GstController

GstController — dynamic parameter control subsystem

Synopsis


#include <gst/controller/gstcontroller.h>


            GstController;
enum        GstInterpolateMode;
gboolean    gst_controller_init             (int *argc,
                                             char ***argv);
GstController* gst_controller_new           (GObject *object,
                                             ...);
GstController* gst_controller_new_list      (GObject *object,
                                             GList *list);
GstController* gst_controller_new_valist    (GObject *object,
                                             va_list var_args);
gboolean    gst_controller_remove_properties
                                            (GstController *self,
                                             ...);
gboolean    gst_controller_remove_properties_list
                                            (GstController *self,
                                             GList *list);
gboolean    gst_controller_remove_properties_valist
                                            (GstController *self,
                                             va_list var_args);
gboolean    gst_controller_set              (GstController *self,
                                             gchar *property_name,
                                             GstClockTime timestamp,
                                             GValue *value);
gboolean    gst_controller_set_from_list    (GstController *self,
                                             gchar *property_name,
                                             GSList *timedvalues);
gboolean    gst_controller_unset            (GstController *self,
                                             gchar *property_name,
                                             GstClockTime timestamp);
gboolean    gst_controller_unset_all        (GstController *self,
                                             gchar *property_name);
GValue*     gst_controller_get              (GstController *self,
                                             gchar *property_name,
                                             GstClockTime timestamp);
const GList* gst_controller_get_all         (GstController *self,
                                             gchar *property_name);
gboolean    gst_controller_sync_values      (GstController *self,
                                             GstClockTime timestamp);
gboolean    gst_controller_get_value_arrays (GstController *self,
                                             GstClockTime timestamp,
                                             GSList *value_arrays);
gboolean    gst_controller_get_value_array  (GstController *self,
                                             GstClockTime timestamp,
                                             GstValueArray *value_array);
gboolean    gst_controller_set_interpolation_mode
                                            (GstController *self,
                                             gchar *property_name,
                                             GstInterpolateMode mode);
#define     GST_PARAM_CONTROLLABLE

Object Hierarchy


  GObject
   +----GstController

Description

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 = g_object_control_properties(object, "prop1", "prop2",...);
set how the controller will smooth inbetween values. gst_controller_set_interpolation_mode(controller,"prop1",mode);
set key values gst_controller_set (controller, "prop1" ,0 * GST_SECOND, value1); gst_controller_set (controller, "prop1" ,1 * GST_SECOND, value2);
start your pipeline

Details

GstController

typedef struct _GstController GstController;

The instance structure of GstController

enum GstInterpolateMode

typedef enum
{
  GST_INTERPOLATE_NONE,
  GST_INTERPOLATE_TRIGGER,
  GST_INTERPOLATE_LINEAR,
  GST_INTERPOLATE_QUADRATIC,
  GST_INTERPOLATE_CUBIC,
  GST_INTERPOLATE_USER
} GstInterpolateMode;

The various interpolation modes available.

`GST_INTERPOLATE_NONE`	steps-like interpolation, default
`GST_INTERPOLATE_TRIGGER`	returns the default value of the property, except for times with specific values
`GST_INTERPOLATE_LINEAR`	linear interpolation
`GST_INTERPOLATE_QUADRATIC`	square interpolation
`GST_INTERPOLATE_CUBIC`	cubic interpolation
`GST_INTERPOLATE_USER`	user-provided interpolation

gst_controller_init ()

gboolean    gst_controller_init             (int *argc,
                                             char ***argv);

Initializes the use of the controller library. Suggested to be called right after gst_init().

`argc` :	pointer to the commandline argument count
`argv` :	pointer to the commandline argument values
Returns :	the `TRUE` for success.

gst_controller_new ()

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
`...` :	`NULL` terminated list of property names that should be controlled
Returns :	the new controller.

Since 0.9

gst_controller_new_list ()

GstController* gst_controller_new_list      (GObject *object,
                                             GList *list);

Creates a new GstController for the given object's properties

`object` :	the object of which some properties should be controlled
`list` :	list of property names that should be controlled
Returns :	the new controller.

Since 0.9

gst_controller_new_valist ()

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` :	`NULL` terminated list of property names that should be controlled
Returns :	the new controller.

