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 2009-05-21 (0.10.24)
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_full:
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_full (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_wait_async:
614 * @id: a #GstClockID to wait on
615 * @func: The callback function
616 * @user_data: User data passed in the callback
618 * Register a callback on the given #GstClockID @id with the given
619 * function and user_data. When passing a #GstClockID with an invalid
620 * time to this function, the callback will be called immediately
621 * with a time set to GST_CLOCK_TIME_NONE. The callback will
622 * be called when the time of @id has been reached.
624 * The callback @func can be invoked from any thread, either provided by the
625 * core or from a streaming thread. The application should be prepared for this.
627 * Returns: the result of the non blocking wait.
632 gst_clock_id_wait_async (GstClockID id,
633 GstClockCallback func, gpointer user_data)
635 return gst_clock_id_wait_async_full (id, func, user_data, NULL);
639 * gst_clock_id_unschedule:
640 * @id: The id to unschedule
642 * Cancel an outstanding request with @id. This can either
643 * be an outstanding async notification or a pending sync notification.
644 * After this call, @id cannot be used anymore to receive sync or
645 * async notifications, you need to create a new #GstClockID.
650 gst_clock_id_unschedule (GstClockID id)
652 GstClockEntry *entry;
654 GstClockClass *cclass;
656 g_return_if_fail (id != NULL);
658 entry = (GstClockEntry *) id;
659 clock = entry->clock;
661 cclass = GST_CLOCK_GET_CLASS (clock);
663 if (G_LIKELY (cclass->unschedule))
664 cclass->unschedule (clock, entry);
669 * GstClock abstract base class implementation
671 #define gst_clock_parent_class parent_class
672 G_DEFINE_TYPE (GstClock, gst_clock, GST_TYPE_OBJECT);
675 gst_clock_class_init (GstClockClass * klass)
677 GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
679 #ifndef GST_DISABLE_TRACE
680 _gst_clock_entry_trace = _gst_alloc_trace_register ("GstClockEntry", -1);
683 gobject_class->dispose = gst_clock_dispose;
684 gobject_class->finalize = gst_clock_finalize;
685 gobject_class->set_property = gst_clock_set_property;
686 gobject_class->get_property = gst_clock_get_property;
688 g_object_class_install_property (gobject_class, PROP_WINDOW_SIZE,
689 g_param_spec_int ("window-size", "Window size",
690 "The size of the window used to calculate rate and offset", 2, 1024,
691 DEFAULT_WINDOW_SIZE, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
692 g_object_class_install_property (gobject_class, PROP_WINDOW_THRESHOLD,
693 g_param_spec_int ("window-threshold", "Window threshold",
694 "The threshold to start calculating rate and offset", 2, 1024,
695 DEFAULT_WINDOW_THRESHOLD,
696 G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
697 g_object_class_install_property (gobject_class, PROP_TIMEOUT,
698 g_param_spec_uint64 ("timeout", "Timeout",
699 "The amount of time, in nanoseconds, to sample master and slave clocks",
700 0, G_MAXUINT64, DEFAULT_TIMEOUT,
701 G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
703 g_type_class_add_private (klass, sizeof (GstClockPrivate));
707 gst_clock_init (GstClock * clock)
709 GstClockPrivate *priv;
712 G_TYPE_INSTANCE_GET_PRIVATE (clock, GST_TYPE_CLOCK, GstClockPrivate);
716 priv->internal_calibration = 0;
717 priv->external_calibration = 0;
718 priv->rate_numerator = 1;
719 priv->rate_denominator = 1;
721 g_mutex_init (&priv->slave_lock);
722 priv->window_size = DEFAULT_WINDOW_SIZE;
723 priv->window_threshold = DEFAULT_WINDOW_THRESHOLD;
724 priv->filling = TRUE;
725 priv->time_index = 0;
726 priv->timeout = DEFAULT_TIMEOUT;
727 priv->times = g_new0 (GstClockTime, 4 * priv->window_size);
731 gst_clock_dispose (GObject * object)
733 GstClock *clock = GST_CLOCK (object);
736 GST_OBJECT_LOCK (clock);
