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The controller subsystem 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 continously 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!
mark gobject-properties paramspecs that make sense to be controlled, by GST_PARAM_CONTROLLABLE.
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 its not a lot to change.
first put some properties under control, by calling controller = gst_object_control_properties (object, "prop1", "prop2",...);
create a GstControlSource.
csource = gst_interpolation_control_source_new()
;
gst_interpolation_control_source_set_interpolation_mode(csource, mode);
Attach the GstControlSource on the controller to a property. gst_controller_set_control_source (controller, "prop1", csource);
Set the control values gst_interpolation_control_source_set (csource,0 * GST_SECOND, value1); gst_interpolation_control_source_set (csource,1 * GST_SECOND, value2);
start your pipeline
gboolean gst_controller_init (int *argc
,char ***argv
);
Initializes the use of the controller library. Suggested to be called right
after gst_init()
.
GstController * gst_controller_new (GObject *object
,...
);
Creates a new GstController for the given object's properties
object |
the object of which some properties should be controlled |
|
... |
|
GstController * gst_controller_new_list (GObject *object
,GList *list
);
Creates a new GstController for the given object's properties
GstController * gst_controller_new_valist (GObject *object
,va_list var_args
);
Creates a new GstController for the given object's properties
object |
the object of which some properties should be controlled |
|
var_args |
|
gboolean gst_controller_remove_properties (GstController *self
,...
);
Removes the given object properties from the controller
self |
the controller object from which some properties should be removed |
|
... |
|
gboolean gst_controller_remove_properties_list (GstController *self
,GList *list
);
Removes the given object properties from the controller
self |
the controller object from which some properties should be removed |
|
list |
GList of property names that should be removed |
gboolean gst_controller_remove_properties_valist (GstController *self
,va_list var_args
);
Removes the given object properties from the controller
self |
the controller object from which some properties should be removed |
|
var_args |
|
void gst_controller_set_disabled (GstController *self
,gboolean disabled
);
This function is used to disable all properties of the GstController
for some time, i.e. gst_controller_sync_values()
will do nothing.
self |
the GstController which should be disabled |
|
disabled |
boolean that specifies whether to disable the controller or not. |
Since: 0.10.14
void gst_controller_set_property_disabled (GstController *self
,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.
self |
the GstController which should be disabled |
|
property_name |
property to disable |
|
disabled |
boolean that specifies whether to disable the controller or not. |
Since: 0.10.14
GstClockTime
gst_controller_suggest_next_sync (GstController *self
);
Returns a suggestion for timestamps where buffers should be split to get best controller results.
Since: 0.10.13
gboolean gst_controller_sync_values (GstController *self
,GstClockTime timestamp
);
Sets the properties of the element, according to the controller that (maybe) handles 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.
GstControlSource * gst_controller_get_control_source (GstController *self
,const gchar *property_name
);
Gets the corresponding GstControlSource for the property. This should be unreferenced again after use.
self |
the controller object |
|
property_name |
name of the property for which the GstControlSource should be get |
the GstControlSource for property_name
or NULL if the property is not
controlled by this controller or no GstControlSource was assigned yet.
Since: 0.10.14
gboolean gst_controller_set_control_source (GstController *self
,const gchar *property_name
,GstControlSource *csource
);
Sets the GstControlSource for property_name
. If there already was a GstControlSource
for this property it will be unreferenced.
self |
the controller object |
|
property_name |
name of the property for which the GstControlSource should be set |
|
csource |
the GstControlSource that should be used for the property |
FALSE
if the given property isn't handled by the controller or the new GstControlSource
couldn't be bound to the property, TRUE
if everything worked as expected.
Since: 0.10.14
GValue * gst_controller_get (GstController *self
,const gchar *property_name
,GstClockTime timestamp
);
Gets the value for the given controller-handled property at the requested time.
self |
the controller object which handles the properties |
|
property_name |
the name of the property to get |
|
timestamp |
the time the control-change should be read from |
the GValue of the property at the given time, or NULL
if the
property isn't handled by the controller
gboolean gst_controller_get_value_arrays (GstController *self
,GstClockTime timestamp
,GSList *value_arrays
);
Function to be able to get an array of values for one or more given element properties.
All fields of the GstValueArray
in the list must be filled correctly.
Especially the GstValueArray->values arrays must be big enough to keep
the requested amount of values.
The types of the values in the array are the same as the property's type.
This doesn't modify the controlled GObject properties!
gboolean gst_controller_get_value_array (GstController *self
,GstClockTime timestamp
,GstValueArray *value_array
);
Function to be able to get an array of values for one element property.
All fields of value_array
must be filled correctly. Especially the
value_array->values
array must be big enough to keep the requested amount
of values (as indicated by the nbsamples field).
The type of the values in the array is the same as the property's type.
This doesn't modify the controlled GObject property!
gboolean gst_controller_set (GstController *self
,const gchar *property_name
,GstClockTime timestamp
,GValue *value
);
gst_controller_set
is deprecated and should not be used in newly-written code.
Use GstControlSource, for example GstInterpolationControlSource directly.
Set the value of given controller-handled property at a certain time.
gboolean gst_controller_set_from_list (GstController *self
,const gchar *property_name
,GSList *timedvalues
);
gst_controller_set_from_list
is deprecated and should not be used in newly-written code.
Use GstControlSource, for example GstInterpolationControlSource directly.
Sets multiple timed values at once.
self |
the controller object which handles the properties |
|
property_name |
the name of the property to set |
|
timedvalues |
a list with GstTimedValue items |
gboolean gst_controller_unset (GstController *self
,const gchar *property_name
,GstClockTime timestamp
);
gst_controller_unset
is deprecated and should not be used in newly-written code.
Use GstControlSource, for example GstInterpolationControlSource directly.
Used to remove the value of given controller-handled property at a certain time.
gboolean gst_controller_unset_all (GstController *self
,const gchar *property_name
);
gst_controller_unset_all
is deprecated and should not be used in newly-written code.
Use GstControlSource, for example GstInterpolationControlSource directly.
Used to remove all time-stamped values of given controller-handled property
self |
the controller object which handles the properties |
|
property_name |
the name of the property to unset |
FALSE
if the values couldn't be unset (ex : properties not handled
by controller), TRUE
otherwise
Since: 0.10.5
const GList * gst_controller_get_all (GstController *self
,const gchar *property_name
);
gst_controller_get_all
is deprecated and should not be used in newly-written code.
Use GstControlSource, for example GstInterpolationControlSource directly.
Returns a read-only copy of the list of GstTimedValue for the given property. Free the list after done with it.
This doesn't modify the controlled GObject property!
gboolean gst_controller_set_interpolation_mode (GstController *self
,const gchar *property_name
,GstInterpolateMode mode
);
gst_controller_set_interpolation_mode
is deprecated and should not be used in newly-written code.
Use GstControlSource, for example GstInterpolationControlSource directly.
Sets the given interpolation mode on the given property.
User interpolation is not yet available and quadratic interpolation is deprecated and maps to cubic interpolation.