2 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
3 * 2000 Wim Taymans <wtay@chello.be>
4 * 2004 Wim Taymans <wim@fluendo.com>
6 * gstclock.c: Clock subsystem for maintaining time sync
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Library General Public
10 * License as published by the Free Software Foundation; either
11 * version 2 of the License, or (at your option) any later version.
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Library General Public License for more details.
18 * You should have received a copy of the GNU Library General Public
19 * License along with this library; if not, write to the
20 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
21 * Boston, MA 02111-1307, USA.
26 * @short_description: Abstract class for global clocks
27 * @see_also: #GstSystemClock, #GstPipeline
29 * GStreamer uses a global clock to synchronize the plugins in a pipeline.
30 * Different clock implementations are possible by implementing this abstract
31 * base class or, more conveniently, by subclassing #GstSystemClock.
33 * The #GstClock returns a monotonically increasing time with the method
34 * gst_clock_get_time(). Its accuracy and base time depend on the specific
35 * clock implementation but time is always expressed in nanoseconds. Since the
36 * baseline of the clock is undefined, the clock time returned is not
37 * meaningful in itself, what matters are the deltas between two clock times.
38 * The time returned by a clock is called the absolute time.
40 * The pipeline uses the clock to calculate the running time. Usually all
41 * renderers synchronize to the global clock using the buffer timestamps, the
42 * newsegment events and the element's base time, see #GstPipeline.
44 * A clock implementation can support periodic and single shot clock
45 * notifications both synchronous and asynchronous.
47 * One first needs to create a #GstClockID for the periodic or single shot
48 * notification using gst_clock_new_single_shot_id() or
49 * gst_clock_new_periodic_id().
51 * To perform a blocking wait for the specific time of the #GstClockID use the
52 * gst_clock_id_wait(). To receive a callback when the specific time is reached
53 * in the clock use gst_clock_id_wait_async(). Both these calls can be
54 * interrupted with the gst_clock_id_unschedule() call. If the blocking wait is
55 * unscheduled a return value of #GST_CLOCK_UNSCHEDULED is returned.
57 * Periodic callbacks scheduled async will be repeatedly called automatically
58 * until it is unscheduled. To schedule a sync periodic callback,
59 * gst_clock_id_wait() should be called repeatedly.
61 * The async callbacks can happen from any thread, either provided by the core
62 * or from a streaming thread. The application should be prepared for this.
64 * A #GstClockID that has been unscheduled cannot be used again for any wait
65 * operation, a new #GstClockID should be created and the old unscheduled one
66 * should be destroyed with gst_clock_id_unref().
68 * It is possible to perform a blocking wait on the same #GstClockID from
69 * multiple threads. However, registering the same #GstClockID for multiple
70 * async notifications is not possible, the callback will only be called for
71 * the thread registering the entry last.
73 * None of the wait operations unref the #GstClockID, the owner is responsible
74 * for unreffing the ids itself. This holds for both periodic and single shot
75 * notifications. The reason being that the owner of the #GstClockID has to
76 * keep a handle to the #GstClockID to unblock the wait on FLUSHING events or
77 * state changes and if the entry would be unreffed automatically, the handle
78 * might become invalid without any notification.
80 * These clock operations do not operate on the running time, so the callbacks
81 * will also occur when not in PLAYING state as if the clock just keeps on
82 * running. Some clocks however do not progress when the element that provided
83 * the clock is not PLAYING.
85 * When a clock has the #GST_CLOCK_FLAG_CAN_SET_MASTER flag set, it can be
86 * slaved to another #GstClock with the gst_clock_set_master(). The clock will
87 * then automatically be synchronized to this master clock by repeatedly
88 * sampling the master clock and the slave clock and recalibrating the slave
89 * clock with gst_clock_set_calibration(). This feature is mostly useful for
90 * plugins that have an internal clock but must operate with another clock
91 * selected by the #GstPipeline. They can track the offset and rate difference
92 * of their internal clock relative to the master clock by using the
93 * gst_clock_get_calibration() function.
95 * The master/slave synchronisation can be tuned with the #GstClock:timeout,
96 * #GstClock:window-size and #GstClock:window-threshold properties.
97 * The #GstClock:timeout property defines the interval to sample the master
98 * clock and run the calibration functions. #GstClock:window-size defines the
99 * number of samples to use when calibrating and #GstClock:window-threshold
100 * defines the minimum number of samples before the calibration is performed.
