Gst.Bin

g GObject.GInterface GObject.GInterface Gst.ChildProxy Gst.ChildProxy GObject.GInterface->Gst.ChildProxy GObject.InitiallyUnowned GObject.InitiallyUnowned Gst.Object Gst.Object GObject.InitiallyUnowned->Gst.Object GObject.Object GObject.Object GObject.Object->GObject.InitiallyUnowned Gst.Bin Gst.Bin Gst.ChildProxy->Gst.Bin Gst.Element Gst.Element Gst.Element->Gst.Bin Gst.Object->Gst.Element

Subclasses

Gst.Pipeline

Methods

Inherited

Gst.Element (81), Gst.Object (27), GObject.Object (37), Gst.ChildProxy (9)

Structs

Gst.ElementClass (10), GObject.ObjectClass (5)

class

new (name)

add (element)

find_unlinked_pad (direction)

get_by_interface (iface)

get_by_name (name)

get_by_name_recurse_up (name)

get_suppressed_flags ()

iterate_all_by_element_factory_name (factory_name)

iterate_all_by_interface (iface)

iterate_elements ()

iterate_recurse ()

iterate_sinks ()

iterate_sorted ()

iterate_sources ()

recalculate_latency ()

remove (element)

set_suppressed_flags (flags)

sync_children_states ()

Virtual Methods

Inherited

Gst.Element (16), Gst.Object (1), GObject.Object (7), Gst.ChildProxy (5)

do_add_element (element)

do_deep_element_added (sub_bin, child)

do_deep_element_removed (sub_bin, child)

do_do_latency ()

do_element_added (child)

do_element_removed (child)

do_handle_message (message)

do_remove_element (element)

Properties

Inherited

Gst.Object (2)

Name

Type

Flags

Short Description

async-handling

bool

r/w

The bin will handle Asynchronous state changes

message-forward

bool

r/w

Forwards all children messages

Signals

Inherited

Gst.Element (3), Gst.Object (1), GObject.Object (1), Gst.ChildProxy (2)

Name

Short Description

deep-element-added

Will be emitted after the element was added to sub_bin.

deep-element-removed

Will be emitted after the element was removed from sub_bin.

do-latency

Will be emitted when the bin needs to perform latency calculations.

element-added

Will be emitted after the element was added to the bin.

element-removed

Will be emitted after the element was removed from the bin.

Fields

Inherited

Gst.Element (3), Gst.Object (1), GObject.Object (1), Gst.ChildProxy (2)

Name

Type

Access

Description

child_bus

Gst.Bus

r

internal bus for handling child messages

children

[Gst.Element]

r

the list of children in this bin

children_cookie

int

r

updated whenever children changes

clock_dirty

bool

r

the bin needs to select a new clock

clock_provider

Gst.Element

r

the element that provided provided_clock

element

Gst.Element

r

messages

[Gst.Message]

r

queued and cached messages

numchildren

int

r

the number of children in this bin

polling

bool

r

the bin is currently calculating its state

provided_clock

Gst.Clock

r

the last clock selected

state_dirty

bool

r

the bin needs to recalculate its state (deprecated)

Class Details

class Gst.Bin(**kwargs)
Bases

Gst.Element, Gst.ChildProxy

Abstract

No

Structure

Gst.BinClass

Gst.Bin is an element that can contain other Gst.Element, allowing them to be managed as a group. Pads from the child elements can be ghosted to the bin, see Gst.GhostPad. This makes the bin look like any other elements and enables creation of higher-level abstraction elements.

A new Gst.Bin is created with Gst.Bin.new(). Use a Gst.Pipeline instead if you want to create a toplevel bin because a normal bin doesn’t have a bus or handle clock distribution of its own.

After the bin has been created you will typically add elements to it with Gst.Bin.add(). You can remove elements with Gst.Bin.remove().

An element can be retrieved from a bin with Gst.Bin.get_by_name(), using the elements name. Gst.Bin.get_by_name_recurse_up() is mainly used for internal purposes and will query the parent bins when the element is not found in the current bin.