737 master_p = &clock->priv->master;
738 gst_object_replace ((GstObject **) master_p, NULL);
739 GST_OBJECT_UNLOCK (clock);
741 G_OBJECT_CLASS (parent_class)->dispose (object);
745 gst_clock_finalize (GObject * object)
747 GstClock *clock = GST_CLOCK (object);
749 GST_CLOCK_SLAVE_LOCK (clock);
750 if (clock->priv->clockid) {
751 gst_clock_id_unschedule (clock->priv->clockid);
752 gst_clock_id_unref (clock->priv->clockid);
753 clock->priv->clockid = NULL;
755 g_free (clock->priv->times);
756 clock->priv->times = NULL;
757 GST_CLOCK_SLAVE_UNLOCK (clock);
759 g_mutex_clear (&clock->priv->slave_lock);
761 G_OBJECT_CLASS (parent_class)->finalize (object);
765 * gst_clock_set_resolution
766 * @clock: a #GstClock
767 * @resolution: The resolution to set
769 * Set the accuracy of the clock. Some clocks have the possibility to operate
770 * with different accuracy at the expense of more resource usage. There is
771 * normally no need to change the default resolution of a clock. The resolution
772 * of a clock can only be changed if the clock has the
773 * #GST_CLOCK_FLAG_CAN_SET_RESOLUTION flag set.
775 * Returns: the new resolution of the clock.
778 gst_clock_set_resolution (GstClock * clock, GstClockTime resolution)
780 GstClockPrivate *priv;
781 GstClockClass *cclass;
783 g_return_val_if_fail (GST_IS_CLOCK (clock), 0);
784 g_return_val_if_fail (resolution != 0, 0);
786 cclass = GST_CLOCK_GET_CLASS (clock);
789 if (cclass->change_resolution)
791 cclass->change_resolution (clock, priv->resolution, resolution);
793 return priv->resolution;
797 * gst_clock_get_resolution
798 * @clock: a #GstClock
800 * Get the accuracy of the clock. The accuracy of the clock is the granularity
801 * of the values returned by gst_clock_get_time().
803 * Returns: the resolution of the clock in units of #GstClockTime.
808 gst_clock_get_resolution (GstClock * clock)
810 GstClockClass *cclass;
812 g_return_val_if_fail (GST_IS_CLOCK (clock), 0);
814 cclass = GST_CLOCK_GET_CLASS (clock);
816 if (cclass->get_resolution)
817 return cclass->get_resolution (clock);
823 * gst_clock_adjust_unlocked
824 * @clock: a #GstClock to use
825 * @internal: a clock time
827 * Converts the given @internal clock time to the external time, adjusting for the
828 * rate and reference time set with gst_clock_set_calibration() and making sure
829 * that the returned time is increasing. This function should be called with the
830 * clock's OBJECT_LOCK held and is mainly used by clock subclasses.
832 * This function is the reverse of gst_clock_unadjust_unlocked().
834 * Returns: the converted time of the clock.
837 gst_clock_adjust_unlocked (GstClock * clock, GstClockTime internal)
839 GstClockTime ret, cinternal, cexternal, cnum, cdenom;
840 GstClockPrivate *priv = clock->priv;
842 /* get calibration values for readability */
843 cinternal = priv->internal_calibration;
844 cexternal = priv->external_calibration;
845 cnum = priv->rate_numerator;
846 cdenom = priv->rate_denominator;
848 /* avoid divide by 0 */
849 if (G_UNLIKELY (cdenom == 0))
852 /* The formula is (internal - cinternal) * cnum / cdenom + cexternal
854 * Since we do math on unsigned 64-bit ints we have to special case for
855 * internal < cinternal to get the sign right. this case is not very common,
858 if (G_LIKELY (internal >= cinternal)) {
859 ret = internal - cinternal;
860 ret = gst_util_uint64_scale (ret, cnum, cdenom);
863 ret = cinternal - internal;
864 ret = gst_util_uint64_scale (ret, cnum, cdenom);
866 if (G_LIKELY (cexternal > ret))
867 ret = cexternal - ret;
872 /* make sure the time is increasing */
873 priv->last_time = MAX (ret, priv->last_time);
875 return priv->last_time;
879 * gst_clock_unadjust_unlocked
880 * @clock: a #GstClock to use
881 * @external: an external clock time
883 * Converts the given @external clock time to the internal time of @clock,
884 * using the rate and reference time set with gst_clock_set_calibration().