102 * Last reviewed on 2012-03-28 (0.11.3)
106 #include "gst_private.h"
109 #include "gstclock.h"
111 #include "gstutils.h"
112 #include "glib-compat-private.h"
114 #ifndef GST_DISABLE_TRACE
115 /* #define GST_WITH_ALLOC_TRACE */
116 #include "gsttrace.h"
117 static GstAllocTrace *_gst_clock_entry_trace;
120 /* #define DEBUGGING_ENABLED */
122 #define DEFAULT_WINDOW_SIZE 32
123 #define DEFAULT_WINDOW_THRESHOLD 4
124 #define DEFAULT_TIMEOUT GST_SECOND / 10
130 PROP_WINDOW_THRESHOLD,
134 #define GST_CLOCK_SLAVE_LOCK(clock) g_mutex_lock (&GST_CLOCK_CAST (clock)->priv->slave_lock)
135 #define GST_CLOCK_SLAVE_UNLOCK(clock) g_mutex_unlock (&GST_CLOCK_CAST (clock)->priv->slave_lock)
137 struct _GstClockPrivate
139 GMutex slave_lock; /* order: SLAVE_LOCK, OBJECT_LOCK */
142 GstClockTime internal_calibration;
143 GstClockTime external_calibration;
144 GstClockTime rate_numerator;
145 GstClockTime rate_denominator;
146 GstClockTime last_time;
149 GstClockTime resolution;
151 /* for master/slave clocks */
154 /* with SLAVE_LOCK */
157 gint window_threshold;
159 GstClockTime timeout;
168 #define read_seqbegin(clock) \
169 g_atomic_int_get (&clock->priv->post_count);
171 static inline gboolean
172 read_seqretry (GstClock * clock, gint seq)
174 /* no retry if the seqnum did not change */
175 if (G_LIKELY (seq == g_atomic_int_get (&clock->priv->pre_count)))
178 /* wait for the writer to finish and retry */
179 GST_OBJECT_LOCK (clock);
180 GST_OBJECT_UNLOCK (clock);
184 #define write_seqlock(clock) \
186 GST_OBJECT_LOCK (clock); \
187 g_atomic_int_inc (&clock->priv->pre_count); \
190 #define write_sequnlock(clock) \
192 g_atomic_int_inc (&clock->priv->post_count); \
193 GST_OBJECT_UNLOCK (clock); \
196 static void gst_clock_dispose (GObject * object);
197 static void gst_clock_finalize (GObject * object);
199 static void gst_clock_set_property (GObject * object, guint prop_id,
200 const GValue * value, GParamSpec * pspec);
201 static void gst_clock_get_property (GObject * object, guint prop_id,
202 GValue * value, GParamSpec * pspec);
204 /* static guint gst_clock_signals[LAST_SIGNAL] = { 0 }; */
207 gst_clock_entry_new (GstClock * clock, GstClockTime time,
208 GstClockTime interval, GstClockEntryType type)
210 GstClockEntry *entry;
212 entry = g_slice_new (GstClockEntry);
213 #ifndef GST_DISABLE_TRACE
214 _gst_alloc_trace_new (_gst_clock_entry_trace, entry);
216 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
217 "created entry %p, time %" GST_TIME_FORMAT, entry, GST_TIME_ARGS (time));
220 entry->clock = clock;
223 entry->interval = interval;
224 entry->status = GST_CLOCK_OK;
226 entry->user_data = NULL;
227 entry->destroy_data = NULL;
228 entry->unscheduled = FALSE;
229 entry->woken_up = FALSE;
231 return (GstClockID) entry;
234 /* WARNING : Does not modify the refcount
235 * WARNING : Do not use if a pending clock operation is happening on that entry */
237 gst_clock_entry_reinit (GstClock * clock, GstClockEntry * entry,
238 GstClockTime time, GstClockTime interval, GstClockEntryType type)
240 g_return_val_if_fail (entry->status != GST_CLOCK_BUSY, FALSE);
241 g_return_val_if_fail (entry->clock == clock, FALSE);
245 entry->interval = interval;
246 entry->status = GST_CLOCK_OK;
247 entry->unscheduled = FALSE;
248 entry->woken_up = FALSE;
254 * gst_clock_single_shot_id_reinit:
255 * @clock: a #GstClock
257 * @time: The requested time.
259 * Reinitializes the provided single shot @id to the provided time. Does not
260 * modify the reference count.
262 * Returns: %TRUE if the GstClockID could be reinitialized to the provided
263 * @time, else %FALSE.
268 gst_clock_single_shot_id_reinit (GstClock * clock, GstClockID id,
271 return gst_clock_entry_reinit (clock, (GstClockEntry *) id, time,
272 GST_CLOCK_TIME_NONE, GST_CLOCK_ENTRY_SINGLE);
276 * gst_clock_periodic_id_reinit:
277 * @clock: a #GstClock
279 * @start_time: the requested start time
280 * @interval: the requested interval
282 * Reinitializes the provided periodic @id to the provided start time and
283 * interval. Does not modify the reference count.
285 * Returns: %TRUE if the GstClockID could be reinitialized to the provided
286 * @time, else %FALSE.
292 gst_clock_periodic_id_reinit (GstClock * clock, GstClockID id,
293 GstClockTime start_time, GstClockTime interval)
295 return gst_clock_entry_reinit (clock, (GstClockEntry *) id, start_time,
296 interval, GST_CLOCK_ENTRY_PERIODIC);
301 * @id: The #GstClockID to ref
303 * Increase the refcount of given @id.
305 * Returns: (transfer full): The same #GstClockID with increased refcount.
310 gst_clock_id_ref (GstClockID id)
312 g_return_val_if_fail (id != NULL, NULL);
314 g_atomic_int_inc (&((GstClockEntry *) id)->refcount);
320 _gst_clock_id_free (GstClockID id)
322 GstClockEntry *entry;
323 g_return_if_fail (id != NULL);
325 GST_CAT_DEBUG (GST_CAT_CLOCK, "freed entry %p", id);
326 entry = (GstClockEntry *) id;
327 if (entry->destroy_data)
328 entry->destroy_data (entry->user_data);
330 #ifndef GST_DISABLE_TRACE
331 _gst_alloc_trace_free (_gst_clock_entry_trace, id);
333 g_slice_free (GstClockEntry, id);
337 * gst_clock_id_unref:
338 * @id: (transfer full): The #GstClockID to unref
340 * Unref given @id. When the refcount reaches 0 the
341 * #GstClockID will be freed.
346 gst_clock_id_unref (GstClockID id)
350 g_return_if_fail (id != NULL);
352 zero = g_atomic_int_dec_and_test (&((GstClockEntry *) id)->refcount);
353 /* if we ended up with the refcount at zero, free the id */
355 _gst_clock_id_free (id);
360 * gst_clock_new_single_shot_id:
361 * @clock: The #GstClockID to get a single shot notification from
362 * @time: the requested time
364 * Get a #GstClockID from @clock to trigger a single shot
365 * notification at the requested time. The single shot id should be
366 * unreffed after usage.
