Struct gstreamer::Clock

#[repr(transparent)]
pub struct Clock { /* private fields */ }

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

ClockExt, GstObjectExt, glib::ObjectExt, ClockExtManual

Implementations

impl Clock

pub const NONE: Option<&'static Clock> = None

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) -> Self

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 HasParamSpec for Clock

type ParamSpec = ParamSpecObject

type SetValue = Clock

Preferred value to be used as setter for the associated ParamSpec.

type BuilderFn = fn(_: &str) -> ParamSpecObjectBuilder<'_, Clock>

fn param_spec_builder() -> Self::BuilderFn

impl Hash for Clock

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

Feeds this value into the given Hasher.

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

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: &Self) -> Ordering

This method returns an Ordering between self and other.

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

Compares and returns the maximum of two values.

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

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Selfwhere
    Self: Sized + PartialOrd<Self>,

Restrict a value to a certain interval.

impl ParentClassIs for Clock

type Parent = Object

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

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

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

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

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

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

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

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

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

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

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

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

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

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

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 Sync for Clock