Gst::Task Class Reference

A class representing GStreamer streaming threads. More...

`#include <gstreamermm/task.h>`

Inheritance diagram for Gst::Task:
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## Public Types

typedef sigc::slot< void > | SlotTask
| For example, void on_do_task();. More...
typedef sigc::slot< void, const Glib::RefPtr< Gst::Task >&, Glib::Threads::Thread* > | TaskThreadSlot
| Bidirectional slot. More...
typedef TaskThreadSlot | SlotEnter
| For example, void on_enter(const Glib::RefPtr<Gst::Task>& task, Glib::Threads::Thread& thread);. More...
typedef TaskThreadSlot | SlotLeave
| For example, void on_leave(const Glib::RefPtr<Gst::Task>& task, Glib::Threads::Thread& thread);. More...

## Public Member Functions

| Task (Task&& src) noexcept
Task& | operator= (Task&& src) noexcept
| ~Task () noexcept override
GstTask* | gobj ()
| Provides access to the underlying C GObject. More...
const GstTask* | gobj () const
| Provides access to the underlying C GObject. More...
GstTask* | gobj_copy ()
| Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs. More...
void | set_lock (Glib::Threads::RecMutex& mutex)
| Set the mutex used by the task. More...
void | set_pool (const Glib::RefPtr< Gst::TaskPool >& pool)
| Set pool as the new GstTaskPool for task. More...
Glib::RefPtr< Gst::TaskPool > | get_pool ()
| Get the Gst::TaskPool that this task will use for its streaming threads. More...
Glib::RefPtr< const Gst::TaskPool > | get_pool () const
| Get the Gst::TaskPool that this task will use for its streaming threads. More...
void | set_enter_slot (const SlotEnter& enter_slot)
| Call enter_slot when the task function of task is entered. More...
void | set_leave_slot (const SlotLeave& leave_slot)
| Call leave_func when the task function of task is left. More...
TaskState | get_state () const
| Get the current state of the task. More...
void | set_state (Gst::TaskState state)
| Sets the state of task to state. More...
bool | pause ()
| Pauses task. More...
bool | start ()
| Starts task. More...
bool | stop ()
| Stops task. More...
bool | join ()
| Joins task. More...
Public Member Functions inherited from Gst::Object
| Object (Object&& src) noexcept
Object& | operator= (Object&& src) noexcept
| ~Object () noexcept override
GstObject* | gobj ()
| Provides access to the underlying C GObject. More...
const GstObject* | gobj () const
| Provides access to the underlying C GObject. More...
GstObject* | gobj_copy ()
| Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs. More...
bool | is_element () const
bool | is_element_factory () const
bool | is_pad () const
bool | is_pad_template () const
bool | is_bin () const
guint32 | get_flags () const
| Returns the entire set of flags for the object. More...
bool | set_name (const Glib::ustring& name)
| Sets the name of object, or gives object a guaranteed unique name (if name is `nullptr`). More...
Glib::ustring | get_name () const
| Returns a copy of the name of object. More...
bool | set_parent (const Glib::RefPtr< Gst::Object >& parent)
| Sets the parent of object to parent. More...
Glib::RefPtr< Gst::Object > | get_parent ()
| Returns the parent of object. More...
Glib::RefPtr< const Gst::Object > | get_parent () const
| Returns the parent of object. More...
void | unparent ()
| Clear the parent of object, removing the associated reference. More...
void | set_control_rate (Gst::ClockTime control_rate)
| Change the control-rate for this object. More...
Gst::ClockTime | get_control_rate () const
| Obtain the control-rate for this object. More...
Gst::ClockTime | suggest_next_sync () const
| Returns a suggestion for timestamps where buffers should be split to get best controller results. More...
bool | sync_values (Gst::ClockTime timestamp)
| Sets the properties of the object, according to the Gst::ControlSources that (maybe) handle them and for the given timestamp. More...
void | set_control_bindings_disabled (bool disabled)
| This function is used to disable all controlled properties of the object for some time, i.e. sync_values() will do nothing. More...
bool | has_asctive_control_bindings () const
| Check if the object has an active controlled properties. More...
bool | has_ancestor (const Glib::RefPtr< const Gst::Object >& ancestor) const
| Check if object has an ancestor ancestor somewhere up in the hierarchy. More...
bool | has_as_ancestor (const Glib::RefPtr< Gst::Object >& ancestor) const
| Check if object has an ancestor ancestor somewhere up in the hierarchy. More...
bool | has_as_parent (const Glib::RefPtr< Gst::Object >& parent) const
| Check if parent is the parent of object. More...
Glib::ustring | get_path_string ()
| Generates a string describing the path of object in the object hierarchy. More...
Glib::PropertyProxy< Glib::ustring > | property_name ()
| The name of the object. More...
Glib::PropertyProxy_ReadOnly< Glib::ustring > | property_name () const
| The name of the object. More...
Glib::PropertyProxy< Glib::RefPtr< Gst::Object > > | property_parent ()
| The parent of the object. More...
Glib::PropertyProxy_ReadOnly< Glib::RefPtr< Gst::Object > > | property_parent () const
| The parent of the object. More...
Glib::SignalProxy< void, const Glib::RefPtr< Gst::Object >&, GParamSpec*> | signal_deep_notify ()
int | get_refcount () const

