org.freedesktop.gstreamer

Class Bus

java.lang.Object

org.freedesktop.gstreamer.glib.NativeObject

org.freedesktop.gstreamer.glib.RefCountedObject

org.freedesktop.gstreamer.glib.GObject

org.freedesktop.gstreamer.GstObject

org.freedesktop.gstreamer.Bus

All Implemented Interfaces:

AutoCloseable

public class Bus
extends GstObject

The Bus is an object responsible for delivering Messages in a first-in first-out way from the streaming threads to the application.

See upstream documentation at https://gstreamer.freedesktop.org/documentation/gstreamer/gstbus.html

Since the application typically only wants to deal with delivery of these messages from one thread, the Bus will marshal the messages between different threads. This is important since the actual streaming of media is done in another thread than the application.

It is also possible to get messages from the bus without any thread marshalling with the setSyncHandler(org.freedesktop.gstreamer.BusSyncHandler) method. This makes it possible to react to a message in the same thread that posted the message on the bus. This should only be used if the application is able to deal with messages from different threads.

Every Pipeline has one bus.

Note that a Pipeline will set its bus into flushing state when changing from READY to NULL state.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	Bus.ASYNC_DONE Signal emitted by elements when they complete an ASYNC state change.
static interface	Bus.BUFFERING Signal emitted when the pipeline is buffering data.
static interface	Bus.DURATION_CHANGED Signal sent when a new duration message is posted by an element that know the duration of a stream in a specific format.
static interface	Bus.EOS Signal emitted when end-of-stream is reached in a pipeline.
static interface	Bus.ERROR Signal emitted when an error occurs.
static interface	Bus.INFO Signal emitted when an informational message is delivered.
static interface	Bus.MESSAGE Catch all signals emitted on the Bus.
static interface	Bus.SEGMENT_DONE Signal emitted when the pipeline has completed playback of a segment.
static interface	Bus.SEGMENT_START This message is posted by elements that start playback of a segment as a result of a segment seek.
static interface	Bus.STATE_CHANGED Signal emitted when a state change happens.
static interface	Bus.TAG Signal emitted when a new tag is identified on the stream.
static interface	Bus.WARNING Signal emitted when a warning message is delivered.

Nested classes/interfaces inherited from class org.freedesktop.gstreamer.GstObject

GstObject.Handle

Nested classes/interfaces inherited from class org.freedesktop.gstreamer.glib.GObject

GObject.GCallback, GObject.GInterface

Nested classes/interfaces inherited from class org.freedesktop.gstreamer.glib.NativeObject

NativeObject.Initializer, NativeObject.TypeProvider, NativeObject.TypeRegistration<T extends NativeObject>

Field Summary

Fields

Modifier and Type	Field and Description
static String	GTYPE_NAME

Method Summary

Modifier and Type	Method and Description
void	clearSyncHandler() Clear the synchronous handler.
void	connect(Bus.ASYNC_DONE listener) Add a listener for Bus.ASYNC_DONE messages in the Pipeline.
void	connect(Bus.BUFFERING listener) Add a listener for Bus.BUFFERING messages in the Pipeline.
void	connect(Bus.DURATION_CHANGED listener) Add a listener for duration changes.
void	connect(Bus.EOS listener) Add a listener for end-of-stream messages.
void	connect(Bus.ERROR listener) Add a listener for error messages.
void	connect(Bus.INFO listener) Add a listener for informational messages.
void	connect(Bus.MESSAGE listener) Add a listener for all messages posted on the Bus.
void	connect(Bus.SEGMENT_DONE listener) Add a listener for Bus.SEGMENT_DONE messages in the Pipeline.
void	connect(Bus.SEGMENT_START listener) Add a listener for Bus.SEGMENT_START messages in the Pipeline.
void	connect(Bus.STATE_CHANGED listener) Add a listener for State changes in the Pipeline.
void	connect(Bus.TAG listener) Add a listener for new media tags.
void	connect(Bus.WARNING listener) Add a listener for warning messages.
void	connect(String signal, Bus.MESSAGE listener) Add a listener for messages of type signal posted on the Bus.
<T> void	connect(String signal, Class<T> listenerClass, T listener, com.sun.jna.Callback callback) Connects a callback to a signal.
void	disconnect(Bus.ASYNC_DONE listener) Disconnect the listener for async-done messages.
void	disconnect(Bus.BUFFERING listener) Disconnect the listener for buffering messages.
void	disconnect(Bus.DURATION_CHANGED listener) Disconnect the listener for duration change messages.
void	disconnect(Bus.EOS listener) Disconnect the listener for end-of-stream messages.
void	disconnect(Bus.ERROR listener) Disconnect the listener for error messages.
void	disconnect(Bus.INFO listener) Disconnect the listener for informational messages.
void	disconnect(Bus.MESSAGE listener) Disconnect the listener for segment-done messages.
void	disconnect(Bus.SEGMENT_DONE listener) Disconnect the listener for segment-done messages.
void	disconnect(Bus.SEGMENT_START listener) Disconnect the listener for segment-start messages.
void	disconnect(Bus.STATE_CHANGED listener) Disconnect the listener for State change messages.
void	disconnect(Bus.TAG listener) Disconnect the listener for tag messages.
void	disconnect(Bus.WARNING listener) Disconnect the listener for warning messages.
<T> void	disconnect(Class<T> listenerClass, T listener)
void	dispose() Dispose this object, and potentially clear (free, unref, etc.) the underlying native object if this object owns the reference.
BusSyncHandler	getSyncHandler() Get the current synchronous handler.
boolean	post(Message message) Posts a Message on this Bus.
void	setFlushing(boolean flushing) Instructs the bus to flush out any queued messages.
void	setSyncHandler(BusSyncHandler handler) Sets the synchronous handler (message listener) on the bus.

