SC pitch extraction for real‐time and continuous processing
Shinsuke Yamashita, Akio Ogihara, Shojiro Yoneda · Electronics and Communications in Japan (Part III Fundamental Electronic Science) · 1992
Abstract If speech recognition is applied to man‐machine interface, real‐time processing is naturally desired. It is efficient for real‐time processing that routine preprocesses (extraction of features and analysis) are executed with custom hardware. This paper proposes two kinds of pitch extractors which continuously extract the fundamental period of an input signal in real time. Since the pitch extractors are constructed using the switched capacitor (SC) technique, they can be integrated into an LSI package. The first SC pitch extractor is based on the autocorrelation function, and the extractor calculates two variable multiplication with a programmable capacitor array. The second SC pitch extractor is based on the absolute difference function which is obtained by replacing the multiplication in the autocorrelation function with subtraction, and the absolute difference function is useful to reduce circuit scale. A remarkable feature of both SC pitch extractors is that the pitch period of an input signal is continuously extracted in real time. Hence the pitch synchronous analyzer which performs spectral analysis in real time can be constructed with the proposed SC pitch extractors and the SC DFT circuit. According to the experimental results, the error of the SC pitch extractors made with discrete parts is less than 3.0 percent. In addition, the proposed SC pitch extractors were applied to five Japanese vowels and obtained a satisfactory result.