GstDeviceMonitor

GstDeviceMonitor — A device monitor and prober

Functions

Types and Values

Object Hierarchy


Includes

#include <gst/gst.h>

Description

A GstDeviceMonitor subclass is provided by a plugin that handles devices if there is a way to programatically list connected devices. It can also optionally provide updates to the list of connected devices.

Each GstDeviceMonitor subclass is a singleton, a plugin should normally provide a single subclass for all devices.

Applications would normally use a GstGlobalDeviceMonitor to monitor devices from all revelant monitors.

Functions

gst_device_monitor_can_monitor ()

gboolean
gst_device_monitor_can_monitor (GstDeviceMonitor *monitor);

If this function returns TRUE, then the device monitor can monitor if devices are added or removed. Otherwise, it can only do static probing.

Parameters

monitor

a GstDeviceMonitor

 

Returns

TRUE if the GstDeviceMonitor support monitoring, FALSE otherwise


gst_device_monitor_class_add_metadata ()

void
gst_device_monitor_class_add_metadata (GstDeviceMonitorClass *klass,
                                       const gchar *key,
                                       const gchar *value);

Set key with value as metadata in klass .

Parameters

klass

class to set metadata for

 

key

the key to set

 

value

the value to set

 

gst_device_monitor_class_add_static_metadata ()

void
gst_device_monitor_class_add_static_metadata
                               (GstDeviceMonitorClass *klass,
                                const gchar *key,
                                const gchar *value);

Set key with value as metadata in klass .

Same as gst_device_monitor_class_add_metadata(), but value must be a static string or an inlined string, as it will not be copied. (GStreamer plugins will be made resident once loaded, so this function can be used even from dynamically loaded plugins.)

Parameters

klass

class to set metadata for

 

key

the key to set

 

value

the value to set

 

Since 1.4


gst_device_monitor_class_get_metadata ()

const gchar *
gst_device_monitor_class_get_metadata (GstDeviceMonitorClass *klass,
                                       const gchar *key);

Get metadata with key in klass .

Parameters

klass

class to get metadata for

 

key

the key to get

 

Returns

the metadata for key .

Since 1.4


gst_device_monitor_class_set_metadata ()

void
gst_device_monitor_class_set_metadata (GstDeviceMonitorClass *klass,
                                       const gchar *longname,
                                       const gchar *classification,
                                       const gchar *description,
                                       const gchar *author);

Sets the detailed information for a GstDeviceMonitorClass.

This function is for use in _class_init functions only.

Parameters

klass

class to set metadata for

 

longname

The long English name of the device monitor. E.g. "File Sink"

 

classification

String describing the type of device monitor, as an unordered list separated with slashes ('/'). See draft-klass.txt of the design docs for more details and common types. E.g: "Sink/File"

 

description

Sentence describing the purpose of the device monitor. E.g: "Write stream to a file"

 

author

Name and contact details of the author(s). Use \n to separate multiple author metadata. E.g: "Joe Bloggs <joe.blogs at foo.com>"

 

Since 1.4


gst_device_monitor_class_set_static_metadata ()

void
gst_device_monitor_class_set_static_metadata
                               (GstDeviceMonitorClass *klass,
                                const gchar *longname,
                                const gchar *classification,
                                const gchar *description,
                                const gchar *author);

Sets the detailed information for a GstDeviceMonitorClass.

This function is for use in _class_init functions only.

Same as gst_device_monitor_class_set_metadata(), but longname , classification , description , and author must be static strings or inlined strings, as they will not be copied. (GStreamer plugins will be made resident once loaded, so this function can be used even from dynamically loaded plugins.)

Parameters

klass

class to set metadata for

 

longname

The long English name of the element. E.g. "File Sink"

 

classification

String describing the type of element, as an unordered list separated with slashes ('/'). See draft-klass.txt of the design docs for more details and common types. E.g: "Sink/File"

 

description

Sentence describing the purpose of the element. E.g: "Write stream to a file"

 

author

Name and contact details of the author(s). Use \n to separate multiple author metadata. E.g: "Joe Bloggs <joe.blogs at foo.com>"

 

Since 1.4


gst_device_monitor_device_add ()

void
gst_device_monitor_device_add (GstDeviceMonitor *monitor,
                               GstDevice *device);

Posts a message on the monitor's GstBus to inform applications that a new device has been added.

This is for use by subclasses.

