Bus

The #GstBus is an object responsible for delivering #GstMessage packets in a first-in first-out way from the streaming threads (see #GstTask) 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 #GSource based notifications. This makes it possible to handle the delivery in the glib mainloop.

The #GSource callback function gst_bus_async_signal_func() can be used to convert all bus messages into signal emissions.

A message is posted on the bus with the gst_bus_post() method. With the gst_bus_peek() and gst_bus_pop() methods one can look at or retrieve a previously posted message.

The bus can be polled with the gst_bus_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 gst_bus_pop() the messages from the bus to handle them. Alternatively the application can register an asynchronous bus function using gst_bus_add_watch_full() or gst_bus_add_watch(). This function will install a #GSource 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 gst_bus_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 #GstPipeline has one bus.

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

class Bus : ObjectGst {

protected

GstBus* gstBus;

GstBus* getBusStruct(bool transferOwnership);

void* getStruct();

this(GstBus* gstBus, bool ownedRef);

uint addWatch(bool delegate(Message) dlg);

bool delegate(Message) onWatchListener;

static int watchCallBack(GstBus* bus, GstMessage* msg, Bus bus_d);

void setSyncHandler(GstBusSyncReply delegate(Message) dlg);

GstBusSyncReply delegate(Message) onSyncHandlerListener;

static GstBusSyncReply syncHandlerCallBack(GstBus* bus, GstMessage* msg, Bus bus_d);

static GType getType();

this();

void addSignalWatch();

void addSignalWatchFull(int priority);

uint addWatchFull(int priority, GstBusFunc func, void* userData, GDestroyNotify notify);

bool asyncSignalFunc(Message message, void* data);

Source createWatch();

void disableSyncMessageEmission();

void enableSyncMessageEmission();

void getPollfd(GPollFD* fd);

bool havePending();

Message peek();

Message poll(GstMessageType events, GstClockTime timeout);

Message pop();

Message popFiltered(GstMessageType types);

bool post(Message message);

void removeSignalWatch();

bool removeWatch();

void setFlushing(bool flushing);

GstBusSyncReply syncSignalHandler(Message message, void* data);

Message timedPop(GstClockTime timeout);

Message timedPopFiltered(GstClockTime timeout, GstMessageType types);

gulong addOnMessage(void delegate(Message, Bus) dlg, ConnectFlags connectFlags);

gulong addOnSyncMessage(void delegate(Message, Bus) dlg, ConnectFlags connectFlags);

}

Constructors

this this(GstBus* gstBus, bool ownedRef): Sets our main struct and passes it to the parent class.
this this(): Creates a new #GstBus instance.