885 * This function should be called with the clock's OBJECT_LOCK held and
886 * is mainly used by clock subclasses.
888 * This function is the reverse of gst_clock_adjust_unlocked().
890 * Returns: the internal time of the clock corresponding to @external.
895 gst_clock_unadjust_unlocked (GstClock * clock, GstClockTime external)
897 GstClockTime ret, cinternal, cexternal, cnum, cdenom;
898 GstClockPrivate *priv = clock->priv;
900 /* get calibration values for readability */
901 cinternal = priv->internal_calibration;
902 cexternal = priv->external_calibration;
903 cnum = priv->rate_numerator;
904 cdenom = priv->rate_denominator;
906 /* avoid divide by 0 */
907 if (G_UNLIKELY (cnum == 0))
910 /* The formula is (external - cexternal) * cdenom / cnum + cinternal */
911 if (G_LIKELY (external >= cexternal)) {
912 ret = external - cexternal;
913 ret = gst_util_uint64_scale (ret, cdenom, cnum);
916 ret = cexternal - external;
917 ret = gst_util_uint64_scale (ret, cdenom, cnum);
918 if (G_LIKELY (cinternal > ret))
919 ret = cinternal - ret;
927 * gst_clock_get_internal_time
928 * @clock: a #GstClock to query
930 * Gets the current internal time of the given clock. The time is returned
931 * unadjusted for the offset and the rate.
933 * Returns: the internal time of the clock. Or GST_CLOCK_TIME_NONE when
934 * given invalid input.
939 gst_clock_get_internal_time (GstClock * clock)
942 GstClockClass *cclass;
944 g_return_val_if_fail (GST_IS_CLOCK (clock), GST_CLOCK_TIME_NONE);
946 cclass = GST_CLOCK_GET_CLASS (clock);
948 if (G_UNLIKELY (cclass->get_internal_time == NULL))
951 ret = cclass->get_internal_time (clock);
953 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "internal time %" GST_TIME_FORMAT,
954 GST_TIME_ARGS (ret));
961 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
962 "internal time not supported, return 0");
963 return G_GINT64_CONSTANT (0);
969 * @clock: a #GstClock to query
971 * Gets the current time of the given clock. The time is always
972 * monotonically increasing and adjusted according to the current
975 * Returns: the time of the clock. Or GST_CLOCK_TIME_NONE when
976 * given invalid input.
981 gst_clock_get_time (GstClock * clock)
986 g_return_val_if_fail (GST_IS_CLOCK (clock), GST_CLOCK_TIME_NONE);
989 /* reget the internal time when we retry to get the most current
991 ret = gst_clock_get_internal_time (clock);
993 seq = read_seqbegin (clock);
994 /* this will scale for rate and offset */
995 ret = gst_clock_adjust_unlocked (clock, ret);
996 } while (read_seqretry (clock, seq));
998 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "adjusted time %" GST_TIME_FORMAT,
999 GST_TIME_ARGS (ret));
1005 * gst_clock_set_calibration
1006 * @clock: a #GstClock to calibrate
1007 * @internal: a reference internal time
1008 * @external: a reference external time
1009 * @rate_num: the numerator of the rate of the clock relative to its
1011 * @rate_denom: the denominator of the rate of the clock
1013 * Adjusts the rate and time of @clock. A rate of 1/1 is the normal speed of
1014 * the clock. Values bigger than 1/1 make the clock go faster.
