GstObject

GstObject — Base class for the GStreamer object hierarchy

Functions

Properties

gchar * name Read / Write / Construct
GstObject * parent Read / Write

Signals

void deep-notify No Hooks

Types and Values

Object Hierarchy

    GObject
    ╰── GInitiallyUnowned
        ╰── GstObject
            ├── GstAllocator
            ├── GstPad
            ├── GstPadTemplate
            ├── GstPluginFeature
            ├── GstElement
            ├── GstBus
            ├── GstTask
            ├── GstTaskPool
            ├── GstClock
            ├── GstControlBinding
            ├── GstControlSource
            ├── GstPlugin
            ╰── GstRegistry

Includes

#include <gst/gst.h>

Description

GstObject provides a root for the object hierarchy tree filed in by the GStreamer library. It is currently a thin wrapper on top of GInitiallyUnowned. It is an abstract class that is not very usable on its own.

GstObject gives us basic refcounting, parenting functionality and locking. Most of the function are just extended for special GStreamer needs and can be found under the same name in the base class of GstObject which is GObject (e.g. g_object_ref() becomes gst_object_ref()).

Since GstObject dereives from GInitiallyUnowned, it also inherits the floating reference. Be aware that functions such as gst_bin_add() and gst_element_add_pad() take ownership of the floating reference.

In contrast to GObject instances, GstObject adds a name property. The functions gst_object_set_name() and gst_object_get_name() are used to set/get the name of the object.

controlled properties

Controlled properties offers a lightweight way to adjust gobject properties over stream-time. It works by using time-stamped value pairs that are queued for element-properties. At run-time the elements continuously pull values changes for the current stream-time. What needs to be changed in a GstElement? Very little - it is just two steps to make a plugin controllable!

  1. mark gobject-properties paramspecs that make sense to be controlled, by GST_PARAM_CONTROLLABLE.

  2. when processing data (get, chain, loop function) at the beginning call gst_object_sync_values(element,timestamp). This will made the controller to update all gobject properties that are under control with the current values based on timestamp.

What needs to be done in applications? Again it's not a lot to change.

  1. create a GstControlSource. csource = gst_interpolation_control_source_new(); g_object_set (csource, "mode", GST_INTERPOLATION_MODE_LINEAR, NULL);

  2. Attach the GstControlSource on the controller to a property. gst_object_add_control_binding (object, gst_direct_control_binding_new (object, "prop1", csource));

  3. Set the control values gst_timed_value_control_source_set ((GstTimedValueControlSource *)csource,0 * GST_SECOND, value1); gst_timed_value_control_source_set ((GstTimedValueControlSource *)csource,1 * GST_SECOND, value2);

  4. start your pipeline

Last reviewed on 2012-03-29 (0.11.3)

Functions

GST_OBJECT_FLAGS()

#define GST_OBJECT_FLAGS(obj)                  (GST_OBJECT_CAST (obj)->flags)

This macro returns the entire set of flags for the object.

Parameters

obj

a GstObject

 

GST_OBJECT_FLAG_IS_SET()

#define GST_OBJECT_FLAG_IS_SET(obj,flag)       ((GST_OBJECT_FLAGS (obj) & (flag)) == (flag))

This macro checks to see if the given flag is set.

Parameters

obj

a GstObject

 

flag

Flag to check for

 

GST_OBJECT_FLAG_SET()

#define GST_OBJECT_FLAG_SET(obj,flag)          (GST_OBJECT_FLAGS (obj) |= (flag))

This macro sets the given bits.

Parameters

obj

a GstObject

 

flag

Flag to set

 

GST_OBJECT_FLAG_UNSET()

#define GST_OBJECT_FLAG_UNSET(obj,flag)        (GST_OBJECT_FLAGS (obj) &= ~(flag))

This macro usets the given bits.

Parameters

obj

a GstObject

 

flag

Flag to set

 

GST_OBJECT_NAME()

#define GST_OBJECT_NAME(obj)            (GST_OBJECT_CAST(obj)->name)

Get the name of this object

Parameters

obj

a GstObject

 

GST_OBJECT_PARENT()

#define GST_OBJECT_PARENT(obj)          (GST_OBJECT_CAST(obj)->parent)

Get the parent of this object

Parameters

obj

a GstObject

 

GST_OBJECT_REFCOUNT()

#define GST_OBJECT_REFCOUNT(obj)                (((GObject*)(obj))->ref_count)

Get access to the reference count field of the object.

