Showing papers on "Code-excited linear prediction published in 1984"
TL;DR: Results of this research indicate that by using adaptive prediction and quantization, intensity and density coded images of high quality can be obtained at information rates as low as 0.7 bits/pixel.
Abstract: This paper summarizes a study on two-dimensional linear prediction of images and its application to adaptive predictive coding of monochrome images. The study was focused on three major areas: two-dimensional linear prediction of images and its performance, implementation of an adaptive predictor and adaptive quantizer for use in image coding, and linear prediction and adaptive predictive coding of density (logarithm of intensity) images. Among the issues investigated are: autoregressive modeling of 2-D image sequences, estimation of the nonzero average bias of the image samples, stability of the inverse prediction error filter, and estimation of the parameters of a 2-D separable linear predictor. The implementation of the adaptive predictor is based on the results of linear predictive analysis. The adaptive quantization of the prediction error signal is done by using a flexible three-level quantizer for code words of fixed or variable length. The above ideas are further applied to density images for exploiting the multiplicative structure of images. The results of this research indicate that by using adaptive prediction and quantization, intensity and density coded images of high quality can be obtained at information rates as low as 0.7 bits/pixel.
134 citations
01 Mar 1984
TL;DR: It is demonstrated that the inclusion of a pitch detector significantly improves the perceived quality of the synthetic speech and a modification of the original algorithm is described, resulting in a lower complexity, and a speech quality close to the results obtained with the original algorithms.
Abstract: We report on the results obtained from simulations of the Multi-Pulse Excitation Coder as proposed by Atal and Remde [4]. We investigated the effects of the different analysis parameters on the resulting synthetic speech signals, using objective and subjective tests. We compared the in [4] proposed sub-optimal solutions with another sub-optimal solution based on an orthogonalization of the solution space and found that the original proposed solutions are reasonable choices. We demonstrate that the inclusion of a pitch detector significantly improves the perceived quality of the synthetic speech. We also describe a modification of the original algorithm, resulting in a lower complexity, and a speech quality close to the results obtained with the original algorithm.
21 citations
01 Jan 1984
TL;DR: If one approximates the vocal tract as a series of fixed length tubes (which is equivalent to representing it as an all-pole digital filter) it becomes possible to predict successive samples of the speech wave as linear combinations of previous samples.
Abstract: If one approximates the vocal tract as a series of fixed length tubes (which is equivalent to representing it as an all-pole digital filter) it becomes possible to predict successive samples of the speech wave as linear combinations of previous samples. The coefficients in the linear combination characterize the shape of the vocal tract. A sequence of sets of coefficients can be used to characterize the changing shape of the vocal tract over time. This representation is widely used because of the particularly efficient algorithms associated with it.
11 citations