#[repr(transparent)]pub struct Clock { /* private fields */ }
Expand description
GStreamer uses a global clock to synchronize the plugins in a pipeline.
Different clock implementations are possible by implementing this abstract
base class or, more conveniently, by subclassing SystemClock
.
The Clock
returns a monotonically increasing time with the method
ClockExt::time()
. Its accuracy and base time depend on the specific
clock implementation but time is always expressed in nanoseconds. Since the
baseline of the clock is undefined, the clock time returned is not
meaningful in itself, what matters are the deltas between two clock times.
The time returned by a clock is called the absolute time.
The pipeline uses the clock to calculate the running time. Usually all
renderers synchronize to the global clock using the buffer timestamps, the
EventType::Segment
events and the element’s base time, see Pipeline
.
A clock implementation can support periodic and single shot clock notifications both synchronous and asynchronous.
One first needs to create a GstClockID
for the periodic or single shot
notification using ClockExtManual::new_single_shot_id()
or
ClockExtManual::new_periodic_id()
.
To perform a blocking wait for the specific time of the GstClockID
use
gst_clock_id_wait()
. To receive a callback when the specific time is reached
in the clock use gst_clock_id_wait_async()
. Both these calls can be
interrupted with the gst_clock_id_unschedule()
call. If the blocking wait is
unscheduled a return value of ClockReturn::Unscheduled
is returned.
Periodic callbacks scheduled async will be repeatedly called automatically
until they are unscheduled. To schedule a sync periodic callback,
gst_clock_id_wait()
should be called repeatedly.
The async callbacks can happen from any thread, either provided by the core or from a streaming thread. The application should be prepared for this.
A GstClockID
that has been unscheduled cannot be used again for any wait
operation, a new GstClockID
should be created and the old unscheduled one
should be destroyed with gst_clock_id_unref()
.
It is possible to perform a blocking wait on the same GstClockID
from
multiple threads. However, registering the same GstClockID
for multiple
async notifications is not possible, the callback will only be called for
the thread registering the entry last.
None of the wait operations unref the GstClockID
, the owner is responsible
for unreffing the ids itself. This holds for both periodic and single shot
notifications. The reason being that the owner of the GstClockID
has to
keep a handle to the GstClockID
to unblock the wait on FLUSHING events or
state changes and if the entry would be unreffed automatically, the handle
might become invalid without any notification.
These clock operations do not operate on the running time, so the callbacks will also occur when not in PLAYING state as if the clock just keeps on running. Some clocks however do not progress when the element that provided the clock is not PLAYING.
When a clock has the ClockFlags::CAN_SET_MASTER
flag set, it can be
slaved to another Clock
with ClockExt::set_master()
. The clock will
then automatically be synchronized to this master clock by repeatedly
sampling the master clock and the slave clock and recalibrating the slave
clock with ClockExt::set_calibration()
. This feature is mostly useful for
plugins that have an internal clock but must operate with another clock
selected by the Pipeline
. They can track the offset and rate difference
of their internal clock relative to the master clock by using the
ClockExt::calibration()
function.
The master/slave synchronisation can be tuned with the timeout
,
window-size
and window-threshold
properties.
The timeout
property defines the interval to sample the master
clock and run the calibration functions. window-size
defines the
number of samples to use when calibrating and window-threshold
defines the minimum number of samples before the calibration is performed.
This is an Abstract Base Class, you cannot instantiate it.
Properties
timeout
Readable | Writeable
window-size
Readable | Writeable
window-threshold
Readable | Writeable
Object
name
Readable | Writeable | Construct
parent
The parent of the object. Please note, that when changing the ‘parent’
property, we don’t emit notify
and deep-notify
signals due to locking issues. In some cases one can use
element-added
or element-removed
signals on the parent to
achieve a similar effect.
Readable | Writeable
Signals
synced
Signaled on clocks with ClockFlags::NEEDS_STARTUP_SYNC
set once
the clock is synchronized, or when it completely lost synchronization.
This signal will not be emitted on clocks without the flag.
This signal will be emitted from an arbitrary thread, most likely not the application’s main thread.
Object
deep-notify
The deep notify signal is used to be notified of property changes. It is typically attached to the toplevel bin to receive notifications from all the elements contained in that bin.
Detailed
Implements
Implementations§
source§impl Clock
impl Clock
pub fn adjust_with_calibration(
internal_target: ClockTime,
cinternal: ClockTime,
cexternal: ClockTime,
cnum: ClockTime,
cdenom: ClockTime
) -> ClockTime
pub fn unadjust_with_calibration(
external_target: ClockTime,
cinternal: ClockTime,
cexternal: ClockTime,
cnum: ClockTime,
cdenom: ClockTime
) -> ClockTime
Trait Implementations§
source§impl HasParamSpec for Clock
impl HasParamSpec for Clock
source§impl<T: ClockImpl> IsSubclassable<T> for Clock
impl<T: ClockImpl> IsSubclassable<T> for Clock
source§fn class_init(klass: &mut Class<Self>)
fn class_init(klass: &mut Class<Self>)
source§fn instance_init(instance: &mut InitializingObject<T>)
fn instance_init(instance: &mut InitializingObject<T>)
source§impl Ord for Clock
impl Ord for Clock
source§impl<OT: ObjectType> PartialEq<OT> for Clock
impl<OT: ObjectType> PartialEq<OT> for Clock
source§impl<OT: ObjectType> PartialOrd<OT> for Clock
impl<OT: ObjectType> PartialOrd<OT> for Clock
1.0.0 · source§fn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
self
and other
) and is used by the <=
operator. Read moresource§impl StaticType for Clock
impl StaticType for Clock
source§fn static_type() -> Type
fn static_type() -> Type
Self
.impl Eq for Clock
impl IsA<Clock> for SystemClock
impl IsA<Object> for Clock
impl Send for Clock
impl Sync for Clock
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