Microsoft DirectX 8.1 (C++)

Sequence of Operations in the Tuning Process

The following steps assume that the platform is Windows® XP Home Edition or Windows XP Professional, and that the Guide Store repository has previously been populated with data:

  1. The application creates an instance of the Video Control and the Guide Store, and displays a list of programs based on data retrieved from the Guide Store.
  2. The end user selects a program and the application retrieves the tune request (described below) that is associated with the selected program.
  3. The application submits the tune request to the Video Control, which examines its network type. Note that the application does not need to examine the tune request at all; it simply passes it from the Guide Store to the Video Control.
  4. The Video Control constructs a filter graph that can play the tune request.
  5. If the graph is a BDA digital TV graph, the Video Control submits the tune request to the Network Provider, otherwise the Video Control simply builds a WDM analog TV graph and sets the channel.
  6. The Network Provider uses the Locator information associated with the tune request, or if none is present, the default Locator for the tuning space, to set the necessary frequency and modulation parameters on the tuner. The tuner passes the signal on to the BDA capture filter, which digitizes the signal and passes the MPEG-2 transport stream to the MPEG-2 Demultiplexer. The Network Provider, MPEG-2 Demultiplexer, and TIF work together automatically to route the correct audio, video and data streams based on the Components collection in the tune request, or the DefaultPreferredComponentTypes associated with the tuning space.
  7. As data begins flowing through the filter graph, the TIF begins to receive the transport stream tables containing Packet Identifier (PID) values for stream components including EPG information. It populates the Components collection in the tune request with the actual components available on the specified service, and sends events to the Network Provider and Guide Store loader when a complete set of EPG information has been obtained or any information changes.
  8. The loader retrieves the EPG information from the TIF and uses it to create new tune requests, which it stores in the Guide Store repository.
  9. The application updates its program listing periodically and deletes old entries from the Guide Store.