On a new vocoder technique by the nonuniform sampling

Abstract

To reduce the redundancy within samples that resulted from uniform sampling method like E M , n o n d o r m sampling or nonredundant-sample coding methods can be considered. However, it is well known that when conventional nonuniform sampling methods are applied directly to speech signal, the required amount of data is comparable to or more than that of uniform sampling method. To overcome this problem, a new nonunifom sampling method is proposed, in which nonuniform sampling is applied to the low-pass filtered speech signal and the remain signals are compensated by 16 colored Gaussian random noises with various noise levels. By this method, speech signal waveform can be encoded by 1.8 times larger compression ratio than that of the conventional nonuniform sampling method.

A Fixed Rate Speech Coder Based on the Filter Bank Method and the Inflection Point Detection

“…Non-uniform sampling technique is an alternative to overcome the information redundancy due to the high correlation between neighboring speech samples [5][6][7][8][9][10][11]. In non-uniform sampling, a speech is sampled not periodically.…”

A Low Bit Rate Speech Coder Based on the Inflection Point Detection

“…As shown in the figure, there are several types of inflection points: local maxima (point b), local minima (point a), and points of simple slope changes (point c). Non-uniform sampling techniques was proposed to detect these local maxima and minima to reduce the number of samples [5,6]. Later, a method to detect the points showing slope changes (points a, b, c in Figure 1) was presented for speech coding [9].…”

“…The speech coder based on the non-uniform sampling technique shows variable data rate which is not suitable for communication application [5,6,11,12]. In this paper, a new fixed and low bit rate speech coder is proposed based on the IPD.…”

“…The non-uniform sampling is a research area studied as an alternative to the conventional uniform sampling technique [5][6][7][8][9][10][11][12]. Due to less frequent sampling, the non-uniform sampling based speech coding shows lower bit rate than the PCM coding based on the uniform sampling.…”

“…Due to less frequent sampling, the non-uniform sampling based speech coding shows lower bit rate than the PCM coding based on the uniform sampling. The non-uniform sampling is achieved by detecting local maxima and minima of a signal [5,6] or inflection points of a signal [11,12]. Since the number of maxima, minima and inflection points is variable depending on a signal, the bit rate of the non-uniform sampling based speech coder is not fixed.…”