Label: EPG SI data
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The implementation of the EPG system mainly includes the following key technologies: organization and generation of SI data at the originating end, reception and parsing of SI data at the receiving end, establishment of a SI database at the receiving end, display of an EPG interface, and the like. Some of them are implemented in hardware, such as the receiving and parsing of SI data; others are implemented in software, such as the establishment of the SI database and the display of the EPG interface. details as follows:
1. Organization and generation of SI data
The organization and generation of the originating SI data is performed by the originating SI server (SI Server). The SI analysis at the receiving end is opposite to this function, and is mainly responsible for the reconstruction of the SI data table. The organization of SI data is to conform to the grammar definition in DVB-SI and the grammar definition of MPEG-2, while looking at all the business information in the transmission network. The information content should correspond to the information in the PSI and SI tables. It can be described in the hierarchical order of Network-Transport Stream-Service-Event, and the hierarchical order of Transport Stream-Program(Service)-Element Stream is embedded.
2, the establishment of the SI database
SI data must be stored according to a certain data structure, so that it can be retrieved and extracted easily and quickly. Especially for the EPG system, the real-time operating system running in the set-top box needs to perform real-time actions on the user interaction. The quality of the SI database has an important impact on its performance. The SI data mainly includes: network information, transport stream information, service (program) information, business event information, etc., and a large amount of information is transmitted through descriptors, so a tree-like linked list can be used to store data, which constitutes a network, The tree structure of transport streams, services, and events, and descriptors that convey different information are represented by descriptor subclasses that inherit from the same base class.
3. Display technology of EPG system
When the TV program and the EPG application are started at the same time, the user may see the superposition of the program picture and the EPG interface. The TV picture seen by the user can be divided into three layers from front to back, followed by the graphics layer, the video layer and the background layer. .
The graphics layer here is also the OSD (On Screen Display) layer described below. The OSD interface display technology refers to superimposing text display on the image screen, so that the screen provides more additional information for the user. The video layer is the program currently being viewed (the decoded moving image); the background layer is the screen image when the TV program is not played and the EPG menu is activated. The EPG screen is built on the graphics layer, and the EPG screen is superimposed by a number of EPG graphics elements (such as buttons, text boxes, selection buttons, component containers, etc.). The state transition of the interface is implemented by a message-driven mechanism for message processing in the message response function. The screen image seen is the image of the three layers after the blend.
The general idea of ​​the EPG interface display is that SI data is separated from graphical elements. It includes the following parts: the retrieval and extraction of SI data, the graphic element library required by the EPG interface, the state transition controller, the OSD layer rendering engine, the OSD layer diagram, the video layer, the background layer and the three layers of Blend operations. The SI data retrieval module quickly retrieves the local SI database and provides the data information required for the current input focus of the EPG interface; the OSD layer graphic element library provides the graphic elements required for the interface, which is stored in the ROM of the local set top box; the state transfer controller receives The input of the user's remote controller provides the active focus required for the current display, and controls the flow of the state transition; the OSD layer image refers to the image synthesized by the EPG interface graphic elements; the OSD rendering engine determines the corresponding algorithm displayed, and receives the data provided by each module. , complete the drawing of the OSD layer graphics, and finally the blend operation of the OSD layer, the video layer and the background layer.
The advantages of digital TV are not only to provide high-quality video, audio programs, but more importantly, to provide business flexibility and diversity after digital processing. The electronic program guide, which describes the broadcast time and brief content of the program, helps the viewer to quickly and easily find the program of interest. It will be of great help to viewers watching TV, therefore. Attention must be paid to the research and content production of electronic television guide systems for digital television.
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