An iterator of elements in a bin can be retrieved with Gst.Bin.iterate_elements(). Various other iterators exist to retrieve the elements in a bin.

Gst.Object.unref() is used to drop your reference to the bin.

The Gst.Bin ::element-added signal is fired whenever a new element is added to the bin. Likewise the Gst.Bin ::element-removed signal is fired whenever an element is removed from the bin.

A Gst.Bin internally intercepts every Gst.Message posted by its children and implements the following default behaviour for each of them:

  • Gst.MessageType.EOS: This message is only posted by sinks in the PLAYING state. If all sinks posted the EOS message, this bin will post and EOS message upwards.

  • Gst.MessageType.SEGMENT_START: Just collected and never forwarded upwards. The messages are used to decide when all elements have completed playback of their segment.

  • Gst.MessageType.SEGMENT_DONE: Is posted by Gst.Bin when all elements that posted a SEGMENT_START have posted a SEGMENT_DONE.

  • Gst.MessageType.DURATION_CHANGED: Is posted by an element that detected a change in the stream duration. The duration change is posted to the application so that it can refetch the new duration with a duration query.

    Note that these messages can be posted before the bin is prerolled, in which case the duration query might fail.

    Note also that there might be a discrepancy (due to internal buffering/queueing) between the stream being currently displayed and the returned duration query.

    Applications might want to also query for duration (and changes) by listening to the Gst.MessageType.STREAM_START message, signaling the active start of a (new) stream.

  • Gst.MessageType.CLOCK_LOST: This message is posted by an element when it can no longer provide a clock.

    The default bin behaviour is to check if the lost clock was the one provided by the bin. If so and the bin is currently in the PLAYING state, the message is forwarded to the bin parent.

    This message is also generated when a clock provider is removed from the bin. If this message is received by the application, it should PAUSE the pipeline and set it back to PLAYING to force a new clock distribution.

  • Gst.MessageType.CLOCK_PROVIDE: This message is generated when an element can provide a clock. This mostly happens when a new clock provider is added to the bin.

    The default behaviour of the bin is to mark the currently selected clock as dirty, which will perform a clock recalculation the next time the bin is asked to provide a clock.

    This message is never sent to the application but is forwarded to the parent of the bin.

  • OTHERS: posted upwards.

A Gst.Bin implements the following default behaviour for answering to a Gst.Query:

  • Gst.QueryType.DURATION: The bin will forward the query to all sink elements contained within and will return the maximum value. If no sinks are available in the bin, the query fails.

  • Gst.QueryType.POSITION: The query is sent to all sink elements in the bin and the MAXIMUM of all values is returned. If no sinks are available in the bin, the query fails.

  • OTHERS: the query is forwarded to all sink elements, the result of the first sink that answers the query successfully is returned. If no sink is in the bin, the query fails.

A Gst.Bin will by default forward any event sent to it to all sink ( Gst.EventTypeFlags.DOWNSTREAM ) or source ( Gst.EventTypeFlags.UPSTREAM ) elements depending on the event type.

If all the elements return True, the bin will also return True, else False is returned. If no elements of the required type are in the bin, the event handler will return True.

classmethod new(name)[source]
Parameters

name (str or None) – the name of the new bin

Returns

a new Gst.Bin

Return type

Gst.Element

Creates a new bin with the given name.

add(element)[source]
Parameters

element (Gst.Element) – the Gst.Element to add

Returns

True if the element could be added, False if the bin does not want to accept the element.

Return type

bool

Adds the given element to the bin. Sets the element’s parent, and thus takes ownership of the element. An element can only be added to one bin.

If the element’s pads are linked to other pads, the pads will be unlinked before the element is added to the bin.

When you add an element to an already-running pipeline, you will have to take care to set the state of the newly-added element to the desired state (usually PLAYING or PAUSED, same you set the pipeline to originally) with Gst.Element.set_state(), or use Gst.Element.sync_state_with_parent(). The bin or pipeline will not take care of this for you.

find_unlinked_pad(direction)[source]
Parameters

direction (Gst.PadDirection) – whether to look for an unlinked source or sink pad

Returns

unlinked pad of the given direction.