Since 0.9

gst_controller_remove_properties ()

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
`...` :	`NULL` terminated list of property names that should be removed
Returns :	`FALSE` if one of the given property isn't handled by the controller, `TRUE` otherwise

Since 0.9

gst_controller_remove_properties_list ()

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
Returns :	`FALSE` if one of the given property isn't handled by the controller, `TRUE` otherwise

Since 0.9

gst_controller_remove_properties_valist ()

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` :	`NULL` terminated list of property names that should be removed
Returns :	`FALSE` if one of the given property isn't handled by the controller, `TRUE` otherwise

Since 0.9

gst_controller_set ()

gboolean    gst_controller_set              (GstController *self,
                                             gchar *property_name,
                                             GstClockTime timestamp,
                                             GValue *value);

Set the value of given controller-handled property at a certain time.

`self` :	the controller object which handles the properties
`property_name` :	the name of the property to set
`timestamp` :	the time the control-change is schedules for
`value` :	the control-value
Returns :	FALSE if the values couldn't be set (ex : properties not handled by controller), TRUE otherwise

Since 0.9

gst_controller_set_from_list ()

gboolean    gst_controller_set_from_list    (GstController *self,
                                             gchar *property_name,
                                             GSList *timedvalues);

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
Returns :	`FALSE` if the values couldn't be set (ex : properties not handled by controller), `TRUE` otherwise

Since 0.9

gst_controller_unset ()

gboolean    gst_controller_unset            (GstController *self,
                                             gchar *property_name,
                                             GstClockTime timestamp);

Used to remove the value of given controller-handled property at a certain time.

`self` :	the controller object which handles the properties
`property_name` :	the name of the property to unset
`timestamp` :	the time the control-change should be removed from
Returns :	`FALSE` if the values couldn't be unset (ex : properties not handled by controller), `TRUE` otherwise

Since 0.9

gst_controller_unset_all ()

gboolean    gst_controller_unset_all        (GstController *self,
                                             gchar *property_name);

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
Returns :	`FALSE` if the values couldn't be unset (ex : properties not handled by controller), `TRUE` otherwise

Since 0.10.5

gst_controller_get ()

GValue*     gst_controller_get              (GstController *self,
                                             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
Returns :	the GValue of the property at the given time, or `NULL` if the property isn't handled by the controller

Since 0.9

gst_controller_get_all ()

const GList* gst_controller_get_all         (GstController *self,
                                             gchar *property_name);

Returns a read-only copy of the list of GstTimedValue for the given property. Free the list after done with it.

`self` :	the controller to get the list from
`property_name` :	the name of the property to get the list for
Returns :	a copy of the list, or `NULL` if the property isn't handled by the controller

Since 0.9

gst_controller_sync_values ()

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.

`self` :	the controller that handles the values
`timestamp` :	the time that should be processed
Returns :	`TRUE` if the controller values could be applied to the object properties, `FALSE` otherwise

Since 0.9

gst_controller_get_value_arrays ()

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.

If the GstValueArray->values array in list nodes is NULL, it will be created by the function. The type of the values in the array are the same as the property's type.

`self` :	the controller that handles the values
`timestamp` :	the time that should be processed
`value_arrays` :	list to return the control-values in
Returns :	`TRUE` if the given array(s) could be filled, `FALSE` otherwise

Since 0.9

gst_controller_get_value_array ()

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 properties

If the GstValueArray->values array is NULL, it will be created by the function. The type of the values in the array are the same as the property's type.

`self` :	the controller that handles the values
`timestamp` :	the time that should be processed
`value_array` :	array to put control-values in
Returns :	`TRUE` if the given array(s) could be filled, `FALSE` otherwise

Since 0.9

gst_controller_set_interpolation_mode ()

gboolean    gst_controller_set_interpolation_mode
                                            (GstController *self,
                                             gchar *property_name,
                                             GstInterpolateMode mode);

Sets the given interpolation mode on the given property.

`self` :	the controller object
`property_name` :	the name of the property for which to change the interpolation
`mode` :	interpolation mode
Returns :	`TRUE` if the property is handled by the controller, `FALSE` otherwise

Since 0.9

GST_PARAM_CONTROLLABLE

#define	GST_PARAM_CONTROLLABLE	(1 << (G_PARAM_USER_SHIFT + 1))

Use this flag on GstElement properties you wish to be (eventually) handled by a GstController. TODO: needs to go to gstelemnt.h (to avoid clashes on G_PARAM_USER_SHIFT)