GstControlSource

GstControlSource — base class for control source sources

Synopsis

#include <libs/controller/gstcontrolsource.h>

struct              GstControlSource;
struct              GstControlSourceClass;
gboolean            (*GstControlSourceBind)             (GstControlSource *self,
                                                         GParamSpec *pspec);
gboolean            (*GstControlSourceGetValue)         (GstControlSource *self,
                                                         GstClockTime timestamp,
                                                         GValue *value);
gboolean            (*GstControlSourceGetValueArray)    (GstControlSource *self,
                                                         GstClockTime timestamp,
                                                         GstValueArray *value_array);
struct              GstTimedValue;
struct              GstValueArray;
gboolean            gst_control_source_bind             (GstControlSource *self,
                                                         GParamSpec *pspec);
gboolean            gst_control_source_get_value        (GstControlSource *self,
                                                         GstClockTime timestamp,
                                                         GValue *value);
gboolean            gst_control_source_get_value_array  (GstControlSource *self,
                                                         GstClockTime timestamp,
                                                         GstValueArray *value_array);

Object Hierarchy

  GObject
   +----GstControlSource
         +----GstInterpolationControlSource
         +----GstLFOControlSource

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

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

The class structure of GstControlSource.

GObjectClass parent_class;

 Parent class

GstControlSourceBind bind;

 Class method for binding the GstControlSource to a specific GParamSpec

GstControlSourceBind ()

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

Function for binding a GstControlSource to a GParamSpec.

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.

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.

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.

struct GstTimedValue

struct GstTimedValue {
  GstClockTime timestamp;
  GValue value;
};

Structure for saving a timestamp and a value.

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.

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

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.

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.

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.

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
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