Return type

Gst.Pad or None

Recursively looks for elements with an unlinked pad of the given direction within the specified bin and returns an unlinked pad if one is found, or None otherwise. If a pad is found, the caller owns a reference to it and should use Gst.Object.unref() on the pad when it is not needed any longer.

get_by_interface(iface)[source]
Parameters

iface (GObject.GType) – the GObject.GType of an interface

Returns

A Gst.Element inside the bin implementing the interface

Return type

Gst.Element or None

Looks for an element inside the bin that implements the given interface. If such an element is found, it returns the element. You can cast this element to the given interface afterwards. If you want all elements that implement the interface, use Gst.Bin.iterate_all_by_interface(). This function recurses into child bins.

get_by_name(name)[source]
Parameters

name (str) – the element name to search for

Returns

the Gst.Element with the given name

Return type

Gst.Element or None

Gets the element with the given name from a bin. This function recurses into child bins.

get_by_name_recurse_up(name)[source]
Parameters

name (str) – the element name to search for

Returns

the Gst.Element with the given name

Return type

Gst.Element or None

Gets the element with the given name from this bin. If the element is not found, a recursion is performed on the parent bin.

get_suppressed_flags()[source]
Returns

the bin’s suppressed Gst.ElementFlags.

Return type

Gst.ElementFlags

New in version 1.10.

iterate_all_by_element_factory_name(factory_name)[source]
Parameters

factory_name (str) – the name of the Gst.ElementFactory

Returns

a Gst.Iterator of Gst.Element for all elements in the bin with the given element factory name

Return type

Gst.Iterator or None

Looks for all elements inside the bin with the given element factory name. The function recurses inside child bins. The iterator will yield a series of Gst.Element.

New in version 1.18.

iterate_all_by_interface(iface)[source]
Parameters

iface (GObject.GType) – the GObject.GType of an interface

Returns

a Gst.Iterator of Gst.Element for all elements in the bin implementing the given interface

Return type

Gst.Iterator or None

Looks for all elements inside the bin that implements the given interface. You can safely cast all returned elements to the given interface. The function recurses inside child bins. The iterator will yield a series of Gst.Element.

iterate_elements()[source]
Returns

a Gst.Iterator of Gst.Element

Return type

Gst.Iterator or None

Gets an iterator for the elements in this bin.

iterate_recurse()[source]
Returns

a Gst.Iterator of Gst.Element

Return type

Gst.Iterator or None

Gets an iterator for the elements in this bin. This iterator recurses into Gst.Bin children.

iterate_sinks()[source]
Returns

a Gst.Iterator of Gst.Element

Return type

Gst.Iterator or None

Gets an iterator for all elements in the bin that have the Gst.ElementFlags.SINK flag set.

iterate_sorted()[source]
Returns

a Gst.Iterator of Gst.Element

Return type

Gst.Iterator or None

Gets an iterator for the elements in this bin in topologically sorted order. This means that the elements are returned from the most downstream elements (sinks) to the sources.

This function is used internally to perform the state changes of the bin elements and for clock selection.

iterate_sources()[source]
Returns

a Gst.Iterator of Gst.Element

Return type

Gst.Iterator or None

Gets an iterator for all elements in the bin that have the Gst.ElementFlags.SOURCE flag set.

recalculate_latency()[source]
Returns

True if the latency could be queried and reconfigured.

Return type

bool

Queries self for the current latency and reconfigures this latency on all the elements using a LATENCY event.

This method is typically called on the pipeline when a Gst.MessageType.LATENCY is posted on the bus.

This function simply emits the Gst.Bin ::do-latency signal so any custom latency calculations will be performed.

remove(element)[source]
Parameters

element (Gst.Element) – the Gst.Element to remove

Returns

True if the element could be removed, False if the bin does not want to remove the element.