Members

Functions

addOnMessage gulong addOnMessage(void delegate(Message, Bus) dlg, ConnectFlags connectFlags): A message has been posted on the bus. This signal is emitted from a GSource added to the mainloop. this signal will only be emitted when there is a mainloop running.
addOnSyncMessage gulong addOnSyncMessage(void delegate(Message, Bus) dlg, ConnectFlags connectFlags): A message has been posted on the bus. This signal is emitted from the thread that posted the message so one has to be careful with locking.
addSignalWatch void addSignalWatch(): Adds a bus signal watch to the default main context with the default priority (%G_PRIORITY_DEFAULT). It is also possible to use a non-default main context set up using g_main_context_push_thread_default() (before one had to create a bus watch source and attach it to the desired main context 'manually').
addSignalWatchFull void addSignalWatchFull(int priority): Adds a bus signal watch to the default main context with the given @priority (e.g. %G_PRIORITY_DEFAULT). It is also possible to use a non-default main context set up using g_main_context_push_thread_default() (before one had to create a bus watch source and attach it to the desired main context 'manually').
addWatch uint addWatch(bool delegate(Message) dlg): Adds a bus watch to the default main context with the default priority. This function is used to receive asynchronous messages in the main loop. The watch can be removed using g_source_remove() or by returning FALSE from func. MT safe.
addWatchFull uint addWatchFull(int priority, GstBusFunc func, void* userData, GDestroyNotify notify): Adds a bus watch to the default main context with the given @priority (e.g. %G_PRIORITY_DEFAULT). It is also possible to use a non-default main context set up using g_main_context_push_thread_default() (before one had to create a bus watch source and attach it to the desired main context 'manually').
asyncSignalFunc bool asyncSignalFunc(Message message, void* data): A helper #GstBusFunc that can be used to convert all asynchronous messages into signals.
createWatch Source createWatch(): Create watch for this bus. The GSource will be dispatched whenever a message is on the bus. After the GSource is dispatched, the message is popped off the bus and unreffed.
disableSyncMessageEmission void disableSyncMessageEmission(): Instructs GStreamer to stop emitting the "sync-message" signal for this bus. See gst_bus_enable_sync_message_emission() for more information.
enableSyncMessageEmission void enableSyncMessageEmission(): Instructs GStreamer to emit the "sync-message" signal after running the bus's sync handler. This function is here so that code can ensure that they can synchronously receive messages without having to affect what the bin's sync handler is.
getBusStruct GstBus* getBusStruct(bool transferOwnership): Get the main Gtk struct
getPollfd void getPollfd(GPollFD* fd): Gets the file descriptor from the bus which can be used to get notified about messages being available with functions like g_poll(), and allows integration into other event loops based on file descriptors. Whenever a message is available, the POLLIN / %G_IO_IN event is set.
getStruct void* getStruct(): the main Gtk struct as a void*
havePending bool havePending(): Check if there are pending messages on the bus that should be handled.
peek Message peek(): Peek the message on the top of the bus' queue. The message will remain on the bus' message queue. A reference is returned, and needs to be unreffed by the caller.
poll Message poll(GstMessageType events, GstClockTime timeout): Poll the bus for messages. Will block while waiting for messages to come. You can specify a maximum time to poll with the @timeout parameter. If @timeout is negative, this function will block indefinitely.
pop Message pop(): Get a message from the bus.
popFiltered Message popFiltered(GstMessageType types): Get a message matching @type from the bus. Will discard all messages on the bus that do not match @type and that have been posted before the first message that does match @type. If there is no message matching @type on the bus, all messages will be discarded. It is not possible to use message enums beyond #GST_MESSAGE_EXTENDED in the @events mask.
post bool post(Message message): Post a message on the given bus. Ownership of the message is taken by the bus.
removeSignalWatch void removeSignalWatch(): Removes a signal watch previously added with gst_bus_add_signal_watch().
removeWatch bool removeWatch(): Removes an installed bus watch from @bus.
setFlushing void setFlushing(bool flushing): If @flushing, flush out and unref any messages queued in the bus. Releases references to the message origin objects. Will flush future messages until gst_bus_set_flushing() sets @flushing to %FALSE.
setSyncHandler void setSyncHandler(GstBusSyncReply delegate(Message) dlg): Use this for making an XOverlay. Sets the synchronous handler on the bus. The function will be called every time a new message is posted on the bus. Note that the function will be called in the same thread context as the posting object. This function is usually only called by the creator of the bus. Applications should handle messages asynchronously using the gst_bus watch and poll functions. You cannot replace an existing sync_handler. You can pass NULL to this function, which will clear the existing handler.
syncSignalHandler GstBusSyncReply syncSignalHandler(Message message, void* data): A helper GstBusSyncHandler that can be used to convert all synchronous messages into signals.
timedPop Message timedPop(GstClockTime timeout): Get a message from the bus, waiting up to the specified timeout.
timedPopFiltered Message timedPopFiltered(GstClockTime timeout, GstMessageType types): Get 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).

Static functions

getType GType getType()
syncHandlerCallBack GstBusSyncReply syncHandlerCallBack(GstBus* bus, GstMessage* msg, Bus bus_d): Undocumented in source. Be warned that the author may not have intended to support it.
watchCallBack int watchCallBack(GstBus* bus, GstMessage* msg, Bus bus_d): Undocumented in source. Be warned that the author may not have intended to support it.

Variables

gstBus GstBus* gstBus;: the main Gtk struct
onSyncHandlerListener GstBusSyncReply delegate(Message) onSyncHandlerListener;: Undocumented in source.
onWatchListener bool delegate(Message) onWatchListener;: Undocumented in source.

