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_GetTS (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( 0, 0 );
169 cl->last = clock_point_Create( 0, 0 );
173 cl->i_next_drift_update = 0;
174 AvgInit( &cl->drift, 10 );
178 cl->b_paused = false;
179 cl->i_pause_date = 0;
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 vlc_mutex_lock( &cl->lock );
208 if( ( !cl->b_has_reference ) ||
209 ( i_ck_stream == 0 && cl->last.i_stream != 0 ) )
212 b_reset_reference= true;
214 else if( cl->last.i_stream != 0 &&
215 ( (cl->last.i_stream - i_ck_stream) > CR_MAX_GAP ||
216 (cl->last.i_stream - i_ck_stream) < -CR_MAX_GAP ) )
218 /* Stream discontinuity, for which we haven't received a
219 * warning from the stream control facilities (dd-edited
221 msg_Warn( p_log, "clock gap, unexpected stream discontinuity" );
225 msg_Warn( p_log, "feeding synchro with a new reference point trying to recover from clock gap" );
226 b_reset_reference= true;
228 if( b_reset_reference )
230 cl->i_next_drift_update = 0;
231 AvgReset( &cl->drift );
233 /* Feed synchro with a new reference point. */
234 cl->b_has_reference = true;
235 cl->ref = clock_point_Create( i_ck_stream,
236 __MAX( cl->i_ts_max + CR_MEAN_PTS_GAP, i_ck_system ) );
239 if( !b_can_pace_control && cl->i_next_drift_update < i_ck_system )
241 const mtime_t i_converted = ClockSystemToStream( cl, i_ck_system );
243 AvgUpdate( &cl->drift, i_converted - i_ck_stream );
245 cl->i_next_drift_update = i_ck_system + CLOCK_FREQ/5; /* FIXME why that */
247 cl->last = clock_point_Create( i_ck_stream, i_ck_system );
249 vlc_mutex_unlock( &cl->lock );
252 /*****************************************************************************
254 *****************************************************************************/
255 void input_clock_Reset( input_clock_t *cl )
257 vlc_mutex_lock( &cl->lock );
259 cl->b_has_reference = false;
260 cl->ref = clock_point_Create( 0, 0 );
263 vlc_mutex_unlock( &cl->lock );
266 /*****************************************************************************
267 * input_clock_ChangeRate:
268 *****************************************************************************/
269 void input_clock_ChangeRate( input_clock_t *cl, int i_rate )
271 vlc_mutex_lock( &cl->lock );
273 /* Move the reference point */
274 if( cl->b_has_reference )
276 cl->last.i_system = ClockStreamToSystem( cl, cl->last.i_stream );
282 vlc_mutex_unlock( &cl->lock );
285 /*****************************************************************************
286 * input_clock_ChangePause:
287 *****************************************************************************/
288 void input_clock_ChangePause( input_clock_t *cl, bool b_paused, mtime_t i_date )
290 vlc_mutex_lock( &cl->lock );
291 assert( (!cl->b_paused) != (!b_paused) );
295 const mtime_t i_duration = i_date - cl->i_pause_date;
297 if( cl->b_has_reference && i_duration > 0 )
299 cl->ref.i_system += i_duration;
300 cl->last.i_system += i_duration;
303 cl->i_pause_date = i_date;
304 cl->b_paused = b_paused;
306 vlc_mutex_unlock( &cl->lock );
309 /*****************************************************************************
310 * input_clock_GetWakeup
311 *****************************************************************************/
312 mtime_t input_clock_GetWakeup( input_clock_t *cl )
314 mtime_t i_wakeup = 0;
316 vlc_mutex_lock( &cl->lock );
318 /* Synchronized, we can wait */
319 if( cl->b_has_reference )
320 i_wakeup = ClockStreamToSystem( cl, cl->last.i_stream );
322 vlc_mutex_unlock( &cl->lock );
327 /*****************************************************************************
328 * input_clock_GetTS: manages a PTS or DTS
329 *****************************************************************************/
330 mtime_t input_clock_GetTS( input_clock_t *cl, int *pi_rate,
331 mtime_t i_ts, mtime_t i_ts_bound )
333 mtime_t i_converted_ts;
335 vlc_mutex_lock( &cl->lock );
338 *pi_rate = cl->i_rate;
340 if( !cl->b_has_reference )
342 vlc_mutex_unlock( &cl->lock );
347 i_converted_ts = ClockStreamToSystem( cl, i_ts + AvgGet( &cl->drift ) );