Return type

bool

Removes the element from the bin, unparenting it as well. Unparenting the element means that the element will be dereferenced, so if the bin holds the only reference to the element, the element will be freed in the process of removing it from the bin. If you want the element to still exist after removing, you need to call Gst.Object.ref() before removing it from the bin.

If the element’s pads are linked to other pads, the pads will be unlinked before the element is removed from the bin.

set_suppressed_flags(flags)[source]
Parameters

flags (Gst.ElementFlags) – the Gst.ElementFlags to suppress

Suppresses the given flags on the bin. Gst.ElementFlags of a child element are propagated when it is added to the bin. When suppressed flags are set, those specified flags will not be propagated to the bin.

New in version 1.10.

sync_children_states()[source]
Returns

True if syncing the state was successful for all children, otherwise False.

Return type

bool

Synchronizes the state of every child of self with the state of self. See also Gst.Element.sync_state_with_parent().

New in version 1.6.

do_add_element(element) virtual
Parameters

element (Gst.Element) – the element to be added

Returns

True if the element was added

Return type

bool

Method to add an element to the bin.

do_deep_element_added(sub_bin, child) virtual
Parameters

Method called when an element was added somewhere in the bin hierarchy.

do_deep_element_removed(sub_bin, child) virtual
Parameters

Method called when an element was removed somewhere in the bin hierarchy.

do_do_latency() virtual
Return type

bool

do_element_added(child) virtual
Parameters

child (Gst.Element) – the element that was added

Method called when an element was added to the bin.

do_element_removed(child) virtual
Parameters

child (Gst.Element) – the element that was removed

Method called when an element was removed from the bin.

do_handle_message(message) virtual
Parameters

message (Gst.Message) – the message to be handled

Method to handle a message from the children.

do_remove_element(element) virtual
Parameters

element (Gst.Element) – the element to be removed

Returns

True if the element was removed

Return type

bool

Method to remove an element from the bin.

Signal Details

Gst.Bin.signals.deep_element_added(bin, sub_bin, element)
Signal Name

deep-element-added

Flags

RUN_FIRST

Parameters

Will be emitted after the element was added to sub_bin.

New in version 1.10.

Gst.Bin.signals.deep_element_removed(bin, sub_bin, element)
Signal Name

deep-element-removed

Flags

RUN_FIRST

Parameters

Will be emitted after the element was removed from sub_bin.

New in version 1.10.

Gst.Bin.signals.do_latency(bin)
Signal Name

do-latency

Flags

RUN_LAST

Parameters

bin (Gst.Bin) – The object which received the signal

Return type

bool

Will be emitted when the bin needs to perform latency calculations. This signal is only emitted for toplevel bins or when Gst.Bin :async-handling is enabled.

Only one signal handler is invoked. If no signals are connected, the default handler is invoked, which will query and distribute the lowest possible latency to all sinks.

Connect to this signal if the default latency calculations are not sufficient, like when you need different latencies for different sinks in the same pipeline.

Gst.Bin.signals.element_added(bin, element)
Signal Name

element-added

Flags

RUN_FIRST

Parameters

Will be emitted after the element was added to the bin.

Gst.Bin.signals.element_removed(bin, element)
Signal Name

element-removed

Flags

RUN_FIRST

Parameters

Will be emitted after the element was removed from the bin.

Property Details

Gst.Bin.props.async_handling
Name

async-handling

Type

bool

Default Value

False

Flags

READABLE, WRITABLE

If set to True, the bin will handle asynchronous state changes. This should be used only if the bin subclass is modifying the state of its children on its own.

Gst.Bin.props.message_forward
Name

message-forward

Type

bool

Default Value

False

Flags

READABLE, WRITABLE

Forward all children messages, even those that would normally be filtered by the bin. This can be interesting when one wants to be notified of the EOS state of individual elements, for example.

The messages are converted to an ELEMENT message with the bin as the source. The structure of the message is named GstBinForwarded and contains a field named message that contains the original forwarded Gst.Message.