1016 * @internal and @external are calibration parameters that arrange that
1017 * gst_clock_get_time() should have been @external at internal time @internal.
1018 * This internal time should not be in the future; that is, it should be less
1019 * than the value of gst_clock_get_internal_time() when this function is called.
1021 * Subsequent calls to gst_clock_get_time() will return clock times computed as
1025 * time = (internal_time - internal) * rate_num / rate_denom + external
1028 * This formula is implemented in gst_clock_adjust_unlocked(). Of course, it
1029 * tries to do the integer arithmetic as precisely as possible.
1031 * Note that gst_clock_get_time() always returns increasing values so when you
1032 * move the clock backwards, gst_clock_get_time() will report the previous value
1033 * until the clock catches up.
1038 gst_clock_set_calibration (GstClock * clock, GstClockTime internal, GstClockTime
1039 external, GstClockTime rate_num, GstClockTime rate_denom)
1041 GstClockPrivate *priv;
1043 g_return_if_fail (GST_IS_CLOCK (clock));
1044 g_return_if_fail (rate_num != GST_CLOCK_TIME_NONE);
1045 g_return_if_fail (rate_denom > 0 && rate_denom != GST_CLOCK_TIME_NONE);
1049 write_seqlock (clock);
1050 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
1051 "internal %" GST_TIME_FORMAT " external %" GST_TIME_FORMAT " %"
1052 G_GUINT64_FORMAT "/%" G_GUINT64_FORMAT " = %f", GST_TIME_ARGS (internal),
1053 GST_TIME_ARGS (external), rate_num, rate_denom,
1054 gst_guint64_to_gdouble (rate_num) / gst_guint64_to_gdouble (rate_denom));
1056 priv->internal_calibration = internal;
1057 priv->external_calibration = external;
1058 priv->rate_numerator = rate_num;
1059 priv->rate_denominator = rate_denom;
1060 write_sequnlock (clock);
1064 * gst_clock_get_calibration
1065 * @clock: a #GstClock
1066 * @internal: (out) (allow-none): a location to store the internal time
1067 * @external: (out) (allow-none): a location to store the external time
1068 * @rate_num: (out) (allow-none): a location to store the rate numerator
1069 * @rate_denom: (out) (allow-none): a location to store the rate denominator
1071 * Gets the internal rate and reference time of @clock. See
1072 * gst_clock_set_calibration() for more information.
1074 * @internal, @external, @rate_num, and @rate_denom can be left %NULL if the
1075 * caller is not interested in the values.
1080 gst_clock_get_calibration (GstClock * clock, GstClockTime * internal,
1081 GstClockTime * external, GstClockTime * rate_num, GstClockTime * rate_denom)
1084 GstClockPrivate *priv;
1086 g_return_if_fail (GST_IS_CLOCK (clock));
1091 seq = read_seqbegin (clock);
1093 *rate_num = priv->rate_numerator;
1095 *rate_denom = priv->rate_denominator;
1097 *external = priv->external_calibration;
1099 *internal = priv->internal_calibration;
1100 } while (read_seqretry (clock, seq));
1103 /* will be called repeatedly to sample the master and slave clock
1104 * to recalibrate the clock */
1106 gst_clock_slave_callback (GstClock * master, GstClockTime time,
1107 GstClockID id, GstClock * clock)
1109 GstClockTime stime, mtime;
1112 stime = gst_clock_get_internal_time (clock);
1113 mtime = gst_clock_get_time (master);
1115 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
1116 "master %" GST_TIME_FORMAT ", slave %" GST_TIME_FORMAT,
1117 GST_TIME_ARGS (mtime), GST_TIME_ARGS (stime));
1119 gst_clock_add_observation (clock, stime, mtime, &r_squared);
1121 /* FIXME, we can use the r_squared value to adjust the timeout
1122 * value of the clockid */
1128 * gst_clock_set_master
1129 * @clock: a #GstClock
1130 * @master: (allow-none): a master #GstClock
1132 * Set @master as the master clock for @clock. @clock will be automatically
1133 * calibrated so that gst_clock_get_time() reports the same time as the
1136 * A clock provider that slaves its clock to a master can get the current
1137 * calibration values with gst_clock_get_calibration().
