Kiyoshi Mizui

Variable bit rate modulo-PCM using adaptive predictor

The authors propose an improved variable bit rate modulo-PCM (VBR-MPCM). It has the same performance as conventional VBR-MPCM, but it has lower complexity and shorter time delay. The authors also propose variable bit rate modulo-PCM using adaptive predictor (VBR-MPCM-AP) which differs in that it has an adaptive rather than fixed predictor. Its performance is about 0-3 dB better than that of improved VBR-MPCM.<<ETX>>

Application of road-to-vehicle communication and ranging system using spread spectrum technique to ADS

As a solution to traffic congestion, ADS (Advanced Demand Signals scheme) which controls a traffic light by passing vehicles has been proposed. However it is assumed that this system correctly obtains the relative distance between each vehicle and the traffic signal through the information from vehicles. This paper discusses the application of road-to-vehicle communication and ranging system using spread spectrum technique to ADS.

Variable bit rate modulo-PCM with multi-quantizer

The authors propose variable bit rate modulo-PCM with multiquantizer (VBR-MPCM-MQ), which applies the multiquantizer method to VBR-MPCM using an adaptive predictor (VBR-MPCM-AP) for selecting optimum step size. In VBR-MPCM-MQ, modulo amplitude, quantization bits, and step size are adaptively varied every block in order to prevent anomaly error and to increase data compression efficiency. By computer simulation, it is confirmed that the proposed VBR-MPCM-MQ has better performance by about 2 dB in both SQNR and segmental SQNR (SQNR seg) than conventional VBR-MPCM-AP. It is confirmed that the performance of VBR-MPCM-MQ is better by about 12 dB in SQNR and about 3 dB in SQNR seg than that of the conventional ADPCM (adaptive differential PCM) recommended by CCITT.<<ETX>>

Modulo-PCM with multi-quantizer

In this paper, we propose a Modulo-PCM with Multi-Quantizer (MPCM-MQ) which has high data compression efficiency because the proposed MPCM-MQ scheme can get rid of the anomaly errors by utilizing the multiquantizer method. By using this proposed scheme, we can improve its performance by about 10 [dB] ∼ 15 [dB] (1.5 [bits/sample] ∼ 1.8 [bits/sample]) in SQNR compared with the conventional MPCM-AQF scheme.

Variable bit rate modulo‐pcm using adaptive predictor

Recently, Modulo-PCM (MPCM) was proposed as one of the waveform speech coding schemes. The MPCM is considered to be a possible alternative to the DPCM. This is because the MPCM has only granular noise without overload although it has the “anomaly errors” instead of the overload noise. The variable bit rate modulo-PCM (VBR-MPCM) has been proposed which applies the variable rate coding method to the Modulo-PCM. This paper proposes the improved variable bit rate modulo-PCM (improved VBR-MPCM) whose performance is the same and whose complexity is about half compared with that of the conventional VBR-MPCM. Moreover, the variable bit rate modulo-PCM using adaptive predictor (VBR-MPCM-AP) also is proposed which uses second-order pole and sixth-order zero adaptive predictors instead of the fixed ones used in the improved VBR-MPCM. From the computer simulation results, it is confirmed that the VBR-MPCM-AP is about 0 to 8 dB in segmental SQNR (SQNRseg), which is better than the conventional VBR-MPCM, MPCM-AQF and ADPCMs. From the listening test results, it is also confirmed that the proposed VBR-MPCM-AP is able to obtain good reconstructed speech.

Variable bit rate PARCOR-VQ hybrid Vocoder

The variable bit rate PARCOR-VQ hybrid vocoder uses the PARCOR scheme for unvoiced or transient periods and the VQ (vector quantization) scheme for voiced periods with a variable bit rate method. The ratio of voiced periods is much higher than that of unvoiced periods. Thus, it is expected that the average bit rate of the proposed vocoder will be much lower than that of the PARCOR vocoder. With respect to the accuracy of analysis-synthesis for unvoiced periods (important for recognition of words), the proposed vocoder is better than the VQ vocoder because it uses the PARCOR scheme for its periods. It is also expected that reconstructed speech of the proposed vocoder will be higher than that of the VQ vocoder. By computer simulation and listening tests, it was confirmed that the proposed vocoder, whose average bit rate is 919 b/s, has nearly the same quality as the 2.4 kb/s PARCOR vocoder.<<ETX>>