Research And Implementation Of Embedded Audio System

Audio system is applied in field of embedded system widely, and the requirement for it varies extremely. For communication products,the needs in performance is more strict than any other products. In network video telephone terminal, audio system's realization is based on Analog Device incorporation's dual core processor ADSP-BF561 and open sourced uClinux operation system. The audio system is developed with ADI's debug tool in Visual DSP++ integrated developing environment, which is designed for Blackfin series processors.In network video telephone terminal, audio system needs to perform 5 functions, i.e. voice gathering, encoding, decoding, exporting and network transmission. In order to make full use of the dual core's characteristic of ADSP-BF561, and reach better performance, the dual cores run parallelly, and every module are set to run in either blackfin core. At the same time, realize the audio system's all modules, including voice gathering, audio decoding, audio encoding and audio driver in uClinux-UDA1380 equipment driver.In the course of audio system's realization, some questions such as delay, dither, echo and package dropping could appear in audio's sending. So many procedures have been used to make the system or design as effective or functional as possible. The audio encoder's selection in handshake of calling, mostly base on the selecting measure to receive the most perfect encoder. Setting the circular buffer in encoding and decoding, valid buffer for voice data, resolving the questions of delay and dither in audio's transferring. Echo counteracting policy's realization solves the problem of echo in talking. And adding the time stamp realizes the audio and video data stream's synchronization. All the measures let the network video telephone terminal reach better performance.