A nonuniform sampling technique based on inflection point detection and its application to speech coding

Abstract

In order to reduce the data amount, the nonuniform sampling (NUS) method detects samples of a signal, such as local maxima and minima. To overcome the sparseness problem of the NUS method, an inflection point detection (IPD) method is proposed to sample a signal nonuniformly. The IPD samples a signal not only at the local maxima and minima, but also at the inflection points where the slope of the signal changes. To show its usefulness, the IPD is applied to speech coding. The encoder transmits the time instants and sample amplitude values of the inflection points. At the receiver, the decoder estimates the sample amplitude values at the noninflection points by interpolating the received information. Simulation results show that the IPD method produces 7% mean square error improvement over the NUS method. With a small threshold to detect inflection points, the proposed coding method shows 0.38-8.72 dB signal-to-noise ratio (SNR) and 0.5-1.3 mean opinion score improvement, compared to the continuously variable slope delta modulation algorithm (CVSDM). The IPD method produces up to 8.5 dB improvement in SNR over the CVSDM at bit error rates (BER) below 5 × 10(-5), while the IPD method becomes worse than the CVSDM at BER above 5 × 10(-5).

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.…”

“…In non-uniform sampling, a speech is sampled not periodically. Typical examples of the non-uniform sampling method are the local maxima/minima detection method [6,7] and the inflection point (IP) detection method [9][10][11]. The non-uniform sampling methods remove redundancies between samples by extracting irregularly, but the resulting signal shows variable code rate which is not Figure 1.…”

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

“…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.…”