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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03 Jul 2007TL;DR: In this article, a system and method for encoding and decoding speech signals that includes a specially-designed Code Excited Linear Prediction (CELP) encoder and a vector quantization (VQ) based Noise Feedback Coding (NFC) decoder was described.
Abstract: A system and method for encoding and decoding speech signals that includes a specially-designed Code Excited Linear Prediction (CELP) encoder and a vector quantization (VQ) based Noise Feedback Coding (NFC) decoder or that includes a specially-designed VQ-based NFC encoder and a CELP decoder. The VQ based NFC decoder may be a VQ based two-stage NFC (TSNFC) decoder. The specially-designed VQ-based NFC encoder may be a specially-designed VQ based TSNFC encoder. In each system, the encoder receives an input speech signal and encodes it to generate an encoded bit stream. The decoder receives the encoded bit stream and decodes it to generate an output speech signal. A system and method is also described in which a single decoder receives and decodes both CELP-encoded audio signals as well as VQ-based NFC-encoded audio signals.
9 citations
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TL;DR: The technique is applied as a preprocessor to improve the intelligibility of the mixed excitation linear prediction (MELP) coder and achieves a level of speech intelligibility comparable to the 8 kb/s G.729 Annex A coder.
Abstract: We recently proposed a technique to increase the robustness of perceptually important acoustic cues in speech, based on modification of the phoneme timing structure. We now apply the technique as a preprocessor to improve the intelligibility of the mixed excitation linear prediction (MELP) coder. The enhancement strategy, however, requires adaptations to minimize the introduction of unnatural speech characteristics that are introduced and intensified by parametric coding schemes. The enhanced 2.4 kb/s fixed-point MELP coder achieves a level of speech intelligibility comparable to the 8 kb/s G.729 Annex A coder.
9 citations
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21 Feb 1995
TL;DR: In this article, a low-delay digital encoder/decoder, based on code excited linear prediction for sound and similar signals, is proposed to provide a low bit speed (generally, 8kbits/s).
Abstract: PURPOSE: To provide a low bit speed (generally, 8kbits/s) and low-delay digital encoder/decoder, based on code excited linear prediction for sound and similar signals. CONSTITUTION: This method is provided with backward adaptive control for the gain of a code book and parameters of a short-term synthesis filter, as well as forward adaptive control for the parameters of a long-term (long-pitch) synthesis filter. By efficient expansion and quantization with a small delay of a pitch parameter, only a general delay corresponding to only a part of delay in a conventional encoding system is allowed to obtain an equivalent sound quality at a lower bit rate.
9 citations
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TL;DR: An interframe differential coding scheme is presented for the line spectrum frequencies (LSF's) to represent the linear predictive coding (LPC) filter of a speech frame.
Abstract: Line spectrum frequencies (LSF's) uniquely represent the linear predictive coding (LPC) filter of a speech frame. In many vocoders LSF's are used to encode the LPC parameters. In this paper, an interframe differential coding scheme is presented for the LSF's. The LSF's of the current speech frame are predicted by using both the LSF's of the previous frame and some of the LSF's of the current frame. Then, the difference resulting from prediction is quantized. >
9 citations
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18 Dec 1995
TL;DR: In this article, a multi-mode CELP encoding and decoding method and device for digitized speech signals providing improvements over prior art codecs and coding methods by selectively utilizing backward prediction for the short-term predictor parameters and fixed codebook gain of a speech signal.
Abstract: The present invention provides a multi-mode CELP encoding and decoding method and device for digitized speech signals providing improvements over prior art codecs and coding methods by selectively utilizes backward prediction for the short-term predictor parameters and fixed codebook gain of a speech signal. In order to achieve these improvements, the present invention provides a coding method comprising the steps of classifying a segment of the digitized speech signal as one of a plurality of predetermined modes, determining a set of unquantized line spectral frequencies to represent the short term predictor parameters for that segment, and quantizing the determined set of unquantized line spectral frequencies using a mode-specific combination of scalar quantization and vector quantization, which utilizes backward prediction for modes with voiced speech signals. Furthermore, backward prediction is selectively applied to the fixed codebook gain in the modes that are free of transients so that it may be used in the fixed codebook search and fixed codebook gain quantization in those modes.
9 citations