368 * Free-function: gst_clock_id_unref
370 * Returns: (transfer full): a #GstClockID that can be used to request the
376 gst_clock_new_single_shot_id (GstClock * clock, GstClockTime time)
378 g_return_val_if_fail (GST_IS_CLOCK (clock), NULL);
380 return gst_clock_entry_new (clock,
381 time, GST_CLOCK_TIME_NONE, GST_CLOCK_ENTRY_SINGLE);
385 * gst_clock_new_periodic_id:
386 * @clock: The #GstClockID to get a periodic notification id from
387 * @start_time: the requested start time
388 * @interval: the requested interval
390 * Get an ID from @clock to trigger a periodic notification.
391 * The periodic notifications will start at time @start_time and
392 * will then be fired with the given @interval. @id should be unreffed
395 * Free-function: gst_clock_id_unref
397 * Returns: (transfer full): a #GstClockID that can be used to request the
403 gst_clock_new_periodic_id (GstClock * clock, GstClockTime start_time,
404 GstClockTime interval)
406 g_return_val_if_fail (GST_IS_CLOCK (clock), NULL);
407 g_return_val_if_fail (GST_CLOCK_TIME_IS_VALID (start_time), NULL);
408 g_return_val_if_fail (interval != 0, NULL);
409 g_return_val_if_fail (GST_CLOCK_TIME_IS_VALID (interval), NULL);
411 return gst_clock_entry_new (clock,
412 start_time, interval, GST_CLOCK_ENTRY_PERIODIC);
416 * gst_clock_id_compare_func:
417 * @id1: A #GstClockID
418 * @id2: A #GstClockID to compare with
420 * Compares the two #GstClockID instances. This function can be used
421 * as a GCompareFunc when sorting ids.
423 * Returns: negative value if a < b; zero if a = b; positive value if a > b
428 gst_clock_id_compare_func (gconstpointer id1, gconstpointer id2)
430 GstClockEntry *entry1, *entry2;
432 entry1 = (GstClockEntry *) id1;
433 entry2 = (GstClockEntry *) id2;
435 if (GST_CLOCK_ENTRY_TIME (entry1) > GST_CLOCK_ENTRY_TIME (entry2)) {
438 if (GST_CLOCK_ENTRY_TIME (entry1) < GST_CLOCK_ENTRY_TIME (entry2)) {
445 * gst_clock_id_get_time:
446 * @id: The #GstClockID to query
448 * Get the time of the clock ID
450 * Returns: the time of the given clock id.
455 gst_clock_id_get_time (GstClockID id)
457 g_return_val_if_fail (id != NULL, GST_CLOCK_TIME_NONE);
459 return GST_CLOCK_ENTRY_TIME ((GstClockEntry *) id);
464 * @id: The #GstClockID to wait on
465 * @jitter: (out) (allow-none): a pointer that will contain the jitter,
468 * Perform a blocking wait on @id.
469 * @id should have been created with gst_clock_new_single_shot_id()
470 * or gst_clock_new_periodic_id() and should not have been unscheduled
471 * with a call to gst_clock_id_unschedule().
473 * If the @jitter argument is not %NULL and this function returns #GST_CLOCK_OK
474 * or #GST_CLOCK_EARLY, it will contain the difference
475 * against the clock and the time of @id when this method was
477 * Positive values indicate how late @id was relative to the clock
478 * (in which case this function will return #GST_CLOCK_EARLY).
479 * Negative values indicate how much time was spent waiting on the clock
480 * before this function returned.
482 * Returns: the result of the blocking wait. #GST_CLOCK_EARLY will be returned
483 * if the current clock time is past the time of @id, #GST_CLOCK_OK if
484 * @id was scheduled in time. #GST_CLOCK_UNSCHEDULED if @id was
485 * unscheduled with gst_clock_id_unschedule().
490 gst_clock_id_wait (GstClockID id, GstClockTimeDiff * jitter)
492 GstClockEntry *entry;
495 GstClockTime requested;
496 GstClockClass *cclass;
498 g_return_val_if_fail (id != NULL, GST_CLOCK_ERROR);
500 entry = (GstClockEntry *) id;
501 requested = GST_CLOCK_ENTRY_TIME (entry);
503 clock = GST_CLOCK_ENTRY_CLOCK (entry);
505 /* can't sync on invalid times */
506 if (G_UNLIKELY (!GST_CLOCK_TIME_IS_VALID (requested)))
509 cclass = GST_CLOCK_GET_CLASS (clock);
511 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "waiting on clock entry %p", id);
513 /* if we have a wait_jitter function, use that */
514 if (G_UNLIKELY (cclass->wait == NULL))
517 res = cclass->wait (clock, entry, jitter);
519 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
520 "done waiting entry %p, res: %d", id, res);
522 if (entry->type == GST_CLOCK_ENTRY_PERIODIC)
523 entry->time = requested + entry->interval;
530 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
531 "invalid time requested, returning _BADTIME");
532 return GST_CLOCK_BADTIME;
536 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "clock wait is not supported");
537 return GST_CLOCK_UNSUPPORTED;
542 * gst_clock_id_wait_async:
543 * @id: a #GstClockID to wait on
544 * @func: The callback function
545 * @user_data: User data passed in the callback
546 * @destroy_data: #GDestroyNotify for user_data
548 * Register a callback on the given #GstClockID @id with the given
549 * function and user_data. When passing a #GstClockID with an invalid
550 * time to this function, the callback will be called immediately
551 * with a time set to GST_CLOCK_TIME_NONE. The callback will
552 * be called when the time of @id has been reached.
554 * The callback @func can be invoked from any thread, either provided by the
555 * core or from a streaming thread. The application should be prepared for this.
557 * Returns: the result of the non blocking wait.
