Struct gstreamer::Clock

pub struct Clock(_);

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 crate::SystemClock.

The crate::Clock returns a monotonically increasing time with the method [crate::prelude::ClockExt::get_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 newsegment events and the element’s base time, see crate::Pipeline.

A clock implementation can support periodic and single shot clock notifications both synchronous and asynchronous.

One first needs to create a [crate::ClockID] for the periodic or single shot notification using [crate::prelude::ClockExt::new_single_shot_id()] or [crate::prelude::ClockExt::new_periodic_id()].

To perform a blocking wait for the specific time of the [crate::ClockID] use the [Self::id_wait()]. To receive a callback when the specific time is reached in the clock use [Self::id_wait_async()]. Both these calls can be interrupted with the [Self::id_unschedule()] call. If the blocking wait is unscheduled a return value of crate::ClockReturn::Unscheduled is returned.

Periodic callbacks scheduled async will be repeatedly called automatically until it is unscheduled. To schedule a sync periodic callback, [Self::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 [crate::ClockID] that has been unscheduled cannot be used again for any wait operation, a new [crate::ClockID] should be created and the old unscheduled one should be destroyed with [Self::id_unref()].

It is possible to perform a blocking wait on the same [crate::ClockID] from multiple threads. However, registering the same [crate::ClockID] 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 [crate::ClockID], 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 [crate::ClockID] has to keep a handle to the [crate::ClockID] 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 [crate::ClockFlags::CanSetMaster] flag set, it can be slaved to another crate::Clock with the crate::prelude::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 crate::prelude::ClockExt::set_calibration(). This feature is mostly useful for plugins that have an internal clock but must operate with another clock selected by the crate::Pipeline. They can track the offset and rate difference of their internal clock relative to the master clock by using the [crate::prelude::ClockExt::get_calibration()] function.

The master/slave synchronisation can be tuned with the [crate::Clock:timeout], [crate::Clock:window-size] and [crate::Clock:window-threshold] properties. The [crate::Clock:timeout] property defines the interval to sample the master clock and run the calibration functions. [crate::Clock:window-size] defines the number of samples to use when calibrating and [crate::Clock:window-threshold] defines the minimum number of samples before the calibration is performed.

This is an Abstract Base Class, you cannot instantiate it.

Implements

crate::prelude::ClockExt, crate::prelude::GstObjectExt, glib::object::ObjectExt, crate::prelude::ClockExtManual

Implementations

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

impl Clone for Clock

fn clone(&self) -> Clock

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Clock

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Hash for Clock

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given Hasher.

impl<T: ClockImpl> IsSubclassable<T> for Clock

fn class_init(klass: &mut Class<Self>)

Override the virtual methods of this class for the given subclass and do other class initialization.

fn instance_init(instance: &mut InitializingObject<T>)

Instance specific initialization.

impl Ord for Clock

fn cmp(&self, other: &Clock) -> Ordering

This method returns an Ordering between self and other.

#[must_use]

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

#[must_use]

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

#[must_use]

fn clamp(self, min: Self, max: Self) -> Self

Restrict a value to a certain interval.

impl ParentClassIs for Clock

type Parent = Object

impl<T: ObjectType> PartialEq<T> for Clock

fn eq(&self, other: &T) -> bool

This method tests for self and other values to be equal, and is used by ==.

#[must_use]

fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<T: ObjectType> PartialOrd<T> for Clock

fn partial_cmp(&self, other: &T) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

#[must_use]

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

#[must_use]

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

#[must_use]

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

#[must_use]

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl StaticType for Clock

fn static_type() -> Type

Returns the type identifier of Self.

impl Eq for Clock

impl IsA<Clock> for SystemClock

impl IsA<Object> for Clock

impl Send for Clock

impl StructuralEq for Clock

impl Sync for Clock