GstControlSource: GStreamer 0.10 Library Reference Manual

GstControlSource

GstControlSource — base class for control source sources

Functions

gboolean	(*GstControlSourceBind) ()
gboolean	(*GstControlSourceGetValue) ()
gboolean	(*GstControlSourceGetValueArray) ()
gboolean	gst_control_source_bind ()
gboolean	gst_control_source_get_value ()
gboolean	gst_control_source_get_value_array ()

Types and Values

struct	GstControlSource
struct	GstControlSourceClass
struct	GstTimedValue
struct	GstValueArray

Object Hierarchy

    GObject
    ╰── GstControlSource
        ├── GstInterpolationControlSource
        ╰── GstLFOControlSource

Includes

#include <libs/controller/gstcontrolsource.h>

Description

The GstControlSource is a base class for control value sources that could be used by GstController to get timestamp-value pairs.

A GstControlSource is used by first getting an instance, binding it to a GParamSpec (for example by using gst_controller_set_control_source()) and then by having it used by the GstController or calling gst_control_source_get_value() or gst_control_source_get_value_array().

For implementing a new GstControlSource one has to implement a GstControlSourceBind method, which will depending on the GParamSpec set up the control source for use and sets the GstControlSourceGetValue and GstControlSourceGetValueArray functions. These are then used by gst_control_source_get_value() or gst_control_source_get_value_array() to get values for specific timestamps.

Functions

GstControlSourceBind ()

gboolean
(*GstControlSourceBind) (GstControlSource *self,
                         GParamSpec *pspec);

Function for binding a GstControlSource to a GParamSpec.

Parameters

self	the GstControlSource instance
pspec	GParamSpec that should be bound to

Returns

TRUE if the property could be bound to the GstControlSource, FALSE otherwise.

GstControlSourceGetValue ()

gboolean
(*GstControlSourceGetValue) (GstControlSource *self,
                             GstClockTime timestamp,
                             GValue *value);

Function for returning a value for a given timestamp.

Parameters

self	the GstControlSource instance
timestamp	timestamp for which a value should be calculated
value	a GValue which will be set to the result. It must be initialized to the correct type.

Returns

TRUE if the value was successfully calculated.

GstControlSourceGetValueArray ()

gboolean
(*GstControlSourceGetValueArray) (GstControlSource *self,
                                  GstClockTime timestamp,
                                  GstValueArray *value_array);

Function for returning a GstValueArray for a given timestamp.

Parameters

self	the GstControlSource instance
timestamp	timestamp for which a value should be calculated
value_array	array to put control-values in

Returns

TRUE if the values were successfully calculated.

gst_control_source_bind ()

gboolean
gst_control_source_bind (GstControlSource *self,
                         GParamSpec *pspec);

Binds a GstControlSource to a specific property. This must be called only once for a GstControlSource.

Parameters

self	the GstControlSource object
pspec	GParamSpec for the property for which this GstControlSource should generate values.

Returns

TRUE if the GstControlSource was bound correctly, FALSE otherwise.

gst_control_source_get_value ()

gboolean
gst_control_source_get_value (GstControlSource *self,
                              GstClockTime timestamp,
                              GValue *value);

Gets the value for this GstControlSource at a given timestamp.

Parameters

self	the GstControlSource object
timestamp	the time for which the value should be returned
value	the value

Returns

FALSE if the value couldn't be returned, TRUE otherwise.

gst_control_source_get_value_array ()

gboolean
gst_control_source_get_value_array (GstControlSource *self,
                                    GstClockTime timestamp,
                                    GstValueArray *value_array);

Gets 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.

The type of the values in the array is the same as the property's type.

Parameters

self	the GstControlSource object
timestamp	the time that should be processed
value_array	array to put control-values in

Returns

TRUE if the given array could be filled, FALSE otherwise

Types and Values

struct GstControlSource

struct GstControlSource {
  GstControlSourceGetValue get_value;             /* Returns the value for a property at a given timestamp */
  GstControlSourceGetValueArray get_value_array;  /* Returns values for a property in a given timespan */
};

The instance structure of GstControlSource.

Members

GstControlSourceGetValue `get_value`;	Function for returning a value for a given timestamp
GstControlSourceGetValueArray `get_value_array`;	Function for returning a GstValueArray for a given timestamp

struct GstControlSourceClass

struct GstControlSourceClass {
  GObjectClass parent_class;
  
  GstControlSourceBind bind;  /* Binds the GstControlSource to a specific GParamSpec */
};

The class structure of GstControlSource.

Members

GObjectClass `parent_class`;	Parent class
GstControlSourceBind `bind`;	Class method for binding the GstControlSource to a specific GParamSpec

struct GstTimedValue

struct GstTimedValue {
  GstClockTime timestamp;
  GValue value;
};

Structure for saving a timestamp and a value.

Members

GstClockTime `timestamp`;	timestamp of the value change
GValue `value`;	the corresponding value

struct GstValueArray

struct GstValueArray {
  const gchar *property_name;
  gint nbsamples;
  GstClockTime sample_interval;
  gpointer *values;
};

Structure to receive multiple values at once.

Members

const gchar *`property_name`;	the name of the property this array belongs to
gint `nbsamples`;	number of samples requested
GstClockTime `sample_interval`;	interval between each sample
gpointer *`values`;	pointer to the array