564 gst_clock_id_wait_async (GstClockID id,
565 GstClockCallback func, gpointer user_data, GDestroyNotify destroy_data)
567 GstClockEntry *entry;
570 GstClockClass *cclass;
571 GstClockTime requested;
573 g_return_val_if_fail (id != NULL, GST_CLOCK_ERROR);
574 g_return_val_if_fail (func != NULL, GST_CLOCK_ERROR);
576 entry = (GstClockEntry *) id;
577 requested = GST_CLOCK_ENTRY_TIME (entry);
578 clock = GST_CLOCK_ENTRY_CLOCK (entry);
580 /* can't sync on invalid times */
581 if (G_UNLIKELY (!GST_CLOCK_TIME_IS_VALID (requested)))
584 cclass = GST_CLOCK_GET_CLASS (clock);
586 if (G_UNLIKELY (cclass->wait_async == NULL))
590 entry->user_data = user_data;
591 entry->destroy_data = destroy_data;
593 res = cclass->wait_async (clock, entry);
600 (func) (clock, GST_CLOCK_TIME_NONE, id, user_data);
601 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
602 "invalid time requested, returning _BADTIME");
603 return GST_CLOCK_BADTIME;
607 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "clock wait is not supported");
608 return GST_CLOCK_UNSUPPORTED;
613 * gst_clock_id_unschedule:
614 * @id: The id to unschedule
616 * Cancel an outstanding request with @id. This can either
617 * be an outstanding async notification or a pending sync notification.
618 * After this call, @id cannot be used anymore to receive sync or
619 * async notifications, you need to create a new #GstClockID.
624 gst_clock_id_unschedule (GstClockID id)
626 GstClockEntry *entry;
628 GstClockClass *cclass;
630 g_return_if_fail (id != NULL);
632 entry = (GstClockEntry *) id;
633 clock = entry->clock;
635 cclass = GST_CLOCK_GET_CLASS (clock);
637 if (G_LIKELY (cclass->unschedule))
638 cclass->unschedule (clock, entry);
643 * GstClock abstract base class implementation
645 #define gst_clock_parent_class parent_class
646 G_DEFINE_TYPE (GstClock, gst_clock, GST_TYPE_OBJECT);
649 gst_clock_class_init (GstClockClass * klass)
651 GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
653 #ifndef GST_DISABLE_TRACE
654 _gst_clock_entry_trace = _gst_alloc_trace_register ("GstClockEntry", -1);
657 gobject_class->dispose = gst_clock_dispose;
658 gobject_class->finalize = gst_clock_finalize;
659 gobject_class->set_property = gst_clock_set_property;
660 gobject_class->get_property = gst_clock_get_property;
662 g_object_class_install_property (gobject_class, PROP_WINDOW_SIZE,
663 g_param_spec_int ("window-size", "Window size",
664 "The size of the window used to calculate rate and offset", 2, 1024,
665 DEFAULT_WINDOW_SIZE, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
666 g_object_class_install_property (gobject_class, PROP_WINDOW_THRESHOLD,
667 g_param_spec_int ("window-threshold", "Window threshold",
668 "The threshold to start calculating rate and offset", 2, 1024,
669 DEFAULT_WINDOW_THRESHOLD,
670 G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
671 g_object_class_install_property (gobject_class, PROP_TIMEOUT,
672 g_param_spec_uint64 ("timeout", "Timeout",
673 "The amount of time, in nanoseconds, to sample master and slave clocks",
674 0, G_MAXUINT64, DEFAULT_TIMEOUT,
675 G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
677 g_type_class_add_private (klass, sizeof (GstClockPrivate));
681 gst_clock_init (GstClock * clock)
683 GstClockPrivate *priv;
686 G_TYPE_INSTANCE_GET_PRIVATE (clock, GST_TYPE_CLOCK, GstClockPrivate);
690 priv->internal_calibration = 0;
691 priv->external_calibration = 0;
692 priv->rate_numerator = 1;
693 priv->rate_denominator = 1;
695 g_mutex_init (&priv->slave_lock);
696 priv->window_size = DEFAULT_WINDOW_SIZE;
697 priv->window_threshold = DEFAULT_WINDOW_THRESHOLD;
698 priv->filling = TRUE;
699 priv->time_index = 0;
700 priv->timeout = DEFAULT_TIMEOUT;
701 priv->times = g_new0 (GstClockTime, 4 * priv->window_size);
705 gst_clock_dispose (GObject * object)
707 GstClock *clock = GST_CLOCK (object);
710 GST_OBJECT_LOCK (clock);
711 master_p = &clock->priv->master;
712 gst_object_replace ((GstObject **) master_p, NULL);
713 GST_OBJECT_UNLOCK (clock);
715 G_OBJECT_CLASS (parent_class)->dispose (object);
719 gst_clock_finalize (GObject * object)
721 GstClock *clock = GST_CLOCK (object);
723 GST_CLOCK_SLAVE_LOCK (clock);
724 if (clock->priv->clockid) {
725 gst_clock_id_unschedule (clock->priv->clockid);
726 gst_clock_id_unref (clock->priv->clockid);
727 clock->priv->clockid = NULL;
729 g_free (clock->priv->times);
730 clock->priv->times = NULL;
731 GST_CLOCK_SLAVE_UNLOCK (clock);
733 g_mutex_clear (&clock->priv->slave_lock);
735 G_OBJECT_CLASS (parent_class)->finalize (object);
739 * gst_clock_set_resolution:
740 * @clock: a #GstClock
741 * @resolution: The resolution to set
743 * Set the accuracy of the clock. Some clocks have the possibility to operate
744 * with different accuracy at the expense of more resource usage. There is
745 * normally no need to change the default resolution of a clock. The resolution
746 * of a clock can only be changed if the clock has the
747 * #GST_CLOCK_FLAG_CAN_SET_RESOLUTION flag set.
749 * Returns: the new resolution of the clock.