1139 * @master can be %NULL in which case @clock will not be slaved anymore. It will
1140 * however keep reporting its time adjusted with the last configured rate
1143 * Returns: %TRUE if the clock is capable of being slaved to a master clock.
1144 * Trying to set a master on a clock without the
1145 * #GST_CLOCK_FLAG_CAN_SET_MASTER flag will make this function return %FALSE.
1150 gst_clock_set_master (GstClock * clock, GstClock * master)
1152 GstClock **master_p;
1153 GstClockPrivate *priv;
1155 g_return_val_if_fail (GST_IS_CLOCK (clock), FALSE);
1156 g_return_val_if_fail (master != clock, FALSE);
1158 GST_OBJECT_LOCK (clock);
1159 /* we always allow setting the master to NULL */
1160 if (master && !GST_OBJECT_FLAG_IS_SET (clock, GST_CLOCK_FLAG_CAN_SET_MASTER))
1162 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
1163 "slaving %p to master clock %p", clock, master);
1164 GST_OBJECT_UNLOCK (clock);
1168 GST_CLOCK_SLAVE_LOCK (clock);
1169 if (priv->clockid) {
1170 gst_clock_id_unschedule (priv->clockid);
1171 gst_clock_id_unref (priv->clockid);
1172 priv->clockid = NULL;
1175 priv->filling = TRUE;
1176 priv->time_index = 0;
1177 /* use the master periodic id to schedule sampling and
1178 * clock calibration. */
1179 priv->clockid = gst_clock_new_periodic_id (master,
1180 gst_clock_get_time (master), priv->timeout);
1181 gst_clock_id_wait_async_full (priv->clockid,
1182 (GstClockCallback) gst_clock_slave_callback,
1183 gst_object_ref (clock), (GDestroyNotify) gst_object_unref);
1185 GST_CLOCK_SLAVE_UNLOCK (clock);
1187 GST_OBJECT_LOCK (clock);
1188 master_p = &priv->master;
1189 gst_object_replace ((GstObject **) master_p, (GstObject *) master);
1190 GST_OBJECT_UNLOCK (clock);
1197 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
1198 "cannot be slaved to a master clock");
1199 GST_OBJECT_UNLOCK (clock);
1205 * gst_clock_get_master:
1206 * @clock: a #GstClock
1208 * Get the master clock that @clock is slaved to or %NULL when the clock is
1209 * not slaved to any master clock.
1211 * Returns: (transfer full): a master #GstClock or %NULL when this clock is
1212 * not slaved to a master clock. Unref after usage.
