Microsoft DirectX 8.1 (C++)

Microsoft Unified Tuning Model Objects (Visual Basic)

These objects are used primarily by (1) the Guide Store Loader to create tune requests for storage in the Guide Store, and (2) applications that install custom tuning spaces on a system. You can use Visual Basic® to write a loader that obtains EPG information from a source such as a Web page or network server, but loaders that obtain in-band EPG information from the BDA MPEG-2 Transport Information Filter must be written in C++. Visual Basic applications use these objects in the following scenarios to:

Create or modify a tune request dynamically.
Test the validity of a tuning space.
Create a default preferred components list that indicates user preferences for options such as the audio stream language.
Examine the components (such as audio substreams) available on a specified service.

For more information, see The Microsoft Unified Tuning Model.

Tuning Space Objects

Object	Description
AnalogRadioTuningSpace	Tuning space specific to terrestrial Radio networks. (Not implemented in this version of Microsoft® Windows® XP.)
AnalogTVTuningSpace	Represents a tuning space specific to analog TV networks.
ATSCTuningSpace	Represents a tuning space specific to ATSC networks.
DVBSTuningSpace	Represents a tuning space for satellite DVB (DVBS) networks.
DVBTuningSpace	Represents a tuning space specific to DVB networks.
SystemTuningSpaces	Provides access to all tuning spaces installed on the host system.

Tune Request Objects

Tune requests are created through a call to CreateTuneRequest. Applications generally will not create their own tune requests, but will obtain them from the Guide Store. Applications in some circumstances will use the tune request to obtain access to the Locator or tuning space objects.

Object	Description
IChannelTuneRequest	Implemented on tune request objects specific to analog TV networks.
IATSCChannelTuneRequest	Implemented on tune request objects specific to ATSC TV networks.
IDVBTuneRequest	Implemented on tune request objects specific to DVB TV networks.

Stream Component Objects

A "component" in this context refers to a sub-stream within a broadcast. Applications use these objects to examine the available components in a program stream once reception has begun, and to activate or inactivate each component. For example, an application may switch from an English audio stream to a German audio stream.

Object	Description
IComponent	Base class for specific component objects.
ComponentType	Base class for specific component type objects.
ComponentTypes	Provides a standard COM enumeration of component types.
IComponents	Provides a standard COM enumeration of components.
LanguageComponentType	Component type associated with the language of the sub-stream.
MPEG2ComponentType	Implemented on a component type associated with an MPEG-2 stream type.
ATSCComponentType	Implemented on a component type that indicates whether the audio sub-stream is in AC-3 format.

Locator Objects

Locator objects are used in some cases by the Network Provider and other filters in the graph to locate a service and all its available components (substreams) within a specified network. Each tuning space should have a default locator that was installed with the tuning space. The Guide Store loader can also specify a locator when it creates a tune request. Applications generally should have no need to use these objects.

Object	Description
ILocator	Base class for all derived locators. Not used directly by applications.
ATSCLocator	Contains locator information about tuning in an ATSC network.
DVBTLocator	Contains locator information about tuning in a DVB-T network.
DVBSLocator	Contains locator information about tuning in a DVB-S network.