752 gst_clock_set_resolution (GstClock * clock, GstClockTime resolution)
754 GstClockPrivate *priv;
755 GstClockClass *cclass;
757 g_return_val_if_fail (GST_IS_CLOCK (clock), 0);
758 g_return_val_if_fail (resolution != 0, 0);
760 cclass = GST_CLOCK_GET_CLASS (clock);
763 if (cclass->change_resolution)
765 cclass->change_resolution (clock, priv->resolution, resolution);
767 return priv->resolution;
771 * gst_clock_get_resolution:
772 * @clock: a #GstClock
774 * Get the accuracy of the clock. The accuracy of the clock is the granularity
775 * of the values returned by gst_clock_get_time().
777 * Returns: the resolution of the clock in units of #GstClockTime.
782 gst_clock_get_resolution (GstClock * clock)
784 GstClockClass *cclass;
786 g_return_val_if_fail (GST_IS_CLOCK (clock), 0);
788 cclass = GST_CLOCK_GET_CLASS (clock);
790 if (cclass->get_resolution)
791 return cclass->get_resolution (clock);
797 * gst_clock_adjust_unlocked:
798 * @clock: a #GstClock to use
799 * @internal: a clock time
801 * Converts the given @internal clock time to the external time, adjusting for the
802 * rate and reference time set with gst_clock_set_calibration() and making sure
803 * that the returned time is increasing. This function should be called with the
804 * clock's OBJECT_LOCK held and is mainly used by clock subclasses.
806 * This function is the reverse of gst_clock_unadjust_unlocked().
808 * Returns: the converted time of the clock.
811 gst_clock_adjust_unlocked (GstClock * clock, GstClockTime internal)
813 GstClockTime ret, cinternal, cexternal, cnum, cdenom;
814 GstClockPrivate *priv = clock->priv;
816 /* get calibration values for readability */
817 cinternal = priv->internal_calibration;
818 cexternal = priv->external_calibration;
819 cnum = priv->rate_numerator;
820 cdenom = priv->rate_denominator;
822 /* avoid divide by 0 */
823 if (G_UNLIKELY (cdenom == 0))
826 /* The formula is (internal - cinternal) * cnum / cdenom + cexternal
828 * Since we do math on unsigned 64-bit ints we have to special case for
829 * internal < cinternal to get the sign right. this case is not very common,
832 if (G_LIKELY (internal >= cinternal)) {
833 ret = internal - cinternal;
834 ret = gst_util_uint64_scale (ret, cnum, cdenom);
837 ret = cinternal - internal;
838 ret = gst_util_uint64_scale (ret, cnum, cdenom);
840 if (G_LIKELY (cexternal > ret))
841 ret = cexternal - ret;
846 /* make sure the time is increasing */
847 priv->last_time = MAX (ret, priv->last_time);
849 return priv->last_time;
853 * gst_clock_unadjust_unlocked:
854 * @clock: a #GstClock to use
855 * @external: an external clock time
857 * Converts the given @external clock time to the internal time of @clock,
858 * using the rate and reference time set with gst_clock_set_calibration().
859 * This function should be called with the clock's OBJECT_LOCK held and
860 * is mainly used by clock subclasses.
862 * This function is the reverse of gst_clock_adjust_unlocked().
864 * Returns: the internal time of the clock corresponding to @external.
869 gst_clock_unadjust_unlocked (GstClock * clock, GstClockTime external)
871 GstClockTime ret, cinternal, cexternal, cnum, cdenom;
872 GstClockPrivate *priv = clock->priv;
874 /* get calibration values for readability */
875 cinternal = priv->internal_calibration;
876 cexternal = priv->external_calibration;
877 cnum = priv->rate_numerator;
878 cdenom = priv->rate_denominator;
880 /* avoid divide by 0 */
881 if (G_UNLIKELY (cnum == 0))
884 /* The formula is (external - cexternal) * cdenom / cnum + cinternal */
885 if (G_LIKELY (external >= cexternal)) {
886 ret = external - cexternal;
887 ret = gst_util_uint64_scale (ret, cdenom, cnum);
890 ret = cexternal - external;
891 ret = gst_util_uint64_scale (ret, cdenom, cnum);
892 if (G_LIKELY (cinternal > ret))
893 ret = cinternal - ret;
901 * gst_clock_get_internal_time:
902 * @clock: a #GstClock to query
904 * Gets the current internal time of the given clock. The time is returned
905 * unadjusted for the offset and the rate.
907 * Returns: the internal time of the clock. Or GST_CLOCK_TIME_NONE when
908 * given invalid input.
913 gst_clock_get_internal_time (GstClock * clock)
916 GstClockClass *cclass;
918 g_return_val_if_fail (GST_IS_CLOCK (clock), GST_CLOCK_TIME_NONE);
920 cclass = GST_CLOCK_GET_CLASS (clock);
922 if (G_UNLIKELY (cclass->get_internal_time == NULL))
925 ret = cclass->get_internal_time (clock);
927 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "internal time %" GST_TIME_FORMAT,
928 GST_TIME_ARGS (ret));
935 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
936 "internal time not supported, return 0");
937 return G_GINT64_CONSTANT (0);
942 * gst_clock_get_time:
943 * @clock: a #GstClock to query
945 * Gets the current time of the given clock. The time is always
946 * monotonically increasing and adjusted according to the current
949 * Returns: the time of the clock. Or GST_CLOCK_TIME_NONE when
950 * given invalid input.
