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 SystemClock.

The Clock returns a monotonically increasing time with the method 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 Pipeline.

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

One first needs to create a ClockID for the periodic or single shot notification using ClockExt::new_single_shot_id or ClockExt::new_periodic_id.

To perform a blocking wait for the specific time of the ClockID use the Clock::id_wait. To receive a callback when the specific time is reached in the clock use Clock::id_wait_async. Both these calls can be interrupted with the 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 it is unscheduled. To schedule a sync periodic callback, 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 ClockID that has been unscheduled cannot be used again for any wait operation, a new ClockID should be created and the old unscheduled one should be destroyed with Clock::id_unref.

It is possible to perform a blocking wait on the same ClockID from multiple threads. However, registering the same 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 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 ClockID has to keep a handle to the 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 ClockFlags::CanSetMaster flag set, it can be slaved to another Clock with the 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::get_calibration function.

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


ClockExt, GstObjectExt, glib::object::ObjectExt


impl Clock

Trait Implementations

impl Clone for Clock

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

impl Hash for Clock

Feeds this value into the given [Hasher]. Read more

Feeds a slice of this type into the given [Hasher]. Read more

impl Ord for Clock

This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

impl StaticType for Clock

Returns the type identifier of Self.

impl<T: IsA<Object>> PartialEq<T> for Clock

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

This method tests for !=.

impl Eq for Clock

impl<T: IsA<Object>> PartialOrd<T> for Clock

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

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

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

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

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

impl Debug for Clock

Formats the value using the given formatter. Read more

impl IsA<Object> for Clock

impl IsA<Object> for Clock

impl Send for Clock

impl Sync for Clock

impl IsA<Clock> for SystemClock