Task

#GstTask is used by #GstElement and #GstPad to provide the data passing threads in a #GstPipeline.

A #GstPad will typically start a #GstTask to push or pull data to/from the peer pads. Most source elements start a #GstTask to push data. In some cases a demuxer element can start a #GstTask to pull data from a peer element. This is typically done when the demuxer can perform random access on the upstream peer element for improved performance.

Although convenience functions exist on #GstPad to start/pause/stop tasks, it might sometimes be needed to create a #GstTask manually if it is not related to a #GstPad.

Before the #GstTask can be run, it needs a #GRecMutex that can be set with gst_task_set_lock().

The task can be started, paused and stopped with gst_task_start(), gst_task_pause() and gst_task_stop() respectively or with the gst_task_set_state() function.

A #GstTask will repeatedly call the #GstTaskFunction with the user data that was provided when creating the task with gst_task_new(). While calling the function it will acquire the provided lock. The provided lock is released when the task pauses or stops.

Stopping a task with gst_task_stop() will not immediately make sure the task is not running anymore. Use gst_task_join() to make sure the task is completely stopped and the thread is stopped.

After creating a #GstTask, use gst_object_unref() to free its resources. This can only be done when the task is not running anymore.

Task functions can send a #GstMessage to send out-of-band data to the application. The application can receive messages from the #GstBus in its mainloop.

For debugging purposes, the task will configure its object name as the thread name on Linux. Please note that the object name should be configured before the task is started; changing the object name after the task has been started, has no effect on the thread name.

class Task : ObjectGst {

protected

GstTask* gstTask;

GstTask* getTaskStruct(bool transferOwnership);

void* getStruct();

this(GstTask* gstTask, bool ownedRef);

static GType getType();

this(GstTaskFunction func, void* userData, GDestroyNotify notify);

static void cleanupAll();

TaskPool getPool();

GstTaskState getState();

bool join();

bool pause();

void setEnterCallback(GstTaskThreadFunc enterFunc, void* userData, GDestroyNotify notify);

void setLeaveCallback(GstTaskThreadFunc leaveFunc, void* userData, GDestroyNotify notify);

void setLock(RecMutex mutex);

void setPool(TaskPool pool);

bool setState(GstTaskState state);

bool start();

bool stop();

}

Constructors

this this(GstTask* gstTask, bool ownedRef): Sets our main struct and passes it to the parent class.
this this(GstTaskFunction func, void* userData, GDestroyNotify notify): Create a new Task that will repeatedly call the provided @func with @user_data as a parameter. Typically the task will run in a new thread.

Members

Functions

getPool TaskPool getPool(): Get the #GstTaskPool that this task will use for its streaming threads.
getState GstTaskState getState(): Get the current state of the task.
getStruct void* getStruct(): the main Gtk struct as a void*
getTaskStruct GstTask* getTaskStruct(bool transferOwnership): Get the main Gtk struct
join bool join(): Joins @task. After this call, it is safe to unref the task and clean up the lock set with gst_task_set_lock().
pause bool pause(): Pauses @task. This method can also be called on a task in the stopped state, in which case a thread will be started and will remain in the paused state. This function does not wait for the task to complete the paused state.
setEnterCallback void setEnterCallback(GstTaskThreadFunc enterFunc, void* userData, GDestroyNotify notify): Call @enter_func when the task function of @task is entered. @user_data will be passed to @enter_func and @notify will be called when @user_data is no longer referenced.
setLeaveCallback void setLeaveCallback(GstTaskThreadFunc leaveFunc, void* userData, GDestroyNotify notify): Call @leave_func when the task function of @task is left. @user_data will be passed to @leave_func and @notify will be called when @user_data is no longer referenced.
setLock void setLock(RecMutex mutex): Set the mutex used by the task. The mutex will be acquired before calling the #GstTaskFunction.
setPool void setPool(TaskPool pool): Set @pool as the new GstTaskPool for @task. Any new streaming threads that will be created by @task will now use @pool.
setState bool setState(GstTaskState state): Sets the state of @task to @state.
start bool start(): Starts @task. The @task must have a lock associated with it using gst_task_set_lock() or this function will return %FALSE.
stop bool stop(): Stops @task. This method merely schedules the task to stop and will not wait for the task to have completely stopped. Use gst_task_join() to stop and wait for completion.

Static functions

cleanupAll void cleanupAll(): Wait for all tasks to be stopped. This is mainly used internally to ensure proper cleanup of internal data structures in test suites.
getType GType getType()

Variables

gstTask GstTask* gstTask;: the main Gtk struct

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.