955 gst_clock_get_time (GstClock * clock)
960 g_return_val_if_fail (GST_IS_CLOCK (clock), GST_CLOCK_TIME_NONE);
963 /* reget the internal time when we retry to get the most current
965 ret = gst_clock_get_internal_time (clock);
967 seq = read_seqbegin (clock);
968 /* this will scale for rate and offset */
969 ret = gst_clock_adjust_unlocked (clock, ret);
970 } while (read_seqretry (clock, seq));
972 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "adjusted time %" GST_TIME_FORMAT,
973 GST_TIME_ARGS (ret));
979 * gst_clock_set_calibration:
980 * @clock: a #GstClock to calibrate
981 * @internal: a reference internal time
982 * @external: a reference external time
983 * @rate_num: the numerator of the rate of the clock relative to its
985 * @rate_denom: the denominator of the rate of the clock
987 * Adjusts the rate and time of @clock. A rate of 1/1 is the normal speed of
988 * the clock. Values bigger than 1/1 make the clock go faster.
990 * @internal and @external are calibration parameters that arrange that
991 * gst_clock_get_time() should have been @external at internal time @internal.
992 * This internal time should not be in the future; that is, it should be less
993 * than the value of gst_clock_get_internal_time() when this function is called.
995 * Subsequent calls to gst_clock_get_time() will return clock times computed as
999 * time = (internal_time - internal) * rate_num / rate_denom + external
1002 * This formula is implemented in gst_clock_adjust_unlocked(). Of course, it
1003 * tries to do the integer arithmetic as precisely as possible.
1005 * Note that gst_clock_get_time() always returns increasing values so when you
1006 * move the clock backwards, gst_clock_get_time() will report the previous value
1007 * until the clock catches up.
1012 gst_clock_set_calibration (GstClock * clock, GstClockTime internal, GstClockTime
1013 external, GstClockTime rate_num, GstClockTime rate_denom)
1015 GstClockPrivate *priv;
1017 g_return_if_fail (GST_IS_CLOCK (clock));
1018 g_return_if_fail (rate_num != GST_CLOCK_TIME_NONE);
1019 g_return_if_fail (rate_denom > 0 && rate_denom != GST_CLOCK_TIME_NONE);
1023 write_seqlock (clock);
1024 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
1025 "internal %" GST_TIME_FORMAT " external %" GST_TIME_FORMAT " %"
1026 G_GUINT64_FORMAT "/%" G_GUINT64_FORMAT " = %f", GST_TIME_ARGS (internal),
1027 GST_TIME_ARGS (external), rate_num, rate_denom,
1028 gst_guint64_to_gdouble (rate_num) / gst_guint64_to_gdouble (rate_denom));
1030 priv->internal_calibration = internal;
1031 priv->external_calibration = external;
1032 priv->rate_numerator = rate_num;
1033 priv->rate_denominator = rate_denom;
1034 write_sequnlock (clock);
1038 * gst_clock_get_calibration:
1039 * @clock: a #GstClock
1040 * @internal: (out) (allow-none): a location to store the internal time
1041 * @external: (out) (allow-none): a location to store the external time
1042 * @rate_num: (out) (allow-none): a location to store the rate numerator
1043 * @rate_denom: (out) (allow-none): a location to store the rate denominator
1045 * Gets the internal rate and reference time of @clock. See
1046 * gst_clock_set_calibration() for more information.
1048 * @internal, @external, @rate_num, and @rate_denom can be left %NULL if the
1049 * caller is not interested in the values.
1054 gst_clock_get_calibration (GstClock * clock, GstClockTime * internal,
1055 GstClockTime * external, GstClockTime * rate_num, GstClockTime * rate_denom)
1058 GstClockPrivate *priv;
1060 g_return_if_fail (GST_IS_CLOCK (clock));
1065 seq = read_seqbegin (clock);
1067 *rate_num = priv->rate_numerator;
1069 *rate_denom = priv->rate_denominator;
1071 *external = priv->external_calibration;
1073 *internal = priv->internal_calibration;
1074 } while (read_seqretry (clock, seq));
1077 /* will be called repeatedly to sample the master and slave clock
1078 * to recalibrate the clock */
1080 gst_clock_slave_callback (GstClock * master, GstClockTime time,
1081 GstClockID id, GstClock * clock)
1083 GstClockTime stime, mtime;
1086 stime = gst_clock_get_internal_time (clock);
1087 mtime = gst_clock_get_time (master);
1089 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
1090 "master %" GST_TIME_FORMAT ", slave %" GST_TIME_FORMAT,
1091 GST_TIME_ARGS (mtime), GST_TIME_ARGS (stime));
1093 gst_clock_add_observation (clock, stime, mtime, &r_squared);
1095 /* FIXME, we can use the r_squared value to adjust the timeout
1096 * value of the clockid */
1102 * gst_clock_set_master:
1103 * @clock: a #GstClock
1104 * @master: (allow-none): a master #GstClock
1106 * Set @master as the master clock for @clock. @clock will be automatically
1107 * calibrated so that gst_clock_get_time() reports the same time as the
1110 * A clock provider that slaves its clock to a master can get the current
1111 * calibration values with gst_clock_get_calibration().
1113 * @master can be %NULL in which case @clock will not be slaved anymore. It will
1114 * however keep reporting its time adjusted with the last configured rate
1117 * Returns: %TRUE if the clock is capable of being slaved to a master clock.
1118 * Trying to set a master on a clock without the
1119 * #GST_CLOCK_FLAG_CAN_SET_MASTER flag will make this function return %FALSE.
