Topic
Code-excited linear prediction
About: Code-excited linear prediction is a research topic. Over the lifetime, 2025 publications have been published within this topic receiving 28633 citations. The topic is also known as: CELP.
Papers published on a yearly basis
Papers
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15 Mar 1999
TL;DR: This paper presents a harmonic+noise speech coder which uses an efficient spectral quantization technique and a novel voiced/unvoiced (V/UV) mixing model which allows noise to be added in the harmonic portion of speech spectrum so that buzzyness is reduced.
Abstract: This paper presents a harmonic+noise speech coder which uses an efficient spectral quantization technique and a novel voiced/unvoiced (V/UV) mixing model. The harmonic magnitudes are coded at 23 bits/frame using the magnitude response of a linear predictive coding (LPC) system. The difference between the harmonic magnitudes and the sampled magnitude response is minimized by the closed-loop approach. The V/UV mixing is modeled by a smooth function which is derived from the speech spectrum envelope based on the flatness measure. The V/UV mixing model allows noise to be added in the harmonic portion of speech spectrum so that buzzyness is reduced. The V/UV mixing information is determined from the spectral parameters available in the decoder, no bits are needed for transmitting the V/UV information. A 1.4 kbps harmonic coder is developed. The speech quality of the coder is comparable to other harmonic coders operating at higher rates.
9 citations
Patent•
21 Dec 2015
TL;DR: In this paper, an apparatus for reconstructing a frame including a speech signal as a reconstructed frame is provided, the apparatus including a determination unit and a frame reconstructor being configured to reconstruct the reconstructed frame.
Abstract: An apparatus for reconstructing a frame including a speech signal as a reconstructed frame is provided, the apparatus including a determination unit and a frame reconstructor being configured to reconstruct the reconstructed frame, such that the reconstructed frame completely or partially includes the first reconstructed pitch cycle, such that the reconstructed frame completely or partially includes a second reconstructed pitch cycle, and such that the number of samples of the first reconstructed pitch cycle differs from a number of samples of the second reconstructed pitch cycle.
9 citations
01 Nov 2012
TL;DR: An analysis by synthesis coder using a CS based excitation sequence framework is developed and the encoder is shown to scale gracefully with CS dimension and offers a mechanism for quality to bit rate trade off.
Abstract: Code-excited linear prediction (CELP) is one of the most commonly used approaches for speech compression The CELP coder, in particular the ACELP coder, relies on extracting an appropriate excitation sequence that is passed through a long-term and short-term linear prediction filter to synthesize the speech One limitation of the analysis-by-synthesis search methods employed in the ACELP coder is that the positions of the non-zero entries in the excitation sequence and their gains are limited Increasing the richness of the excitation to improve the speech quality is not only accompanied by the usual increase in the bit rate but also by a significant increase in search complexity We propose dealing with this scalability issue by using tools from the compressed sensing (CS) domain An analysis by synthesis coder using a CS based excitation sequence framework is developed and the encoder is shown to scale gracefully with CS dimension and offers a mechanism for quality to bit rate trade off
9 citations
01 Jun 1996
TL;DR: Direct comparisons of MLPs and linear filters show that with CELP degradation the SNR improvements achieved by the MLP is measurably better than with an equivalent linear structure but when the degradation is additive noise the two structures perform equally well.
Abstract: A multilayer perceptron (MLP) is applied as a time domain nonlinear filter to two classes of degraded speech, namely gaussian white noise and nonlinear system degradation introduced by a low bit-rate CELP coder. The goal of the study is to examine the influence of the inherent nonlinearity within the MLP, and this is achieved by varying the levels of nonlinearity within the structure. Direct comparisons of MLPs and linear filters show that with CELP degradation the SNR improvements achieved by the MLP is measurably better than with an equivalent linear structure (3 dB cf 1.5 dB) but when the degradation is additive noise the two structures perform equally well. The study highlights the importance of scaling to achieve optimum performance, and of matching the enhancer to the degradation.
9 citations
13 Nov 1994
TL;DR: It is pointed out that a prevalent form of fractal image coding can be viewed as a kind of generalized predictive coding, and several directions for codec design are outlined, among which are short-term prediction and transform coding or vector quantization of prediction residuals.
Abstract: We point out that a prevalent form of fractal image coding can be viewed as a kind of generalized predictive coding. Several key issues in predictive coding are the prediction gain, the design of codebooks for predictors and prediction residuals, shaping of reconstruction errors, and codec complexity. Fractal coding can yield higher prediction gains than conventional predictive coding by its use of noncausal predictors and long-term predictors. However, noncausal prediction necessitates iterative decoding and long-term predictors require search over a large area, both of which increase codec complexity. Design of predictors and prediction codebooks for fractal coding has relied much on heuristics. Drawing on known results about predictive coding, we outline several directions for codec design, among which are short-term prediction and transform coding or vector quantization of prediction residuals. Shaping of reconstruction errors by noise-feedback or analysis-by-synthesis coding may also be beneficial. >
9 citations