## Static Public Member Functions

static GType | get_type ()
| Get the GType for this class, for use with the underlying GObject type system. More...
static Glib::RefPtr< Task > | create (const SlotTask& task_slot)
| Create a new Gst::Task that will repeatedly call the provided slot as a parameter. More...
static void | cleanup_all ()
| Wait for all tasks to be stopped. More...
Static Public Member Functions inherited from Gst::Object
static GType | get_type ()
| Get the GType for this class, for use with the underlying GObject type system. More...
static bool | check_uniqueness (const Glib::ListHandle< const Gst::Object >& list, const Glib::ustring& name)
| Checks to see if there is any object named name in list. More...

## Protected Member Functions

| Task (const SlotTask& task_slot)
Protected Member Functions inherited from Gst::Object
virtual void | on_deep_notify (const Glib::RefPtr< Gst::Object >& prop_object, GParamSpec* prop)
| This is a default handler for the signal signal_deep_notify(). More...

## Related Functions

(Note that these are not member functions.)
Glib::RefPtr< Gst::Task > | wrap (GstTask* object, bool take_copy=false)
| A Glib::wrap() method for this object. More...
Related Functions inherited from Gst::Object
Glib::RefPtr< Gst::Object > | wrap (GstObject* object, bool take_copy=false)
| A Glib::wrap() method for this object. More...

## Detailed Description

A class representing GStreamer streaming threads.

Gst::Task is used by Gst::Element and Gst::Pad to provide the data passing threads in a Gst::Pipeline.

A Gst::Pad will typically start a Gst::Task to push or pull data to/from the peer pads. Most source elements start a Gst::Task to push data. In some cases a demuxer element can start a Gst::Task 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 Gst::Pad to start/pause/stop tasks, it might sometimes be needed to create a Gst::Task manually if it is not related to a Gst::Pad.

Before the Gst::Task can be run, it needs a Glib::StaticRecMutex that can be set with set_lock().

The task can be started, paused and stopped with start(), pause() and stop() respectively.

A Gst::Task will repeadedly call the Gst::Task::SlotTask that was provided when creating the task with create(). Before calling the function it will acquire the provided lock.

Stopping a task with stop() will not immediatly make sure the task is not running anymore. Use join() to make sure the task is completely stopped and the thread is stopped.

Task functions can send a Gst::Message to send out-of-band data to the application. The application can receive messages from the Gst::Bus 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.

Last reviewed on 2015-10-14 (1.5.2)

## Member Typedef Documentation

## SlotEnter

typedef TaskThreadSlot Gst::Task::SlotEnter

For example, void on_enter(const Glib::RefPtr<Gst::Task>& task, Glib::Threads::Thread& thread);.

A thread is entered, this slot is called when the new thread enters its function.

## SlotLeave

typedef TaskThreadSlot Gst::Task::SlotLeave

For example, void on_leave(const Glib::RefPtr<Gst::Task>& task, Glib::Threads::Thread& thread);.

A thread is exiting, this is called when the thread is about to leave its function.

## SlotTask

typedef sigc::slot<void> Gst::Task::SlotTask

For example, void on_do_task();.

## TaskThreadSlot

typedef sigc::slot<void, const Glib::RefPtr<Gst::Task>&, Glib::Threads::Thread*> Gst::Task::TaskThreadSlot

Bidirectional slot.

## Constructor & Destructor Documentation

## Task() [1/2]

Gst::Task::Task | ( | Task&& | src | ) |

noexcept

## ~Task()

Gst::Task::~Task | ( |  | ) |

override noexcept

## Task() [2/2]

Gst::Task::Task | ( | const SlotTask& | task_slot | ) |

explicit protected

## Member Function Documentation

## cleanup_all()

static void Gst::Task::cleanup_all | ( |  | ) |

static

Wait for all tasks to be stopped.

This is mainly used internally to ensure proper cleanup of internal data structures in test suites.

