This paper describes the design of a toll-quality 4-kbit/s speech coder based on phase-adaptive PSI-CELP. This adaptation method not only gives pitch periodicity to the random excitation but also synchronizes the basic point of the stored random vector with the pitch phase. We further improve the proposed coder by introducing a backward gain prediction scheme. In subjective evaluation experimen...

In this paper, we propose a new coder based on the algebraic CELP(ACELP) coding technique. Our goal is to improve the quality of the obtained synthetic speech by a modification of the excitation signal of the classical coder. Such modification is accomplished by the variation of both the positions of the excitation impulses, and their amplitudes. The proposed algorithm consists of dividing the ...

In this paper we present a study of channel optimized ma­ trix quantizer (COMQ) applied to quantize LSP parameters in a CELP (Code Excited Linear Prediction) coder. A mod­ ification of the DoD FS-1016 standard [2} is used for this purpose. A Gaussian channel is considered as the channel through which information is sent and BPSK (Binary Phase Shift-Keying) is used as modulation technique. To me...

The idea of applying vector quantization (VQ) to linear prediction coding (LPC) to realize a very low bit-rate speech coder with reasonable speech quality is investigated in this research. Instead of encoding LPC parameters directly, line spectral frequency (LSF) coefficients are obtained through a transformation of LPC and then encoded via VQ in the proposed scheme. In order to utilize the int...

This paper presents an efficient analysis-by-synthesis vector quantizer for the dispersion phase of the excitation signal which was used to enhance a waveforminterpolative coder. The scheme can be used to enhance other harmonic coders, such as the sinusoidal-transform coder and the multiband-excitation coder. The scheme incorporates perceptual weighting, and does not require any phase unwarping...

This paper presents an algorithm that jointly optimizes a lattice vector quantizer (LVQ) and an entropy coder in a subband coding at all ranges of bit rate. Estimation formulas for both entropy and distortion of lattice quantized subband images are derived. From these estimates, we then develop dynamic algorithm optimizing the LVQ and entropy coder together for a given entropy rate. Compared to...

Wavelet-based image coders optimally represent smooth regions and isolated point singularities. However, w av elet coders are less adept at representing perceptually important edge singularities, and coding performance su ers signi cantly as a result. In this paper, w epropose a no veltw o-stageimage coder framework based on modeling images as edge cartoons + textures. In stage 1, w einfer and ...

Based on the standard fractal transformation in spatial domain, simple relations may be found relating coefficients in detail subbands in the wavelet domain. In this work we evaluate a hybrid wavelet-fractal image coder, and we test its ability to compress radiographic images of weld defects. A comparative study between the hybrid coder and standard fractal compression technique have been made ...