Parameters

obj

a GstObject

 

GST_OBJECT_REFCOUNT_VALUE()

#define GST_OBJECT_REFCOUNT_VALUE(obj)          g_atomic_int_get ((gint *) &GST_OBJECT_REFCOUNT(obj))

Get the reference count value of the object.

Parameters

obj

a GstObject

 

GST_OBJECT_LOCK()

#define GST_OBJECT_LOCK(obj)                   g_mutex_lock(GST_OBJECT_GET_LOCK(obj))

This macro will obtain a lock on the object, making serialization possible. It blocks until the lock can be obtained.

Parameters

obj

a GstObject to lock

 

GST_OBJECT_TRYLOCK()

#define GST_OBJECT_TRYLOCK(obj)                g_mutex_trylock(GST_OBJECT_GET_LOCK(obj))

This macro will try to obtain a lock on the object, but will return with FALSE if it can't get it immediately.

Parameters

obj

a GstObject.

 

GST_OBJECT_UNLOCK()

#define GST_OBJECT_UNLOCK(obj)                 g_mutex_unlock(GST_OBJECT_GET_LOCK(obj))

This macro releases a lock on the object.

Parameters

obj

a GstObject to unlock.

 

GST_OBJECT_GET_LOCK()

#define GST_OBJECT_GET_LOCK(obj)               (&GST_OBJECT_CAST(obj)->lock)

Acquire a reference to the mutex of this object.

Parameters

obj

a GstObject

 

gst_object_set_name ()

gboolean
gst_object_set_name (GstObject *object,
                     const gchar *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.

Parameters

object

a GstObject

 

name

new name of object

 

Returns

TRUE if the name could be set. Since Objects that have a parent cannot be renamed, this function returns FALSE in those cases.

MT safe. This function grabs and releases object 's LOCK.


gst_object_get_name ()

gchar *
gst_object_get_name (GstObject *object);

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.

Free-function: g_free

Parameters

object

a GstObject

 

Returns

the name of object . g_free() after usage.

MT safe. This function grabs and releases object 's LOCK.

[transfer full]


gst_object_set_parent ()

gboolean
gst_object_set_parent (GstObject *object,
                       GstObject *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()).

Parameters

object

a GstObject

 

parent

new parent of object

 

Returns

TRUE if parent could be set or FALSE when object already had a parent or object and parent are the same.

MT safe. Grabs and releases object 's LOCK.


gst_object_get_parent ()

GstObject *
gst_object_get_parent (GstObject *object);

Returns the parent of object . This function increases the refcount of the parent object so you should gst_object_unref() it after usage.

Parameters

object

a GstObject

 

Returns

parent of object , this can be NULL if object has no parent. unref after usage.

MT safe. Grabs and releases object 's LOCK.

[transfer full]


gst_object_unparent ()

void
gst_object_unparent (GstObject *object);

Clear the parent of object , removing the associated reference. This function decreases the refcount of object .

MT safe. Grabs and releases object 's lock.

Parameters

object

a GstObject to unparent

 

gst_object_default_deep_notify ()

void
gst_object_default_deep_notify (GObject *object,
                                GstObject *orig,
                                GParamSpec *pspec,
                                gchar **excluded_props);

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.

MT safe. This function grabs and releases object 's LOCK for getting its path string.

Parameters

object

the GObject that signalled the notify.

 

orig

a GstObject that initiated the notify.

 

pspec

a GParamSpec of the property.

 

excluded_props

a set of user-specified properties to exclude or NULL to show all changes.

[array zero-terminated=1][element-type gchar*][allow-none]

gst_object_default_error ()

void
gst_object_default_error (GstObject *source,
                          const GError *error,
                          const gchar *debug);

A default error function that uses g_printerr() to display the error message and the optional debug sting..

The default handler will simply print the error string using g_print.

Parameters

source

the GstObject that initiated the error.

 

error

the GError.

[in]

debug

an additional debug information string, or NULL.

[in][allow-none]

gst_object_check_uniqueness ()

gboolean
gst_object_check_uniqueness (GList *list,
                             const gchar *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 carefull when passing a list with a locked object.

Parameters

list

a list of GstObject to check through.

[transfer none][element-type Gst.Object]

name

the name to search for

 

Returns

TRUE if a GstObject named name does not appear in list , FALSE if it does.

MT safe. Grabs and releases the LOCK of each object in the list.


gst_object_has_ancestor ()

gboolean
gst_object_has_ancestor (GstObject *object,
                         GstObject *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.

Parameters

object

a GstObject to check

 

ancestor

a GstObject to check as ancestor

 

Returns

TRUE if ancestor is an ancestor of object .