MT safe.

## create()

static Glib::RefPtr<Task> Gst::Task::create | ( | const SlotTask& | task_slot | ) |

static

Create a new Gst::Task that will repeatedly call the provided slot as a parameter.

Typically the task will run in a new thread.

The slot cannot be changed after the task has been created. You must create a new Gst::Task to change the slot.

Parameters

  task_slot | The Gst::Task::SlotTask to use.

Returns
  A new Gst::Task. MT safe.

## get_pool() [1/2]

Glib::RefPtr<Gst::TaskPool> Gst::Task::get_pool | ( |  | ) |

Get the Gst::TaskPool that this task will use for its streaming threads.

MT safe.

Returns
  The Gst::TaskPool used by task. Gst::Object::unref() after usage.

## get_pool() [2/2]

Glib::RefPtr<const Gst::TaskPool> Gst::Task::get_pool | ( |  | ) | const

Get the Gst::TaskPool that this task will use for its streaming threads.

MT safe.

Returns
  The Gst::TaskPool used by task. Gst::Object::unref() after usage.

## get_state()

TaskState Gst::Task::get_state | ( |  | ) | const

Get the current state of the task.

Returns
  The Gst::TaskState of the task

MT safe.

## get_type()

static GType Gst::Task::get_type | ( |  | ) |

static

Get the GType for this class, for use with the underlying GObject type system.

## gobj() [1/2]

GstTask* Gst::Task::gobj | ( |  | ) |

inline

Provides access to the underlying C GObject.

## gobj() [2/2]

const GstTask* Gst::Task::gobj | ( |  | ) | const

inline

Provides access to the underlying C GObject.

## gobj_copy()

GstTask* Gst::Task::gobj_copy | ( |  | ) |

Provides access to the underlying C instance. The caller is responsible for unrefing it. Use when directly setting fields in structs.

## join()

bool Gst::Task::join | ( |  | ) |

Joins task.

After this call, it is safe to unref the task and clean up the lock set with set_lock().

The task will automatically be stopped with this call.

This function cannot be called from within a task function as this would cause a deadlock. The function will detect this and print a g_warning.

Returns
  `true` if the task could be joined.

MT safe.

## operator=()

Task& Gst::Task::operator= | ( | Task&& | src | ) |

noexcept

## pause()

bool Gst::Task::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.

Returns
  `true` if the task could be paused.

MT safe.

## set_enter_slot()

void Gst::Task::set_enter_slot | ( | const SlotEnter& | enter_slot | ) |

Call enter_slot when the task function of task is entered.

Parameters

  enter_slot |

## set_leave_slot()

void Gst::Task::set_leave_slot | ( | const SlotLeave& | leave_slot | ) |

Call leave_func when the task function of task is left.

Parameters

  leave_slot |

## set_lock()

void Gst::Task::set_lock | ( | Glib::Threads::RecMutex & | mutex | ) |

Set the mutex used by the task.

The mutex will be acquired before calling the Gst::TaskFunction.

This function has to be called before calling pause() or start().

MT safe.

Parameters

  mutex | The RecMutex to use.

## set_pool()

void Gst::Task::set_pool | ( | const Glib::RefPtr< Gst::TaskPool >& | pool | ) |

Set pool as the new GstTaskPool for task.

Any new streaming threads that will be created by task will now use pool.

MT safe.

Parameters

  pool | A Gst::TaskPool.

## set_state()

void Gst::Task::set_state | ( | Gst::TaskState | state | ) |

Sets the state of task to state.

The task must have a lock associated with it using set_lock() when going to GST_TASK_STARTED or GST_TASK_PAUSED or this function will return `false`.

MT safe.

Parameters

  state | The new task state.

Returns
  `true` if the state could be changed.

## start()

bool Gst::Task::start | ( |  | ) |

Starts task.

The task must have a lock associated with it using set_lock() or this function will return `false`.

Returns
  `true` if the task could be started.

MT safe.

## stop()

bool Gst::Task::stop | ( |  | ) |

Stops task.

This method merely schedules the task to stop and will not wait for the task to have completely stopped. Use join() to stop and wait for completion.

Returns
  `true` if the task could be stopped.

MT safe.

## Friends And Related Function Documentation

## wrap()

Glib::RefPtr< Gst::Task > wrap | ( | GstTask * | object,
|  | bool | take_copy = `false`
| ) |  |

related

A Glib::wrap() method for this object.

Parameters

  object | The C instance.
  take_copy | False if the result should take ownership of the C instance. True if it should take a new copy or ref.

Returns
  A C++ instance that wraps this C instance.