The Speech-processing Card Develop Of Embedded VDR System

Ship borne voyage data recorder is equipment that records navigational information in a safe and restorable way, and all the information is recorded in real time and is irreversible. Speech signal is a type of the information, but there is no standard interface for it. The VDR was developed based on the embedded system. The speech-processing card is a subsystem of VDR, specific for the speech signal, and it provides a solution for multi channels speech processing.At first, from the discrete digital model of speech generate, this paper introduces the short-time analytic technology of speech signal, presents the classification of the speech compressing coder and the development of the speech compressing technology. Then it describes the main theory and some basic terms of G.723.1, the selected recommendation in low rate speech processing. After that, it presents the development and application of DSP. According to compare with GPP and MCU, DSP is selected to develop the speech card.Based on the function requirements, the speech card is designed in two ways. For hardware, the framework of speech card based on AC48304C-C chip is designed, and the circuit diagram is given in the paper. For software, with the 00 modularization techniques, the functions of the speech card are implemented. Its OS is VxWorks operating system, the development environment is Tornado, and the programming language is C++ language. This paper also introduces the design of the ECM and playback parts. At last this paper makes a summary, and introduces the problems in the development and our solutions for them.