Mixed Encoding Speech Enhancement Method

With the development of digital technique and the persistent increase of requirement of speech communications, application of digital speech coding is more widely, especially in the area of visible telephone, digital cellular mobile communication, public switched telephone network and packet transfer voice system, etc. Premised on assurance of speech quality, digital speech coding can reduce rate of bits, for the purpose of increasing use of finite bandwidth.Speech is depicted by its sample in time-domain, or is depicted by its parameter-character. Take the difference between them as the basis, speech coding could also be divided into waveform coding and parameter coding, which are represented by two typical methods CVSD and AMBE, correspondingly. Communication work very well using each of them separately. But in some applications there's need of using both of them in the series connect way and make the intelligibility of speech have a obvious descend. Thus have to find one specific way to strengthen the speech thereinto, keeping the inter intelligibility at a high level, which is also the main work in this dissertation.Whole paper is made up of five chapters. The development course and tendency of speech compress coding, and the basic methods of processing speech is introduced in the first two chapters.On the basis of analysis and research the working theory of CVSD and AMBE, and the reason the intelligibility descend, a specific strengthen arithmetic which is based on estimate of keynote periods using the SMDSF method and taken the strengthen arithmetic within Minimum-Phase Harmonic speech coder as reference is narrated.The strengthen arithmetic in this dissertation is realized by TI's DSP TMS320VC5509. The design of hardware is introduced in the third chapter meanwhile the software containing common method of developing program for DSP and the realization of the strengthen arithmetic itself is introduced in the fourth chapter. In the fifth chapter the systemic debugging process and result of the processing is introduced.