Design And Application Research On Embedded Voice Record And Playback System Based On SPEEX

Embedded system has been developed rapidly since born, and voice application iscommon in the embedded system, and it is a trend that voice compression is used in theembedded system, by reason of limited storage space.Speex is a free voice codec software, and it is developed based on CELP algorithm.Because of its high quality encoding, low bitrate, variable bitrate, echo cancellationm, voicesub-transmission,etc, so it is highly suitable for being used as an embedded system audiocodec algorithm.The previous designs mostly transplanted Speex to voice process in the PC,such as voice transmission on internet,in order to decrease the transmission bandwith. Thispaper applies Speex to embedded system successfully, and makes full use of its voicecompression ability to resolve a problem that recorded voice occupies much space.This paper analyzes Speex’s encoding principle detailedly, and proves that Speex ishighly suitable for being used as embedded system audio codec algorithm through simulationanalysis. It is mainly divided to4core parts: voice sample, voice playback, voice data storageand USB communication. This system uses STM32F103, made by ST corporation, as themain controller.The voice sample module and voice playback module make full use ofSpeex’s powerful function in voice codec. They use the AD and PWM functional modulesintegrated in STM32F103, and make the voice data maximum storage and most originalregeneration. It utilizes two160bytes buffer.The encode process uses one buffer to store thesample quantity,and uses another buffer to encode the sampled quantity.The decode processuses one buffer to decode,and uses another buffer to playback the voice. Voice data storagemodule stores the encoded voice data by enlarging a Flash memory: M25P16.It communicateswith STM32F103through high speed SPI bus. USB communication module makes thisembedded system communicate with PC, which enables M25P16to upload the voice data toPC for next processing. This paper build FAT12file system in M25P16,so as to the PC canread the data int M25P16in the file form,in stead of reading the data in M25P16in the binaryform.In the end of this paper, it descripes system software optimization methods and examples,which make system software run faster and occupy smaller space.