In analysis-by-synthesis coders, the delay parameters of pitch predictors in consecutive subframes can be encoded efficiently and decoded robustly if there is a smooth pitch contour. In this paper we present a new method called the windowed search (WS) method to obtain a smooth pitch contour. Three types of WS algorithms are proposed and implemented in CELP coders for experiments. The results show that not only a smooth contour but also less computation and slightly better quality as measured by subjective tests are found by using the WS method as compared to other smoothing methods.

Keywords: CELP coder, pitch predictor, windowed search, smoothed pitch contour, speech coding

Received March 15, 1992; revised September 17, 1992.
Communicated by Lin-Shan Lee.
^*This research has been sponsored by National Science Council of R.O.C. under the contract No. NSC80-0408-E007-16.