1124 gst_clock_set_master (GstClock * clock, GstClock * master)
1126 GstClock **master_p;
1127 GstClockPrivate *priv;
1129 g_return_val_if_fail (GST_IS_CLOCK (clock), FALSE);
1130 g_return_val_if_fail (master != clock, FALSE);
1132 GST_OBJECT_LOCK (clock);
1133 /* we always allow setting the master to NULL */
1134 if (master && !GST_OBJECT_FLAG_IS_SET (clock, GST_CLOCK_FLAG_CAN_SET_MASTER))
1136 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
1137 "slaving %p to master clock %p", clock, master);
1138 GST_OBJECT_UNLOCK (clock);
1142 GST_CLOCK_SLAVE_LOCK (clock);
1143 if (priv->clockid) {
1144 gst_clock_id_unschedule (priv->clockid);
1145 gst_clock_id_unref (priv->clockid);
1146 priv->clockid = NULL;
1149 priv->filling = TRUE;
1150 priv->time_index = 0;
1151 /* use the master periodic id to schedule sampling and
1152 * clock calibration. */
1153 priv->clockid = gst_clock_new_periodic_id (master,
1154 gst_clock_get_time (master), priv->timeout);
1155 gst_clock_id_wait_async (priv->clockid,
1156 (GstClockCallback) gst_clock_slave_callback,
1157 gst_object_ref (clock), (GDestroyNotify) gst_object_unref);
1159 GST_CLOCK_SLAVE_UNLOCK (clock);
1161 GST_OBJECT_LOCK (clock);
1162 master_p = &priv->master;
1163 gst_object_replace ((GstObject **) master_p, (GstObject *) master);
1164 GST_OBJECT_UNLOCK (clock);
1171 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
1172 "cannot be slaved to a master clock");
1173 GST_OBJECT_UNLOCK (clock);
1179 * gst_clock_get_master:
1180 * @clock: a #GstClock
1182 * Get the master clock that @clock is slaved to or %NULL when the clock is
1183 * not slaved to any master clock.
1185 * Returns: (transfer full): a master #GstClock or %NULL when this clock is
1186 * not slaved to a master clock. Unref after usage.
1191 gst_clock_get_master (GstClock * clock)
1193 GstClock *result = NULL;
1194 GstClockPrivate *priv;
1196 g_return_val_if_fail (GST_IS_CLOCK (clock), NULL);
1200 GST_OBJECT_LOCK (clock);
1202 result = gst_object_ref (priv->master);
1203 GST_OBJECT_UNLOCK (clock);
1208 /* http://mathworld.wolfram.com/LeastSquaresFitting.html
1212 do_linear_regression (GstClock * clock, GstClockTime * m_num,
1213 GstClockTime * m_denom, GstClockTime * b, GstClockTime * xbase,
1214 gdouble * r_squared)
1216 GstClockTime *newx, *newy;
1217 GstClockTime xmin, ymin, xbar, ybar, xbar4, ybar4;
1218 GstClockTimeDiff sxx, sxy, syy;
1219 GstClockTime *x, *y;
1222 GstClockPrivate *priv;
1224 xbar = ybar = sxx = syy = sxy = 0;
1229 y = priv->times + 2;
1230 n = priv->filling ? priv->time_index : priv->window_size;
1232 #ifdef DEBUGGING_ENABLED
1233 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "doing regression on:");
1234 for (i = j = 0; i < n; i++, j += 4)
1235 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
1236 " %" G_GUINT64_FORMAT " %" G_GUINT64_FORMAT, x[j], y[j]);
1239 xmin = ymin = G_MAXUINT64;
1240 for (i = j = 0; i < n; i++, j += 4) {
1241 xmin = MIN (xmin, x[j]);
1242 ymin = MIN (ymin, y[j]);
1245 #ifdef DEBUGGING_ENABLED
1246 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "min x: %" G_GUINT64_FORMAT,
1248 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "min y: %" G_GUINT64_FORMAT,
1252 newx = priv->times + 1;
1253 newy = priv->times + 3;
1255 /* strip off unnecessary bits of precision */
1256 for (i = j = 0; i < n; i++, j += 4) {
1257 newx[j] = x[j] - xmin;
1258 newy[j] = y[j] - ymin;
1261 #ifdef DEBUGGING_ENABLED
1262 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "reduced numbers:");
1263 for (i = j = 0; i < n; i++, j += 4)
1264 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
1265 " %" G_GUINT64_FORMAT " %" G_GUINT64_FORMAT, newx[j], newy[j]);
1268 /* have to do this precisely otherwise the results are pretty much useless.
1269 * should guarantee that none of these accumulators can overflow */
1271 /* quantities on the order of 1e10 -> 30 bits; window size a max of 2^10, so
1272 this addition could end up around 2^40 or so -- ample headroom */
1273 for (i = j = 0; i < n; i++, j += 4) {
1280 #ifdef DEBUGGING_ENABLED
1281 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, " xbar = %" G_GUINT64_FORMAT,
1283 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, " ybar = %" G_GUINT64_FORMAT,
1287 /* multiplying directly would give quantities on the order of 1e20 -> 60 bits;
1288 times the window size that's 70 which is too much. Instead we (1) subtract
1289 off the xbar*ybar in the loop instead of after, to avoid accumulation; (2)
1290 shift off 4 bits from each multiplicand, giving an expected ceiling of 52
1291 bits, which should be enough. Need to check the incoming range and domain
1292 to ensure this is an appropriate loss of precision though. */
1295 for (i = j = 0; i < n; i++, j += 4) {
1296 GstClockTime newx4, newy4;
1298 newx4 = newx[j] >> 4;
1299 newy4 = newy[j] >> 4;
1301 sxx += newx4 * newx4 - xbar4 * xbar4;
1302 syy += newy4 * newy4 - ybar4 * ybar4;
1303 sxy += newx4 * newy4 - xbar4 * ybar4;
1306 if (G_UNLIKELY (sxx == 0))
1312 *b = (ybar + ymin) - gst_util_uint64_scale (xbar, *m_num, *m_denom);
1313 *r_squared = ((double) sxy * (double) sxy) / ((double) sxx * (double) syy);
1315 #ifdef DEBUGGING_ENABLED
1316 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, " m = %g",
1317 ((double) *m_num) / *m_denom);
1318 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, " b = %" G_GUINT64_FORMAT,
1320 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, " xbase = %" G_GUINT64_FORMAT,
1322 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, " r2 = %g", *r_squared);
1329 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "sxx == 0, regression failed");
1335 * gst_clock_add_observation:
1336 * @clock: a #GstClock
1337 * @slave: a time on the slave
1338 * @master: a time on the master
1339 * @r_squared: (out): a pointer to hold the result
1341 * The time @master of the master clock and the time @slave of the slave
1342 * clock are added to the list of observations. If enough observations
1343 * are available, a linear regression algorithm is run on the
1344 * observations and @clock is recalibrated.