Parameters

monitor

a GstDeviceMonitor

 

device

a GstDevice that has been added.

[transfer full]

Since 1.4


gst_device_monitor_device_remove ()

void
gst_device_monitor_device_remove (GstDeviceMonitor *monitor,
                                  GstDevice *device);

Posts a message on the monitor's GstBus to inform applications that a device has been removed.

This is for use by subclasses.

Parameters

monitor

a GstDeviceMonitor

 

device

a GstDevice that has been removed

 

Since 1.4


gst_device_monitor_get_bus ()

GstBus *
gst_device_monitor_get_bus (GstDeviceMonitor *monitor);

Gets the GstBus of this GstDeviceMonitor

Parameters

monitor

a GstDeviceMonitor

 

Returns

a GstBus.

[transfer full]

Since 1.4


gst_device_monitor_get_devices ()

GList *
gst_device_monitor_get_devices (GstDeviceMonitor *monitor);

Gets a list of devices that this monitor understands. This may actually probe the hardware if the monitor is not currently started.

Parameters

monitor

A GstDeviceMonitor

 

Returns

a GList of GstDevice.

[transfer full][element-type GstDevice]

Since 1.4


gst_device_monitor_get_factory ()

GstDeviceMonitorFactory *
gst_device_monitor_get_factory (GstDeviceMonitor *monitor);

Retrieves the factory that was used to create this device monitor.

Parameters

monitor

a GstDeviceMonitor to request the device monitor factory of.

 

Returns

the GstDeviceMonitorFactory used for creating this device monitor. no refcounting is needed.

[transfer none]

Since 1.4


gst_device_monitor_register ()

gboolean
gst_device_monitor_register (GstPlugin *plugin,
                             const gchar *name,
                             guint rank,
                             GType type);

Create a new device monitorfactory capable of instantiating objects of the type and add the factory to plugin .

Parameters

plugin

GstPlugin to register the device monitor with, or NULL for a static device monitor.

[allow-none]

name

name of device monitors of this type

 

rank

rank of device monitor (higher rank means more importance when autoplugging)

 

type

GType of device monitor to register

 

Returns

TRUE, if the registering succeeded, FALSE on error

Since 1.4


gst_device_monitor_start ()

gboolean
gst_device_monitor_start (GstDeviceMonitor *monitor);

Starts monitoring the devices. This will cause GST_MESSAGE_DEVICE messages to be posted on the monitor's bus when devices are added or removed from the system.

Since the GstDeviceMonitor is a singleton, gst_device_monitor_start() may already have been called by another user of the object, gst_device_monitor_stop() needs to be called the same number of times.

Parameters

monitor

A GstDeviceMonitor

 

Returns

TRUE if the device monitoring could be started

Since 1.4


gst_device_monitor_stop ()

void
gst_device_monitor_stop (GstDeviceMonitor *monitor);

Decreases the use-count by one. If the use count reaches zero, this GstDeviceMonitor will stop monitoring the devices. This needs to be called the same number of times that gst_device_monitor_start() was called.

Parameters

monitor

A GstDeviceMonitor

 

Since 1.4

Types and Values

struct GstDeviceMonitor

struct GstDeviceMonitor {
  GstObject         parent;

  /* Protected by the Object lock */
  GList *devices;
};

The structure of the base GstDeviceMonitor

Members

GstObject parent;

The parent GstObject

 

GList *devices;

a GList of the GstDevice objects

 

Since 1.4


struct GstDeviceMonitorClass

struct GstDeviceMonitorClass {
  GstObjectClass    parent_class;

  GstDeviceMonitorFactory     *factory;

  GList*      (*probe) (GstDeviceMonitor * monitor);

  gboolean    (*start) (GstDeviceMonitor * monitor);
  void        (*stop)  (GstDeviceMonitor * monitor);
};

The structure of the base GstDeviceMonitorClass

Members

GstObjectClass parent_class;

the parent GstObjectClass structure

 

GstDeviceMonitorFactory *factory;

a pointer to the GstDeviceMonitorFactory that creates this monitor

 

probe ()

Returns a list of devices that are currently available. This should never block.

 

start ()

Starts monitoring for new devices. Only subclasses that can know that devices have been added or remove need to implement this method.

 

stop ()

Stops monitoring for new devices. Only subclasses that implement the start() method need to implement this method.

 

Since 1.4

See Also

GstDevice, GstGlobalDeviceMonitor