The Influence Of Second Encoding On Digital Television Picture Quality

This paper aims to study the problem of poor video frequency of digital television complained by the viewers of SITV. It seems that digital television in Shanghai does have poorer video frequency compared to cable TV. By testing each step of digital television system in its process of operation and making objective data analysis, the paper finally shows that the existing second encoding, which is using the frequency of 4.2Mb/s in display system of SITV, leads to a poorer video frequency.Meanwhile, by adjusting parameters of key equipment in the system,combining parameters between key equipment,upgrading key equipment, testing and analyzing after-adjustment data, the paper also demonstrates how to simply improve video frequency of Shanghai interactive digital television without changing system structure and increasing operating costs.The TV development has entered into an important stage, upgrading from Analogy System to Digital System. The Cable Front-end digital Renovation project has begun in Shanghai. Under the trend of promoting Digital TV, this paper found out the main cause of poor video frequency of SITV and put forward that the most effective way to resolve the problem of poor quality of video frequency of digital television is to upgrade present encoding width from 4.2Mb/s to 6Mb/s on the basis of large amount of objective data analysis. This method has been adopted by Shanghai Cable Network Company, and 6Mb/s encoding width will be utilized in the renovation of new Shanghai Cable Network. At the same time, the large amount of testing data for the Digital System in this paper can be regarded as the useful reference for my colleagues who are engaged in building Digital TV System and selecting Digital Audio Equipment.