MT safe. Grabs and releases object 's locks.


gst_object_ref ()

gpointer
gst_object_ref (gpointer object);

Increments the reference count on object . This function does not take the lock on object because it relies on atomic refcounting.

This object returns the input parameter to ease writing constructs like : result = gst_object_ref (object->parent);

Parameters

object

a GstObject to reference.

[type Gst.Object]

Returns

A pointer to object .

[transfer full][type Gst.Object]


gst_object_unref ()

void
gst_object_unref (gpointer object);

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.

The unref method should never be called with the LOCK held since this might deadlock the dispose function.

Parameters

object

a GstObject to unreference.

[type Gst.Object]

gst_object_ref_sink ()

gpointer
gst_object_ref_sink (gpointer object);

Increase the reference count of object , and possibly remove the floating reference, if object has a floating reference.

In other words, if the object is floating, then this call "assumes ownership" of the floating reference, converting it to a normal reference by clearing the floating flag while leaving the reference count unchanged. If the object is not floating, then this call adds a new normal reference increasing the reference count by one.

Parameters

object

a GstObject to sink

 

gst_object_replace ()

gboolean
gst_object_replace (GstObject **oldobj,
                    GstObject *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.

Either newobj and the value pointed to by oldobj may be NULL.

Parameters

oldobj

pointer to a place of a GstObject to replace.

[inout][transfer full]

newobj

a new GstObject.

[transfer none]

Returns

TRUE if newobj was different from oldobj


gst_object_get_path_string ()

gchar *
gst_object_get_path_string (GstObject *object);

Generates a string describing the path of object in the object hierarchy. Only useful (or used) for debugging.

Free-function: g_free

Parameters

object

a GstObject

 

Returns

a string describing the path of object . You must g_free() the string after usage.

MT safe. Grabs and releases the GstObject's LOCK for all objects in the hierarchy.

[transfer full]


gst_object_suggest_next_sync ()

GstClockTime
gst_object_suggest_next_sync (GstObject *object);

Returns a suggestion for timestamps where buffers should be split to get best controller results.

Parameters

object

the object that has controlled properties

 

Returns

Returns the suggested timestamp or GST_CLOCK_TIME_NONE if no control-rate was set.


gst_object_sync_values ()

gboolean
gst_object_sync_values (GstObject *object,
                        GstClockTime timestamp);

Sets the properties of the object, according to the GstControlSources that (maybe) handle them and for the given timestamp.

If this function fails, it is most likely the application developers fault. Most probably the control sources are not setup correctly.

Parameters

object

the object that has controlled properties

 

timestamp

the time that should be processed

 

Returns

TRUE if the controller values could be applied to the object properties, FALSE otherwise


gst_object_has_active_control_bindings ()

gboolean
gst_object_has_active_control_bindings
                               (GstObject *object);

Check if the object has an active controlled properties.

Parameters

object

the object that has controlled properties

 

Returns

TRUE if the object has active controlled properties


gst_object_set_control_bindings_disabled ()

void
gst_object_set_control_bindings_disabled
                               (GstObject *object,
                                gboolean 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.

Parameters

object

the object that has controlled properties

 

disabled

boolean that specifies whether to disable the controller or not.

 

gst_object_set_control_binding_disabled ()

void
gst_object_set_control_binding_disabled
                               (GstObject *object,
                                const gchar *property_name,
                                gboolean disabled);

This function is used to disable the GstController on a property for some time, i.e. gst_controller_sync_values() will do nothing for the property.

Parameters

object

the object that has controlled properties

 

property_name

property to disable

 

disabled

boolean that specifies whether to disable the controller or not.

 

gst_object_add_control_binding ()

gboolean
gst_object_add_control_binding (GstObject *object,
                                GstControlBinding *binding);

Attach the GstControlBinding to the object. If there already was a GstControlBinding for this property it will be replaced.

The object will take ownership of the binding .

Parameters

object

the controller object

 

binding

the GstControlBinding that should be used.

[transfer full]

Returns

FALSE if the given binding has not been setup for this object or has been setup for a non suitable property, TRUE otherwise.


gst_object_get_control_binding ()

GstControlBinding *
gst_object_get_control_binding (GstObject *object,
                                const gchar *property_name);

Gets the corresponding GstControlBinding for the property. This should be unreferenced again after use.

Parameters

object

the object

 

property_name

name of the property

 

Returns

the GstControlBinding for property_name or NULL if the property is not controlled.