Methods inherited from class org.freedesktop.gstreamer.GstObject

addControlBinding, getAsString, getControlBinding, getName, getParent, hasActiveControlBindings, removeControlBinding, setAsString, setControlBindingDisabled, setControlBindingsDisabled, setName, suggestNextSync, syncValues, toString

Methods inherited from class org.freedesktop.gstreamer.glib.GObject

addCallback, connect, emit, emit, get, getPropertyDefaultValue, getPropertyMaximumValue, getPropertyMinimumValue, getRefCount, getTypeName, invalidate, listPropertyNames, removeCallback, set

Methods inherited from class org.freedesktop.gstreamer.glib.NativeObject

close, disown, equals, getPointer, getRawPointer, hashCode

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

GTYPE_NAME

public static final String GTYPE_NAME

See Also:

Constant Field Values

Method Detail

setFlushing

public void setFlushing(boolean flushing)

Instructs the bus to flush out any queued messages. If flushing, flush out any messages queued in the bus. Will flush future messages until setFlushing(boolean) is called with false.

Parameters:

flushing - true if flushing is desired.

connect

public void connect(Bus.EOS listener)

Add a listener for end-of-stream messages.

Parameters:

listener - The listener to be called when end-of-stream is encountered.

disconnect

public void disconnect(Bus.EOS listener)

Disconnect the listener for end-of-stream messages.

Parameters:

listener - The listener that was registered to receive the message.

connect

public void connect(Bus.ERROR listener)

Add a listener for error messages.

Parameters:

listener - The listener to be called when an error in the stream is encountered.

disconnect

public void disconnect(Bus.ERROR listener)

Disconnect the listener for error messages.

Parameters:

listener - The listener that was registered to receive the message.

connect

public void connect(Bus.WARNING listener)

Add a listener for warning messages.

Parameters:

listener - The listener to be called when an Element emits a warning.

disconnect

public void disconnect(Bus.WARNING listener)

Disconnect the listener for warning messages.

Parameters:

listener - The listener that was registered to receive the message.

connect

public void connect(Bus.INFO listener)

Add a listener for informational messages.

Parameters:

listener - The listener to be called when an Element emits a an informational message.

disconnect

public void disconnect(Bus.INFO listener)

Disconnect the listener for informational messages.

Parameters:

listener - The listener that was registered to receive the message.

connect

public void connect(Bus.STATE_CHANGED listener)

Add a listener for State changes in the Pipeline.

Parameters:

listener - The listener to be called when the Pipeline changes state.

disconnect

public void disconnect(Bus.STATE_CHANGED listener)

Disconnect the listener for State change messages.

Parameters:

listener - The listener that was registered to receive the message.

connect

public void connect(Bus.TAG listener)

Add a listener for new media tags.

Parameters:

listener - The listener to be called when new media tags are found.

disconnect

public void disconnect(Bus.TAG listener)

Disconnect the listener for tag messages.

