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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
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Proceedings ArticleDOI
14 Apr 1991
TL;DR: The author describes an efficient model of the excitation signal of a CELP (code excited linear prediction) coder, capable of reducing significantly the corresponding bit rate while maintaining a good subjective quality.
Abstract: The author describes an efficient model of the excitation signal of a CELP (code excited linear prediction) coder, capable of reducing significantly the corresponding bit rate while maintaining a good subjective quality. This topic is of paramount importance since, typically, in CELP coders the greater part of the available bit rate is allocated to encode the excitation signal. The model has been improved by resorting to (1) a dual loop algorithm to compute pitch lags; (2) a codebook of excitation vectors designed by a covering method; and (3) a combined backward/forward adaptive estimator to track the excitation gain. Numerical results and listening tests show that this excitation model overcomes the typical deficiencies of CELP coders at low bit rates. In particular, the proposed approach makes it possible to reduce the excitation rate of a stochastic CELP coder by 20% while at the same time improving the speech quality in voiced speech. >

7 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated how standard speech coders, currently used in modern communication systems, affect the quality of the speech of persons who have common speech and voice disorders.
Abstract: We investigated how standard speech coders, currently used in modern communication systems, affect the quality of the speech of persons who have common speech and voice disorders. Three standardized speech coders (GSM 6.10 RPE-LTP, FS1016 CELP, and FS1015 LPC) and two speech coders based on subband processing were evaluated for their performance. Coder effects were assessed by measuring the quality of speech samples both before and after processing by the speech coders. Speech quality was rated by 10 listeners with normal hearing on 28 different scales representing pitch and loudness changes, speech rate, laryngeal and resonatory dysfunction, and coder-induced distortions. Results showed that (a) nine scale items were consistently and reliably rated by the listeners; (b) all coders degraded speech quality on these nine scales, with the GSM and CELP coders providing the better quality speech; and (c) interactions between coders and individual voices did occur on several voice quality scales.

7 citations

Patent
07 Jan 2002
TL;DR: In this paper, a random code vector reading section was replaced with an oscillator for outputting different vector streams in accordance with values of input seeds, and a seed storage section for storing a plurality of seeds.
Abstract: A random code vector reading section and a random codebook of a conventional CELP type speech coder/decoder are respectively replaced with an oscillator for outputting different vector streams in accordance with values of input seeds, and a seed storage section for storing a plurality of seeds. This makes it unnecessary to store fixed vectors as they are in a fixed codebook (ROM), thereby considerably reducing the memory capacity.

7 citations

Proceedings ArticleDOI
21 Apr 1997
TL;DR: The object of this paper is to describe the first stage of the construction of a proposed three-layer model for speech quality assessment and to define four main perceptual dimensions to be used in the second layer of the proposed model.
Abstract: Digital telecommunication networks may involve a multiple number of public switched telephone networks (PSTN), cellular and mobile systems and to some extent also satellite systems. Most of these networks contain non-linear speech coders and other speech algorithms which may degrade the overall end-to-end quality of speech. An important problem is how to assess the speech quality of such compounded systems. The object of this paper is to describe the first stage of the construction of a proposed three-layer model for speech quality assessment. A subjective test of the speech quality of 16 different compounded transmission paths (mixtures of PCM, GSM full and half rate, DECT, CELP, LD CELP, FS10-16) is carried out by 40 subjects using 21 different rating scales. The main result of this paper is the test results which lead to the definition of four main perceptual dimensions to be used in the second layer of the proposed model.

7 citations

Proceedings ArticleDOI
16 Mar 2008
TL;DR: The perceptual evaluation of speech quality and enhanced modified bark spectral distortion tests under various packet loss conditions confirm that the proposed algorithm is superior to the concealment algorithm embedded in the G729.
Abstract: In this paper, we propose a method for packet loss concealment (PLC) based on time scale modification for code excited linear prediction (CELP) based coders in packet network. We perform a time scale modification (TSM) using a waveform similarity overlap-add (WSOLA) technique which is an interpolation-based method operating entirely in the time domain, to reconstruct the excitation signal of the lost frame. We applied the proposed scheme to the standard ITU-T G729 standard speech coder to evaluate the proposed method. The perceptual evaluation of speech quality (PESQ) and enhanced modified bark spectral distortion (EMBSD) tests under various packet loss conditions confirm that the proposed algorithm is superior to the concealment algorithm embedded in the G729.

7 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20226
20213
20207
201915
201810
201713