GstControlSource

GstControlSource — base class for control source sources

Synopsis

#include <gst/gst.h>

                    GstValueArray;
struct              GstControlSource;
struct              GstControlSourceClass;
gboolean            (*GstControlSourceGetValue)         (GstControlSource *self,
                                                         GstClockTime timestamp,
                                                         gdouble *value);
gboolean            (*GstControlSourceGetValueArray)    (GstControlSource *self,
                                                         GstClockTime timestamp,
                                                         GstClockTime interval,
                                                         guint n_values,
                                                         gdouble *values);
struct              GstTimedValue;
gboolean            gst_control_source_get_value        (GstControlSource *self,
                                                         GstClockTime timestamp,
                                                         gdouble *value);
gboolean            gst_control_source_get_value_array  (GstControlSource *self,
                                                         GstClockTime timestamp,
                                                         GstClockTime interval,
                                                         guint n_values,
                                                         gdouble *values);

Object Hierarchy

  GObject
   +----GInitiallyUnowned
         +----GstObject
               +----GstControlSource

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.

Details

GstValueArray

typedef struct _GstValueArray GstValueArray;

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.

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 {
  GstObjectClass parent_class;
};

The class structure of GstControlSource.

GstObjectClass parent_class;

Parent class

GstControlSourceGetValue ()

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

Function for returning a value for a given timestamp.

`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,
                                                         GstClockTime interval,
                                                         guint n_values,
                                                         gdouble *values);

Function for returning an array of values for starting at a given timestamp.

`self` :	the GstControlSource instance
`timestamp` :	timestamp for which a value should be calculated
`interval` :	the time spacing between subsequent values
`n_values` :	the number of values
`values` :	array to put control-values in
Returns :	`TRUE` if the values were successfully calculated.

struct GstTimedValue

struct GstTimedValue {
  GstClockTime timestamp;
  gdouble      value;
};

Structure for saving a timestamp and a value.

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

gst_control_source_get_value ()

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

Gets the value for this GstControlSource at a given timestamp.

`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,
                                                         GstClockTime interval,
                                                         guint n_values,
                                                         gdouble *values);

Gets an array of values for for this GstControlSource.

`self` :	the GstControlSource object
`timestamp` :	the first timestamp
`interval` :	the time steps
`n_values` :	the number of values to fetch
`value_array` :	array to put control-values in
Returns :	`TRUE` if the given array could be filled, `FALSE` otherwise

			GStreamer 1.0 Core Reference Manual
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