Inherited Members

From ObjectGst

gstObject GstObject* gstObject;: the main Gtk struct
getObjectGstStruct GstObject* getObjectGstStruct(bool transferOwnership): Get the main Gtk struct
getStruct void* getStruct(): the main Gtk struct as a void*
getType GType getType()
checkUniqueness bool checkUniqueness(ListG list, string name): Checks to see if there is any object named @name in @list. This function does not do any locking of any kind. You might want to protect the provided list with the lock of the owner of the list. This function will lock each #GstObject in the list to compare the name, so be careful when passing a list with a locked object.
defaultDeepNotify void defaultDeepNotify(ObjectG object, ObjectGst orig, ParamSpec pspec, string[] excludedProps): A default deep_notify signal callback for an object. The user data should contain a pointer to an array of strings that should be excluded from the notify. The default handler will print the new value of the property using g_print.
refSink void* refSink(void* object): Increase the reference count of @object, and possibly remove the floating reference, if @object has a floating reference.
replace bool replace(ObjectGst oldobj, ObjectGst newobj): Atomically modifies a pointer to point to a new object. The reference count of @oldobj is decreased and the reference count of @newobj is increased.
addControlBinding bool addControlBinding(ControlBinding binding): Attach the #GstControlBinding to the object. If there already was a #GstControlBinding for this property it will be replaced.
defaultError void defaultError(ErrorG error, string dbg): A default error function that uses g_printerr() to display the error message and the optional debug sting..
getControlBinding ControlBinding getControlBinding(string propertyName): Gets the corresponding #GstControlBinding for the property. This should be unreferenced again after use.
getControlRate GstClockTime getControlRate(): Obtain the control-rate for this @object. Audio processing #GstElement objects will use this rate to sub-divide their processing loop and call gst_object_sync_values() inbetween. The length of the processing segment should be up to @control-rate nanoseconds.
getGValueArray bool getGValueArray(string propertyName, GstClockTime timestamp, GstClockTime interval, Value[] values): Gets a number of #GValues for the given controlled property starting at the requested time. The array @values need to hold enough space for @n_values of #GValue.
getName string getName(): Returns a copy of the name of @object. Caller should g_free() the return value after usage. For a nameless object, this returns %NULL, which you can safely g_free() as well.
getParent ObjectGst getParent(): Returns the parent of @object. This function increases the refcount of the parent object so you should gst_object_unref() it after usage.
getPathString string getPathString(): Generates a string describing the path of @object in the object hierarchy. Only useful (or used) for debugging.
getValue Value getValue(string propertyName, GstClockTime timestamp): Gets the value for the given controlled property at the requested time.
getValueArray bool getValueArray(string propertyName, GstClockTime timestamp, GstClockTime interval, uint nValues, void* values): Gets a number of values for the given controlled property starting at the requested time. The array @values need to hold enough space for @n_values of the same type as the objects property's type.
hasActiveControlBindings bool hasActiveControlBindings(): Check if the @object has active controlled properties.
hasAncestor bool hasAncestor(ObjectGst ancestor): Check if @object has an ancestor @ancestor somewhere up in the hierarchy. One can e.g. check if a #GstElement is inside a #GstPipeline.
hasAsAncestor bool hasAsAncestor(ObjectGst ancestor): Check if @object has an ancestor @ancestor somewhere up in the hierarchy. One can e.g. check if a #GstElement is inside a #GstPipeline.
hasAsParent bool hasAsParent(ObjectGst parent): Check if @parent is the parent of @object. E.g. a #GstElement can check if it owns a given #GstPad.
doref ObjectGst doref(): Increments the reference count on @object. This function does not take the lock on @object because it relies on atomic refcounting.
removeControlBinding bool removeControlBinding(ControlBinding binding): Removes the corresponding #GstControlBinding. If it was the last ref of the binding, it will be disposed.
setControlBindingDisabled void setControlBindingDisabled(string propertyName, bool disabled): This function is used to disable the control bindings on a property for some time, i.e. gst_object_sync_values() will do nothing for the property.
setControlBindingsDisabled void setControlBindingsDisabled(bool disabled): This function is used to disable all controlled properties of the @object for some time, i.e. gst_object_sync_values() will do nothing.
setControlRate void setControlRate(GstClockTime controlRate): Change the control-rate for this @object. Audio processing #GstElement objects will use this rate to sub-divide their processing loop and call gst_object_sync_values() inbetween. The length of the processing segment should be up to @control-rate nanoseconds.
setName bool setName(string name): Sets the name of @object, or gives @object a guaranteed unique name (if @name is %NULL). This function makes a copy of the provided name, so the caller retains ownership of the name it sent.
setParent bool setParent(ObjectGst parent): Sets the parent of @object to @parent. The object's reference count will be incremented, and any floating reference will be removed (see gst_object_ref_sink()).
suggestNextSync GstClockTime suggestNextSync(): Returns a suggestion for timestamps where buffers should be split to get best controller results.
syncValues bool syncValues(GstClockTime timestamp): Sets the properties of the object, according to the #GstControlSources that (maybe) handle them and for the given timestamp.
unparent void unparent(): Clear the parent of @object, removing the associated reference. This function decreases the refcount of @object.
unref void unref(): Decrements the reference count on @object. If reference count hits zero, destroy @object. This function does not take the lock on @object as it relies on atomic refcounting.
addOnDeepNotify gulong addOnDeepNotify(void delegate(ObjectGst, ParamSpec, ObjectGst) dlg, ConnectFlags connectFlags): 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.