1217 gst_clock_get_master (GstClock * clock)
1219 GstClock *result = NULL;
1220 GstClockPrivate *priv;
1222 g_return_val_if_fail (GST_IS_CLOCK (clock), NULL);
1226 GST_OBJECT_LOCK (clock);
1228 result = gst_object_ref (priv->master);
1229 GST_OBJECT_UNLOCK (clock);
1234 /* http://mathworld.wolfram.com/LeastSquaresFitting.html
1238 do_linear_regression (GstClock * clock, GstClockTime * m_num,
1239 GstClockTime * m_denom, GstClockTime * b, GstClockTime * xbase,
1240 gdouble * r_squared)
1242 GstClockTime *newx, *newy;
1243 GstClockTime xmin, ymin, xbar, ybar, xbar4, ybar4;
1244 GstClockTimeDiff sxx, sxy, syy;
1245 GstClockTime *x, *y;
1248 GstClockPrivate *priv;
1250 xbar = ybar = sxx = syy = sxy = 0;
1255 y = priv->times + 2;
1256 n = priv->filling ? priv->time_index : priv->window_size;
1258 #ifdef DEBUGGING_ENABLED
1259 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "doing regression on:");
1260 for (i = j = 0; i < n; i++, j += 4)
1261 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
1262 " %" G_GUINT64_FORMAT " %" G_GUINT64_FORMAT, x[j], y[j]);
1265 xmin = ymin = G_MAXUINT64;
1266 for (i = j = 0; i < n; i++, j += 4) {
1267 xmin = MIN (xmin, x[j]);
1268 ymin = MIN (ymin, y[j]);
1271 #ifdef DEBUGGING_ENABLED
1272 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "min x: %" G_GUINT64_FORMAT,
1274 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "min y: %" G_GUINT64_FORMAT,
1278 newx = priv->times + 1;
1279 newy = priv->times + 3;
1281 /* strip off unnecessary bits of precision */
1282 for (i = j = 0; i < n; i++, j += 4) {
1283 newx[j] = x[j] - xmin;
1284 newy[j] = y[j] - ymin;
1287 #ifdef DEBUGGING_ENABLED
1288 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "reduced numbers:");
1289 for (i = j = 0; i < n; i++, j += 4)
1290 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock,
1291 " %" G_GUINT64_FORMAT " %" G_GUINT64_FORMAT, newx[j], newy[j]);
1294 /* have to do this precisely otherwise the results are pretty much useless.
1295 * should guarantee that none of these accumulators can overflow */
1297 /* quantities on the order of 1e10 -> 30 bits; window size a max of 2^10, so
1298 this addition could end up around 2^40 or so -- ample headroom */
1299 for (i = j = 0; i < n; i++, j += 4) {
1306 #ifdef DEBUGGING_ENABLED
1307 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, " xbar = %" G_GUINT64_FORMAT,
1309 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, " ybar = %" G_GUINT64_FORMAT,
1313 /* multiplying directly would give quantities on the order of 1e20 -> 60 bits;
1314 times the window size that's 70 which is too much. Instead we (1) subtract
1315 off the xbar*ybar in the loop instead of after, to avoid accumulation; (2)
1316 shift off 4 bits from each multiplicand, giving an expected ceiling of 52
1317 bits, which should be enough. Need to check the incoming range and domain
1318 to ensure this is an appropriate loss of precision though. */
1321 for (i = j = 0; i < n; i++, j += 4) {
1322 GstClockTime newx4, newy4;
1324 newx4 = newx[j] >> 4;
1325 newy4 = newy[j] >> 4;
1327 sxx += newx4 * newx4 - xbar4 * xbar4;
1328 syy += newy4 * newy4 - ybar4 * ybar4;
1329 sxy += newx4 * newy4 - xbar4 * ybar4;
1332 if (G_UNLIKELY (sxx == 0))
1338 *b = (ybar + ymin) - gst_util_uint64_scale (xbar, *m_num, *m_denom);
1339 *r_squared = ((double) sxy * (double) sxy) / ((double) sxx * (double) syy);
1341 #ifdef DEBUGGING_ENABLED
1342 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, " m = %g",
1343 ((double) *m_num) / *m_denom);
1344 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, " b = %" G_GUINT64_FORMAT,
1346 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, " xbase = %" G_GUINT64_FORMAT,
1348 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, " r2 = %g", *r_squared);
1355 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, clock, "sxx == 0, regression failed");
1361 * gst_clock_add_observation
1362 * @clock: a #GstClock
1363 * @slave: a time on the slave
1364 * @master: a time on the master
1365 * @r_squared: (out): a pointer to hold the result
1367 * The time @master of the master clock and the time @slave of the slave
1368 * clock are added to the list of observations. If enough observations
1369 * are available, a linear regression algorithm is run on the
1370 * observations and @clock is recalibrated.
