The Design And Implementation Of Common Data Download Module Based On DTV Software

Digital television, also known as digital TV or digital TV, It refers to the collection from the program, program production to transmission links are used to digitally processing an end-to-end system. It is not only the same as traditional TV broadcast-style broadcast programs, interactive way to broadcast programs. Digital TV typically is based on the MPEG standard to compress video and audio signals, and digitally transfer.The project of DTV software Y2is a DTV’s software developed for the Japanese market system. It is developed based on the Japanese digital TV standard ISDB. ISDB standard is extended on the basis of the MPEG standard. The DTV software project is divided into three layers, namely:the system layer, middle layer, application layer. This paper studies a subsystem of the application layer-Common Data Download module, which abbreviated as CDD.First, the article elaborated on the Common Data Download module related to the Japanese digital TV standard ISDB agreement form as well as some basic knowledge. Next, the article illustrates several important tables to enumerate the characterization significance of the role of each field in each table as well as specific values.The datas which to be download includes PNG files, so the article also examined the compression algorithm of PNG image. PNG files use one kind of lossless compression algorithm which derived from the compression rate LZ77and Huffman. Its features includes:support the transmission of network color image, support for the Alpha channel, define the transparent area and multiple transparent, and gradually refine the display picture. The images of PNG have characteristics of high-fidelity, transparency and the file size smaller, so it would be widely used.The paper designs and implements a common data download module. The article takes a step-by-step approach to analysis the needs of the Common Data Download module. And it shows an overall architecture. Then, the article introduces the functions and processes of the various sub-modules of common data download module. CDD_App are interface with the outside, whiche is mainly responsible for passing receive messages; CDD_ScheduleManager mainly responsible for receiving the download reservation information; CDD_DownloadManager is mainly responsible for the download of the actual data; CDD_DLContainer mainly responsible for the preservation download the booking information.