Design And Realization Of An IP-phone Codec Based On G.729

Based on the analysis to the present IP phone technologies,the idea of in-corporation IP phone is presented in this paper,and the IP phone encoder and codec meeting ITU-T G.729 protocolis investigated. The IP phone codec carry out the tasks of collecting and playing-back of speech signal,and asynchronous communication with PC's serial port ,etc.The hardware of the IP phone to be designed is based on the high speed digital signal processor (TI'S TMS320VC5409),while the compression and decompression core in the software is based on the ITU-T G.729,resulting a favorable speech quality at the data rate of SKbps,with the compression ratio of 16 to 1 .In this thesis,the concept and characteristics of the IP phone codec are analyzed firstly. Then the ITU-T G.729 protocol is discussed in detail,along with C code simulation and DSP realization. The optimization of G.729 codec mainly includes the following three aspects:utilization of multifunction instructions,appropriate use of registers,management of memory,and in particular,the prevention of pipeline contention. Secondly,the hardware design is described,including system requirement analysis,overall function diagram,chip selection,and so on. In the description of circuit design,the emphasis is paid the following hardware modules:AD/DA inverter,DSP module,external program/data memory,CPLD control logic,serial communication module,power module,and so on. Problems and the corresponding solutions found in the design and debug stage are discussed,too. Finally,the low-level software driver design is presented in detail,including system booting,initialization of DSP registers,CPLD logic and timing control,drivers for asynchronous communication FIFO,and drivers for AD converter.