1346 * If this functions returns %TRUE, @r_squared will contain the
1347 * correlation coefficient of the interpolation. A value of 1.0
1348 * means a perfect regression was performed. This value can
1349 * be used to control the sampling frequency of the master and slave
1352 * Returns: %TRUE if enough observations were added to run the
1353 * regression algorithm.
1358 gst_clock_add_observation (GstClock * clock, GstClockTime slave,
1359 GstClockTime master, gdouble * r_squared)
1361 GstClockTime m_num, m_denom, b, xbase;
1362 GstClockPrivate *priv;
1364 g_return_val_if_fail (GST_IS_CLOCK (clock), FALSE);
1365 g_return_val_if_fail (r_squared != NULL, FALSE);
1369 GST_CLOCK_SLAVE_LOCK (clock);
1371 GST_CAT_LOG_OBJECT (GST_CAT_CLOCK, clock,
1372 "adding observation slave %" GST_TIME_FORMAT ", master %" GST_TIME_FORMAT,
1373 GST_TIME_ARGS (slave), GST_TIME_ARGS (master));
1375 priv->times[(4 * priv->time_index)] = slave;
1376 priv->times[(4 * priv->time_index) + 2] = master;
1379 if (G_UNLIKELY (priv->time_index == priv->window_size)) {
1380 priv->filling = FALSE;
1381 priv->time_index = 0;
1384 if (G_UNLIKELY (priv->filling && priv->time_index < priv->window_threshold))
1387 if (!do_linear_regression (clock, &m_num, &m_denom, &b, &xbase, r_squared))
1390 GST_CLOCK_SLAVE_UNLOCK (clock);
1392 GST_CAT_LOG_OBJECT (GST_CAT_CLOCK, clock,
1393 "adjusting clock to m=%" G_GUINT64_FORMAT "/%" G_GUINT64_FORMAT ", b=%"
1394 G_GUINT64_FORMAT " (rsquared=%g)", m_num, m_denom, b, *r_squared);
1396 /* if we have a valid regression, adjust the clock */
1397 gst_clock_set_calibration (clock, xbase, b, m_num, m_denom);
1403 GST_CLOCK_SLAVE_UNLOCK (clock);
1408 /* no valid regression has been done, ignore the result then */
1409 GST_CLOCK_SLAVE_UNLOCK (clock);
1415 * gst_clock_set_timeout:
1416 * @clock: a #GstClock
1417 * @timeout: a timeout
1419 * Set the amount of time, in nanoseconds, to sample master and slave
1423 gst_clock_set_timeout (GstClock * clock, GstClockTime timeout)
1425 g_return_if_fail (GST_IS_CLOCK (clock));
1427 GST_CLOCK_SLAVE_LOCK (clock);
1428 clock->priv->timeout = timeout;
1429 GST_CLOCK_SLAVE_UNLOCK (clock);
1433 * gst_clock_get_timeout:
1434 * @clock: a #GstClock
1436 * Get the amount of time that master and slave clocks are sampled.
1438 * Returns: the interval between samples.
1441 gst_clock_get_timeout (GstClock * clock)
1443 GstClockTime result;
1445 g_return_val_if_fail (GST_IS_CLOCK (clock), GST_CLOCK_TIME_NONE);
1447 GST_CLOCK_SLAVE_LOCK (clock);
1448 result = clock->priv->timeout;
1449 GST_CLOCK_SLAVE_UNLOCK (clock);
1455 gst_clock_set_property (GObject * object, guint prop_id,
1456 const GValue * value, GParamSpec * pspec)
1459 GstClockPrivate *priv;
1461 clock = GST_CLOCK (object);
1465 case PROP_WINDOW_SIZE:
1466 GST_CLOCK_SLAVE_LOCK (clock);
1467 priv->window_size = g_value_get_int (value);
1468 priv->window_threshold = MIN (priv->window_threshold, priv->window_size);
1469 priv->times = g_renew (GstClockTime, priv->times, 4 * priv->window_size);
1470 /* restart calibration */
1471 priv->filling = TRUE;
1472 priv->time_index = 0;
1473 GST_CLOCK_SLAVE_UNLOCK (clock);
1475 case PROP_WINDOW_THRESHOLD:
1476 GST_CLOCK_SLAVE_LOCK (clock);
1477 priv->window_threshold = MIN (g_value_get_int (value), priv->window_size);
1478 GST_CLOCK_SLAVE_UNLOCK (clock);
1481 gst_clock_set_timeout (clock, g_value_get_uint64 (value));
1484 G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
1490 gst_clock_get_property (GObject * object, guint prop_id,
1491 GValue * value, GParamSpec * pspec)
1494 GstClockPrivate *priv;
1496 clock = GST_CLOCK (object);
1500 case PROP_WINDOW_SIZE:
1501 GST_CLOCK_SLAVE_LOCK (clock);
1502 g_value_set_int (value, priv->window_size);
1503 GST_CLOCK_SLAVE_UNLOCK (clock);
1505 case PROP_WINDOW_THRESHOLD:
1506 GST_CLOCK_SLAVE_LOCK (clock);
1507 g_value_set_int (value, priv->window_threshold);
1508 GST_CLOCK_SLAVE_UNLOCK (clock);
1511 g_value_set_uint64 (value, gst_clock_get_timeout (clock));
1514 G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);