mutex_unlock( &cl->lock );
310 /*****************************************************************************
311 * input_clock_GetWakeup
312 *****************************************************************************/
313 mtime_t input_clock_GetWakeup( input_clock_t *cl )
315 mtime_t i_wakeup = 0;
317 vlc_mutex_lock( &cl->lock );
319 /* Synchronized, we can wait */
320 if( cl->b_has_reference )
321 i_wakeup = ClockStreamToSystem( cl, cl->last.i_stream );
323 vlc_mutex_unlock( &cl->lock );
328 /*****************************************************************************
329 * input_clock_ConvertTS
330 *****************************************************************************/
331 int input_clock_ConvertTS( input_clock_t *cl,
332 int *pi_rate, mtime_t *pi_ts0, mtime_t *pi_ts1,
338 vlc_mutex_lock( &cl->lock );
341 *pi_rate = cl->i_rate;
343 if( !cl->b_has_reference )
345 vlc_mutex_unlock( &cl->lock );
346 *pi_ts0 = VLC_TS_INVALID;
348 *pi_ts1 = VLC_TS_INVALID;
353 if( *pi_ts0 > VLC_TS_INVALID )
355 *pi_ts0 = ClockStreamToSystem( cl, *pi_ts0 + AvgGet( &cl->drift ) );
356 if( *pi_ts0 > cl->i_ts_max )
357 cl->i_ts_max = *pi_ts0;
358 *pi_ts0 += cl->i_pts_delay;
361 /* XXX we do not ipdate i_ts_max on purpose */
362 if( pi_ts1 && *pi_ts1 > VLC_TS_INVALID )
364 *pi_ts1 = ClockStreamToSystem( cl, *pi_ts1 + AvgGet( &cl->drift ) ) +
368 i_pts_delay = cl->i_pts_delay;
369 vlc_mutex_unlock( &cl->lock );
371 /* Check ts validity */
372 if( i_ts_bound != INT64_MAX &&
373 *pi_ts0 > VLC_TS_INVALID && *pi_ts0 >= mdate() + cl->i_pts_delay + i_ts_bound )
378 /*****************************************************************************
379 * input_clock_GetRate: Return current rate
380 *****************************************************************************/
381 int input_clock_GetRate( input_clock_t *cl )
385 vlc_mutex_lock( &cl->lock );
387 vlc_mutex_unlock( &cl->lock );
392 int input_clock_GetState( input_clock_t *cl,
393 mtime_t *pi_stream_start, mtime_t *pi_system_start,
394 mtime_t *pi_stream_duration, mtime_t *pi_system_duration )
396 vlc_mutex_lock( &cl->lock );
398 if( !cl->b_has_reference )
400 vlc_mutex_unlock( &cl->lock );
404 *pi_stream_start = cl->ref.i_stream;
405 *pi_system_start = cl->ref.i_system;
407 *pi_stream_duration = cl->last.i_stream - cl->ref.i_stream;
408 *pi_system_duration = cl->last.i_system - cl->ref.i_system;
410 vlc_mutex_unlock( &cl->lock );
415 void input_clock_ChangeSystemOrigin( input_clock_t *cl, mtime_t i_system )
417 vlc_mutex_lock( &cl->lock );
419 assert( cl->b_has_reference );
420 const mtime_t i_offset = i_system - cl->ref.i_system;
422 cl->ref.i_system += i_offset;
423 cl->last.i_system += i_offset;
425 vlc_mutex_unlock( &cl->lock );
428 #warning "input_clock_SetJitter needs more work"
429 void input_clock_SetJitter( input_clock_t *cl,
430 mtime_t i_pts_delay, int i_cr_average )
432 vlc_mutex_lock( &cl->lock );
434 /* TODO always save the value, and when rebuffering use the new one if smaller
435 * TODO when increasing -> force rebuffering
437 if( cl->i_pts_delay < i_pts_delay )
438 cl->i_pts_delay = i_pts_delay;
441 if( i_cr_average < 10 )
444 if( cl->drift.i_divider != i_cr_average )
445 AvgRescale( &cl->drift, i_cr_average );
447 vlc_mutex_unlock( &cl->lock );
450 /*****************************************************************************
451 * ClockStreamToSystem: converts a movie clock to system date
452 *****************************************************************************/
453 static mtime_t ClockStreamToSystem( input_clock_t *cl, mtime_t i_stream )
455 if( !cl->b_has_reference )
456 return VLC_TS_INVALID;
458 return ( i_stream - cl->ref.i_stream ) * cl->i_rate / INPUT_RATE_DEFAULT +
462 /*****************************************************************************
463 * ClockSystemToStream: converts a system date to movie clock
464 *****************************************************************************
465 * Caution : a valid reference point is needed for this to operate.
466 *****************************************************************************/
467 static mtime_t ClockSystemToStream( input_clock_t *cl, mtime_t i_system )
469 assert( cl->b_has_reference );
470 return ( i_system - cl->ref.i_system ) * INPUT_RATE_DEFAULT / cl->i_rate +
474 /*****************************************************************************
475 * Long term average helpers
476 *****************************************************************************/
477 static void AvgInit( average_t *p_avg, int i_divider )
479 p_avg->i_divider = i_divider;
482 static void AvgClean( average_t *p_avg )
486 static void AvgReset( average_t *p_avg )
489 p_avg->i_residue = 0;
492 static void AvgUpdate( average_t *p_avg, mtime_t i_value )
494 const int i_f0 = __MIN( p_avg->i_divider - 1, p_avg->i_count );
495 const int i_f1 = p_avg->i_divider - i_f0;
497 const mtime_t i_tmp = i_f0 * p_avg->i_value + i_f1 * i_value + p_avg->i_residue;
499 p_avg->i_value = i_tmp / p_avg->i_divider;
500 p_avg->i_residue = i_tmp % p_avg->i_divider;
504 static mtime_t AvgGet( average_t *p_avg )
506 return p_avg->i_value;
508 static void AvgRescale( average_t *p_avg, int i_divider )
510 const mtime_t i_tmp = p_avg->i_value * p_avg->i_divider + p_avg->i_residue;
512 p_avg->i_divider = i_divider;
513 p_avg->i_value = i_tmp / p_avg->i_divider;
514 p_avg->i_residue = i_tmp % p_avg->i_divider;