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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11 Jun 1991TL;DR: The authors review the CELP (code excited linear prediction) coding algorithm, and the efforts recently made for improving the performance and reducing the complexity.
Abstract: The authors review the CELP (code excited linear prediction) coding algorithm, and the efforts recently made for improving the performance and reducing the complexity. The efforts for improving the coding performance have been aimed not only at making the quality better, but also at further reducing the bit rate without degrading the quality. A sparse-delta codebook is introduced as an example of a codebook with a computationally efficient structure. Multimode coding is then described for improving the perceptual quality of CELP at low bit rates. >
5 citations
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TL;DR: Both the objective and subjective tests show that the subjective quality of the synthesized clean speech coded by the proposed 8.4-kbps wideband MELP coder is comparable to that of the ITU G.722 coding standard for digital transmission of wideband audio signals.
5 citations
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23 Mar 1992TL;DR: The authors examined the possibility of replacing the fixed stochastic codebook by an adaptive codebook with adaptation based on the characteristics of the unquantized residual, and suggested that adaptation methods based only on the spectral magnitude are unlikely to result in significant improvement.
Abstract: Speech codecs based on code excited linear prediction (CELP) traditionally use an adaptive short-term filter, an adaptive codebook (long-term filter), and a fixed (stochastic) excitation codebook. The authors examined the possibility of replacing the fixed stochastic codebook by an adaptive codebook with adaptation based on the characteristics of the unquantized residual. In a typical 4-kb/s CELP codec, the authors use the spectral magnitude and phase of the unquantized residual to experimentally estimate an upper bound on the performance improvement which could be obtained by excitation codebook adaptation. The results suggest that adaptation methods based only on the spectral magnitude (including fractal-based codebooks) are unlikely to result in significant improvement. Adaptation based on the spectral phase information, on the other, shows a significant potential for improving CELP speech quality. The authors also present results of a preliminary test designed to investigate the effect of quantization noise on phased-based adaptation of excitation codebooks. >
5 citations
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13 Jun 1988TL;DR: The vector-quantized transform coder is proposed as an alternative to a code-excited linear predicting (CELP) coder and requires substantially fewer computations than CELP, which makes the VQTC attractive for real-time applications.
Abstract: The vector-quantized transform coder (VQTC) is proposed as an alternative to a code-excited linear predicting (CELP) coder. The consideration of more efficient and subjectively meaningful residual quantization allows the VQTC to operate at rates as low as 6 kb/s without significant degradations in speech quality. Below 6 kb/s the quality of the speech was good and did not contain any background noise peculiar to transform coders. Simulations of the VQTC and standard CELP were performed to assess the performance of the VQTC as an alternative coding scheme for low bit rates. In general, the performance of the VQTC was as good as CELP at rates of 9 to 4.8 kb/s. However, the VQTC requires substantially fewer computations than CELP, which makes the VQTC attractive for real-time applications. >
5 citations