1372 * If this functions returns %TRUE, @r_squared will contain the
1373 * correlation coefficient of the interpolation. A value of 1.0
1374 * means a perfect regression was performed. This value can
1375 * be used to control the sampling frequency of the master and slave
1378 * Returns: %TRUE if enough observations were added to run the
1379 * regression algorithm.
1384 gst_clock_add_observation (GstClock * clock, GstClockTime slave,
1385 GstClockTime master, gdouble * r_squared)
1387 GstClockTime m_num, m_denom, b, xbase;
1388 GstClockPrivate *priv;
1390 g_return_val_if_fail (GST_IS_CLOCK (clock), FALSE);
1391 g_return_val_if_fail (r_squared != NULL, FALSE);
1395 GST_CLOCK_SLAVE_LOCK (clock);
1397 GST_CAT_LOG_OBJECT (GST_CAT_CLOCK, clock,
1398 "adding observation slave %" GST_TIME_FORMAT ", master %" GST_TIME_FORMAT,
1399 GST_TIME_ARGS (slave), GST_TIME_ARGS (master));
1401 priv->times[(4 * priv->time_index)] = slave;
1402 priv->times[(4 * priv->time_index) + 2] = master;
1405 if (G_UNLIKELY (priv->time_index == priv->window_size)) {
1406 priv->filling = FALSE;
1407 priv->time_index = 0;
1410 if (G_UNLIKELY (priv->filling && priv->time_index < priv->window_threshold))
1413 if (!do_linear_regression (clock, &m_num, &m_denom, &b, &xbase, r_squared))
1416 GST_CLOCK_SLAVE_UNLOCK (clock);
1418 GST_CAT_LOG_OBJECT (GST_CAT_CLOCK, clock,
1419 "adjusting clock to m=%" G_GUINT64_FORMAT "/%" G_GUINT64_FORMAT ", b=%"
1420 G_GUINT64_FORMAT " (rsquared=%g)", m_num, m_denom, b, *r_squared);
1422 /* if we have a valid regression, adjust the clock */
1423 gst_clock_set_calibration (clock, xbase, b, m_num, m_denom);
1429 GST_CLOCK_SLAVE_UNLOCK (clock);
1434 /* no valid regression has been done, ignore the result then */
1435 GST_CLOCK_SLAVE_UNLOCK (clock);
1441 gst_clock_set_timeout (GstClock * clock, GstClockTime timeout)
1443 clock->priv->timeout = timeout;
1447 gst_clock_get_timeout (GstClock * clock)
1449 return clock->priv->timeout;
1453 gst_clock_set_property (GObject * object, guint prop_id,
1454 const GValue * value, GParamSpec * pspec)
1457 GstClockPrivate *priv;
1459 clock = GST_CLOCK (object);
1463 case PROP_WINDOW_SIZE:
1464 GST_CLOCK_SLAVE_LOCK (clock);
1465 priv->window_size = g_value_get_int (value);
1466 priv->window_threshold = MIN (priv->window_threshold, priv->window_size);
1467 priv->times = g_renew (GstClockTime, priv->times, 4 * priv->window_size);
1468 /* restart calibration */
1469 priv->filling = TRUE;
1470 priv->time_index = 0;
1471 GST_CLOCK_SLAVE_UNLOCK (clock);
1473 case PROP_WINDOW_THRESHOLD:
1474 GST_CLOCK_SLAVE_LOCK (clock);
1475 priv->window_threshold = MIN (g_value_get_int (value), priv->window_size);
1476 GST_CLOCK_SLAVE_UNLOCK (clock);
1479 GST_CLOCK_SLAVE_LOCK (clock);
1480 priv->timeout = g_value_get_uint64 (value);
1481 GST_CLOCK_SLAVE_UNLOCK (clock);
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 GST_CLOCK_SLAVE_LOCK (clock);
1512 g_value_set_uint64 (value, priv->timeout);
1513 GST_CLOCK_SLAVE_UNLOCK (clock);
1516 G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);