Bus

Object Hierarchy:

Description:

[ CCode ( type_id = "gst_bus_get_type ()" ) ]
public class Bus : Object

The Bus is an object responsible for delivering Message packets in a first-in first-out way from the streaming threads (see Task) to the application.

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

The GstBus provides support for SignalSource based notifications. This makes it possible to handle the delivery in the glib MainLoop.

The SignalSource callback function async_signal_func can be used to convert all bus messages into signal emissions.

A message is posted on the bus with the post method. With the peek and pop methods one can look at or retrieve a previously posted message.

The bus can be polled with the poll method. This methods blocks up to the specified timeout value until one of the specified messages types is posted on the bus. The application can then pop the messages from the bus to handle them. Alternatively the application can register an asynchronous bus function using add_watch or gst_bus_add_watch. This function will install a SignalSource in the default glib main loop and will deliver messages a short while after they have been posted. Note that the main loop should be running for the asynchronous callbacks.

It is also possible to get messages from the bus without any thread marshalling with the set_sync_handler 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.

Namespace: Gst

Package: gstreamer-1.0

Content:

Properties:

public bool enable_async { construct; }
Enables async message delivery support for bus watches, pop and similar API.

Creation methods:

public Bus ()
Creates a new Bus instance.

Methods:

public void add_signal_watch (int priority = DEFAULT)
Adds a bus signal watch to the default main context with the given priority (e.g. DEFAULT).
public uint add_watch (int priority, owned BusFunc func)
Adds a bus watch to the default main context with the given priority (e.g. DEFAULT).
public bool async_signal_func (Message message, void* data)
A helper BusFunc that can be used to convert all asynchronous messages into signals.
public Source? create_watch ()
Create watch for this bus.
public void disable_sync_message_emission ()
Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
public void enable_sync_message_emission ()
Instructs GStreamer to emit the "sync-message" signal after running the bus's sync handler.
public PollFD get_pollfd ()
Gets the file descriptor from the bus which can be used to get notified about messages being available with functions like poll, and allows integration into other event loops based on file descriptors.
public bool have_pending ()
Checks if there are pending messages on the bus that should be handled.
public Message? peek ()
Peeks the message on the top of the bus' queue.
public Message? poll (MessageType events, ClockTime timeout)
Polls the bus for messages.
public Message? pop ()
Gets a message from the bus.
public Message? pop_filtered (MessageType types)
Gets a message matching type from the bus.
public bool post (owned Message message)
Posts a message on the given bus.
public void remove_signal_watch ()
Removes a signal watch previously added with gst_bus_add_signal_watch.
public bool remove_watch ()
Removes an installed bus watch from this.
public void set_flushing (bool flushing)
If flushing, flushes out and unrefs any messages queued in the bus.
public void set_sync_handler (owned BusSyncHandler? func)
Sets the synchronous handler on the bus.
public BusSyncReply sync_signal_handler (Message message, void* data)
A helper BusSyncHandler that can be used to convert all synchronous messages into signals.
public Message? timed_pop (ClockTime timeout)
Gets a message from the bus, waiting up to the specified timeout.
public Message? timed_pop_filtered (ClockTime timeout, MessageType types)
Gets a message from the bus whose type matches the message type mask types, waiting up to the specified timeout (and discarding any messages that do not match the mask provided).

Signals:

public virtual signal void message (Message message)
A message has been posted on the bus.
public virtual signal void sync_message (Message message)
A message has been posted on the bus.

Inherited Members:

All known members inherited from class Gst.Object

All known members inherited from class GLib.Object