Parameters:

listener - The listener that was registered to receive the message.

connect

public void connect(Bus.BUFFERING listener)

Add a listener for Bus.BUFFERING messages in the Pipeline.

Parameters:

listener - The listener to be called when the Pipeline buffers data.

disconnect

public void disconnect(Bus.BUFFERING listener)

Disconnect the listener for buffering messages.

Parameters:

listener - The listener that was registered to receive the message.

connect

public void connect(Bus.DURATION_CHANGED listener)

Add a listener for duration changes.

Parameters:

listener - The listener to be called when the duration changes.

disconnect

public void disconnect(Bus.DURATION_CHANGED listener)

Disconnect the listener for duration change messages.

Parameters:

listener - The listener that was registered to receive the message.

connect

public void connect(Bus.SEGMENT_START listener)

Add a listener for Bus.SEGMENT_START messages in the Pipeline.

Parameters:

listener - The listener to be called when the Pipeline has started a segment.

disconnect

public void disconnect(Bus.SEGMENT_START listener)

Disconnect the listener for segment-start messages.

Parameters:

listener - The listener that was registered to receive the message.

connect

public void connect(Bus.SEGMENT_DONE listener)

Add a listener for Bus.SEGMENT_DONE messages in the Pipeline.

Parameters:

listener - The listener to be called when the Pipeline has finished a segment.

disconnect

public void disconnect(Bus.SEGMENT_DONE listener)

Disconnect the listener for segment-done messages.

Parameters:

listener - The listener that was registered to receive the message.

connect

public void connect(Bus.ASYNC_DONE listener)

Add a listener for Bus.ASYNC_DONE messages in the Pipeline.

Parameters:

listener - The listener to be called when the an element has finished an async state change.

disconnect

public void disconnect(Bus.ASYNC_DONE listener)

Disconnect the listener for async-done messages.

Parameters:

listener - The listener that was registered to receive the message.

connect

public void connect(Bus.MESSAGE listener)

Add a listener for all messages posted on the Bus.

Parameters:

listener - The listener to be called when a Message is posted.

connect

public void connect(String signal,
                    Bus.MESSAGE listener)

Add a listener for messages of type signal posted on the Bus.

Parameters:

signal - the signal to connect to.

listener - The listener to be called when a Message is posted.

disconnect

public void disconnect(Bus.MESSAGE listener)

Disconnect the listener for segment-done messages.

Parameters:

listener - The listener that was registered to receive the message.

post

public boolean post(Message message)

Posts a Message on this Bus.

Parameters:

message - the message to post.

Returns:

true if the message could be posted, false if the bus is flushing.

setSyncHandler

public void setSyncHandler(BusSyncHandler handler)

Sets the synchronous handler (message listener) on the bus. The handler will be called every time a new message is posted on the bus. Note that the handler will be called in the same thread context as the posting object. Applications should generally handle messages asynchronously using the other message listeners.

Only one handler may be attached to the bus at any one time. An attached sync handler forces creation of Message objects for all messages on the bus, so the handler should be removed if no longer required.

A single native sync handler is used at all times, with synchronous and asynchronous dispatch handled on the Java side, so the bindings do not inherit issues in clearing or replacing the sync handler with versions of GStreamer prior to 1.16.3.

Parameters:

handler - bus sync handler, or null to remove

clearSyncHandler

public void clearSyncHandler()

Clear the synchronous handler.

This is a convenience method equivalent to setSyncHandler(null)

getSyncHandler

public BusSyncHandler getSyncHandler()

Get the current synchronous handler.

Returns:

current sync handler, or null

connect

public <T> void connect(String signal,
                        Class<T> listenerClass,
                        T listener,
                        com.sun.jna.Callback callback)

Connects a callback to a signal.

This differs to GObject#connect in that it hooks up Bus signals to the sync callback, not the generic GObject signal mechanism.

Overrides:

connect in class GObject

Type Parameters:

T - listener type

Parameters:

signal - the name of the signal to connect to.

listenerClass - the class of the listener

listener - the listener to associate with the callback

callback - the callback to call when the signal is emitted.

disconnect

public <T> void disconnect(Class<T> listenerClass,
                           T listener)

Overrides:

disconnect in class GObject

dispose

public void dispose()

Description copied from class: NativeObject

Dispose this object, and potentially clear (free, unref, etc.) the underlying native object if this object owns the reference.

After calling this method this object should not be used.

Overrides:

dispose in class GObject