Objective Speech Quality Assessment Based On P.563

With the continuous development and popularization of various multimedia services, to measure the quality of multimedia services has gradually become a hot issue. Voice service is of vital importance in the multimedia communication system, which determines the efficiency of communication between human beings directly. Methods for speech quality assessment can be mainly divided into two classes which are subjective evaluation and objective evaluation. Subjective evaluation of speech quality is time-consuming and expensive while it has higher reliability.In the contrast, objective quality assessment is quite simple and quick, but its accuracy of evaluation is much lower.The P.563is the first single-ended method for objective speech quality assessment established by the International Telecommunication Union. But the designing of algorithm in the P.563has some defects, which limit the scope of its application. In this paper, the P.563algorithm is improved from three aspects respectively, which are the pre-processing of speech, feature extraction of speech and the mapping model of evaluation result. Besides, a portable system for objective evaluation of speech quality is developed based on RealV210.Firstly, to detect the single-frequency noise in the speech based on the properties of its spectrum distribution during the pre-processing stage which aims to improve the predicting accuracy of the P.563for speech with single-frequency noise.Secondly, the Mel-Frequency Cepstral Coefficients (MFCCs) are extracted from undegraded speech signal which reflect the perception of human beings’ audio system, and build a Gaussian Mixture Model (GMM) for them.Thirdly, to build six kinds of reference models for6types of speech distortion using GMM and determine the distortion type of speech according to the distance between the feature vector and these reference models. Build the mapping relation between the multidimensional characteristic of speech and the result of objective evaluation.Finally, design and develop a set of portable system for objective assessment of speech quality based on RealV210, the system has two operating modes which are the self-inspection mode and the real-time speech quality evaluation mode.As to the speech database for testing built in this paper, the correlation between results of subjective evaluation and results of the algorithm in this paper is improved from0.44to0.82, which shows the favorable performance.