[transfer full]


gst_object_remove_control_binding ()

gboolean
gst_object_remove_control_binding (GstObject *object,
                                   GstControlBinding *binding);

Removes the corresponding GstControlBinding. If it was the last ref of the binding, it will be disposed.

Parameters

object

the object

 

binding

the binding

 

Returns

TRUE if the binding could be removed.


gst_object_get_value ()

GValue *
gst_object_get_value (GstObject *object,
                      const gchar *property_name,
                      GstClockTime timestamp);

Gets the value for the given controlled property at the requested time.

Parameters

object

the object that has controlled properties

 

property_name

the name of the property to get

 

timestamp

the time the control-change should be read from

 

Returns

the GValue of the property at the given time, or NULL if the property isn't controlled.


gst_object_get_value_array ()

gboolean
gst_object_get_value_array (GstObject *object,
                            const gchar *property_name,
                            GstClockTime timestamp,
                            GstClockTime interval,
                            guint n_values,
                            gpointer 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.

This function is useful if one wants to e.g. draw a graph of the control curve or apply a control curve sample by sample.

The values are unboxed and ready to be used. The similar function gst_object_get_g_value_array() returns the array as GValues and is better suites for bindings.

Parameters

object

the object that has controlled properties

 

property_name

the name of the property to get

 

timestamp

the time that should be processed

 

interval

the time spacing between subsequent values

 

n_values

the number of values

 

values

array to put control-values in

 

Returns

TRUE if the given array could be filled, FALSE otherwise


gst_object_get_g_value_array ()

gboolean
gst_object_get_g_value_array (GstObject *object,
                              const gchar *property_name,
                              GstClockTime timestamp,
                              GstClockTime interval,
                              guint n_values,
                              GValue *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.

This function is useful if one wants to e.g. draw a graph of the control curve or apply a control curve sample by sample.

Parameters

object

the object that has controlled properties

 

property_name

the name of the property to get

 

timestamp

the time that should be processed

 

interval

the time spacing between subsequent values

 

n_values

the number of values

 

values

array to put control-values in

 

Returns

TRUE if the given array could be filled, FALSE otherwise


gst_object_get_control_rate ()

GstClockTime
gst_object_get_control_rate (GstObject *object);

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.

If the object is not under property control, this will return GST_CLOCK_TIME_NONE. This allows the element to avoid the sub-dividing.

The control-rate is not expected to change if the element is in GST_STATE_PAUSED or GST_STATE_PLAYING.

Parameters

object

the object that has controlled properties

 

Returns

the control rate in nanoseconds


gst_object_set_control_rate ()

void
gst_object_set_control_rate (GstObject *object,
                             GstClockTime control_rate);

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.

The control-rate should not change if the element is in GST_STATE_PAUSED or GST_STATE_PLAYING.

Parameters

object

the object that has controlled properties

 

control_rate

the new control-rate in nanoseconds.

 

Types and Values

struct GstObject

struct GstObject {
  GMutex         lock;        /* object LOCK */
  gchar         *name;        /* object name */
  GstObject     *parent;      /* this object's parent, weak ref */
  guint32        flags;
};

GStreamer base object class.

Members

GMutex lock;

object LOCK

 

gchar *name;

The name of the object

 

GstObject *parent;

this object's parent, weak ref

 

guint32 flags;

flags for this object

 

struct GstObjectClass

struct GstObjectClass {
  GInitiallyUnownedClass parent_class;

  const gchar *path_string_separator;

  /* signals */
  void          (*deep_notify)      (GstObject * object, GstObject * orig, GParamSpec * pspec);

  /* virtual methods for subclasses */
};

GStreamer base object class.

Members

GInitiallyUnownedClass parent_class;

parent

 

const gchar *path_string_separator;

separator used by gst_object_get_path_string()

 

deep_notify ()

default signal handler

 

enum GstObjectFlags

The standard flags that an gstobject may have.

Members

GST_OBJECT_FLAG_LAST

subclasses can add additional flags starting from this flag

 

Property Details

The “name” property

  “name”                     gchar *

The name of the object.

Flags: Read / Write / Construct

Default value: NULL


The “parent” property

  “parent”                   GstObject *

The parent of the object.

Flags: Read / Write

Signal Details

The “deep-notify” signal

void
user_function (GstObject  *gstobject,
               GstObject  *prop_object,
               GParamSpec *prop,
               gpointer    user_data)

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.

Parameters

gstobject

a GstObject

 

prop_object

the object that originated the signal

 

prop

the property that changed

 

user_data

user data set when the signal handler was connected.

 

Flags: No Hooks