Gst.Bin

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

Subclasses:Gst.Pipeline

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.

Notes

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 default bin behaviour is to clear any cached duration values so that the next duration query will perform a full duration recalculation. 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.
  • 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 tot 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 :If the query has been asked before with the same format and the bin is a toplevel bin (ie. has no parent), use the cached previous value. If no previous value was cached, the query is sent to all sink elements in the bin and the MAXIMUM of all values is returned. If the bin is a toplevel bin the value is cached. 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.

MT safe.

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, None.
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

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.

MT safe. Caller owns returned reference.

get_by_name(name)[source]
Parameters:name (str) – the element name to search for
Returns:the Gst.Element with the given name, or None
Return type:Gst.Element or None

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

Returns None if no element with the given name is found in the bin.

MT safe. Caller owns returned reference.

get_by_name_recurse_up(name)[source]
Parameters:name (str) – the element name to search for
Returns:the Gst.Element with the given name, or None
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.

Returns None if:

  • no element with the given name is found in the bin

MT safe. Caller owns returned reference.

get_suppressed_flags()[source]
Returns:the bin’s suppressed Gst.ElementFlags.
Return type:Gst.ElementFlags

Return the suppressed flags of the bin.

MT safe.

New in version 1.10.

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, or None
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 that should be unreffed after use.

MT safe. Caller owns returned value.

iterate_elements()[source]
Returns:a Gst.Iterator of Gst.Element, or None
Return type:Gst.Iterator or None

Gets an iterator for the elements in this bin.

MT safe. Caller owns returned value.

iterate_recurse()[source]
Returns:a Gst.Iterator of Gst.Element, or None
Return type:Gst.Iterator or None

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

MT safe. Caller owns returned value.

iterate_sinks()[source]
Returns:a Gst.Iterator of Gst.Element, or None
Return type:Gst.Iterator or None

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

MT safe. Caller owns returned value.

iterate_sorted()[source]
Returns:a Gst.Iterator of Gst.Element, or None
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.

MT safe. Caller owns returned value.

iterate_sources()[source]
Returns:a Gst.Iterator of Gst.Element, or None
Return type:Gst.Iterator or None

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

MT safe. Caller owns returned value.

recalculate_latency()[source]
Returns:True if the latency could be queried and reconfigured.
Return type:bool

Query self for the current latency using and reconfigures this latency to all the elements with 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 ‘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.

MT safe.

set_suppressed_flags(flags)[source]
Parameters:flags (Gst.ElementFlags) – the Gst.ElementFlags to suppress

Suppress 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.

MT safe.

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) –
Return type:bool
do_deep_element_added(sub_bin, child) virtual
Parameters:
do_deep_element_removed(sub_bin, child) virtual
Parameters:
do_do_latency() virtual
Return type:bool
do_element_added(child) virtual
Parameters:child (Gst.Element) –
do_element_removed(child) virtual
Parameters:child (Gst.Element) –
do_handle_message(message) virtual
Parameters:message (Gst.Message) –
do_remove_element(element) virtual
Parameters:element (Gst.Element) –
Return type:bool

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 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’ of type GST_TYPE_MESSAGE that contains the original forwarded message.