348 if( i_converted_ts > cl->i_ts_max )
349 cl->i_ts_max = i_converted_ts;
351 vlc_mutex_unlock( &cl->lock );
353 i_converted_ts += cl->i_pts_delay;
355 /* Check ts validity */
356 if( i_ts_bound != INT64_MAX &&
357 i_converted_ts >= mdate() + cl->i_pts_delay + i_ts_bound )
360 return i_converted_ts;
362 /*****************************************************************************
363 * input_clock_GetRate: Return current rate
364 *****************************************************************************/
365 int input_clock_GetRate( input_clock_t *cl )
369 vlc_mutex_lock( &cl->lock );
371 vlc_mutex_unlock( &cl->lock );
376 int input_clock_GetState( input_clock_t *cl,
377 mtime_t *pi_stream_start, mtime_t *pi_system_start,
378 mtime_t *pi_stream_duration, mtime_t *pi_system_duration )
380 vlc_mutex_lock( &cl->lock );
382 if( !cl->b_has_reference )
384 vlc_mutex_unlock( &cl->lock );
388 *pi_stream_start = cl->ref.i_stream;
389 *pi_system_start = cl->ref.i_system;
391 *pi_stream_duration = cl->last.i_stream - cl->ref.i_stream;
392 *pi_system_duration = cl->last.i_system - cl->ref.i_system;
394 vlc_mutex_unlock( &cl->lock );
399 void input_clock_ChangeSystemOrigin( input_clock_t *cl, mtime_t i_system )
401 vlc_mutex_lock( &cl->lock );
403 assert( cl->b_has_reference );
404 const mtime_t i_offset = i_system - cl->ref.i_system;
406 cl->ref.i_system += i_offset;
407 cl->last.i_system += i_offset;
409 vlc_mutex_unlock( &cl->lock );
412 #warning "input_clock_SetJitter needs more work"
413 void input_clock_SetJitter( input_clock_t *cl,
414 mtime_t i_pts_delay, int i_cr_average )
416 vlc_mutex_lock( &cl->lock );
418 /* TODO always save the value, and when rebuffering use the new one if smaller
419 * TODO when increasing -> force rebuffering
421 if( cl->i_pts_delay < i_pts_delay )
422 cl->i_pts_delay = i_pts_delay;
425 if( i_cr_average < 10 )
428 if( cl->drift.i_divider != i_cr_average )
429 AvgRescale( &cl->drift, i_cr_average );
431 vlc_mutex_unlock( &cl->lock );
434 /*****************************************************************************
435 * ClockStreamToSystem: converts a movie clock to system date
436 *****************************************************************************/
437 static mtime_t ClockStreamToSystem( input_clock_t *cl, mtime_t i_stream )
439 if( !cl->b_has_reference )
442 return ( i_stream - cl->ref.i_stream ) * cl->i_rate / INPUT_RATE_DEFAULT +
446 /*****************************************************************************
447 * ClockSystemToStream: converts a system date to movie clock
448 *****************************************************************************
449 * Caution : a valid reference point is needed for this to operate.
450 *****************************************************************************/
451 static mtime_t ClockSystemToStream( input_clock_t *cl, mtime_t i_system )
453 assert( cl->b_has_reference );
454 return ( i_system - cl->ref.i_system ) * INPUT_RATE_DEFAULT / cl->i_rate +
458 /*****************************************************************************
459 * Long term average helpers
460 *****************************************************************************/
461 static void AvgInit( average_t *p_avg, int i_divider )
463 p_avg->i_divider = i_divider;
466 static void AvgClean( average_t *p_avg )
470 static void AvgReset( average_t *p_avg )
473 p_avg->i_residue = 0;
476 static void AvgUpdate( average_t *p_avg, mtime_t i_value )
478 const int i_f0 = __MIN( p_avg->i_divider - 1, p_avg->i_count );
479 const int i_f1 = p_avg->i_divider - i_f0;
481 const mtime_t i_tmp = i_f0 * p_avg->i_value + i_f1 * i_value + p_avg->i_residue;
483 p_avg->i_value = i_tmp / p_avg->i_divider;
484 p_avg->i_residue = i_tmp % p_avg->i_divider;
488 static mtime_t AvgGet( average_t *p_avg )
490 return p_avg->i_value;
492 static void AvgRescale( average_t *p_avg, int i_divider )
494 const mtime_t i_tmp = p_avg->i_value * p_avg->i_divider + p_avg->i_residue;
496 p_avg->i_divider = i_divider;
497 p_avg->i_value = i_tmp / p_avg->i_divider;
498 p_avg->i_residue = i_tmp % p_avg->i_divider;