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.
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20 May 2004
TL;DR: In this paper, a method of searching a codebook of a code excited linear prediction (CELP) vocoder using an algebraic codebook is provided to search the algebraic CELP vocoder with a small amount of calculations using a search tree restricting method.
Abstract: PURPOSE: A method of searching a codebook of a code excited linear prediction (CELP) vocoder using an algebraic codebook is provided to search the algebraic codebook with a small amount of calculations using a search tree restricting method CONSTITUTION: A method of searching an algebraic codebook of an algebraic CELP vocoder using a depth-first tree search method includes a step(100) of searching up to a specific level of trees in order to predict a tree where an optimum pulse is positioned, a step(200) of selecting a predetermined tree according to the search result and removing other trees, and a step(300) of searching only the selected tree to select an optimum algebraic code
3 citations
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21 Apr 1997TL;DR: A new 4 kbit/s speech coder based on CELP structure with 45 ms total codec delay is proposed to get high quality speech at low bit rate and techniques of formant enhancement in the spectral envelop and harmonic recovery in the transient region are introduced to reduce buzzy and hoarse sounds.
Abstract: This paper proposes a new 4 kbit/s speech coder based on CELP structure with 45 ms total codec delay. The coder is mainly featured by the renewal codebook of the excitation signal and the linked split-vector quantizer of line spectrum pair parameters which enable the coder to get high quality speech at low bit rate. In addition, techniques of formant enhancement in the spectral envelop and harmonic recovery in the transient region are also introduced to reduce buzzy and hoarse sounds, respectively. From the intensive listening test with intermediated response system (IRS) speech, we obtained a comparable subjective quality to 32 kbit/s ADPCM (ITU Recommendation G.726) under a nominal speech input level of -26 dB overload.
3 citations
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14 Nov 1994TL;DR: The authors present a low delay speech coder operating at 4.8 kb/s which provides good speech quality with a coding delay only about 2.5 msec and adopts a new approach to predict the long term prediction (LTP) coefficients based on a "dual-decision" scheme.
Abstract: Low-delay speech coding has drawn much attention because of its many potential applications. A lot of low delay speech coders have been proposed in the past few years. But almost all of them focus on the speech bit rate between 8 kb/s to 16 kb/s. The authors present a low delay speech coder operating at 4.8 kb/s which provides good speech quality with a coding delay only about 2.5 msec. This new low delay coder uses backward LPC analysis to remove the short-term correlation from speech and adopts a new approach to predict the long term prediction (LTP) coefficients based on a "dual-decision" scheme. At the excitation part, the authors exploit a new excitaton model which contains a sinusoid signal codebook and a stochastic codebook to excite the whole speech system. The synthesized speech of this coder has comparable quality to that of FS-1016 CELP coder while having a delay constraint more than an order of magnitude smaller than that of the FS-1016 coder. >
3 citations
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11 Apr 2007TL;DR: An improved efficiency perceptual audio codec is presented which analyzes each block of input signal and selects a suitable time/frequency mapping transform for it, compared with the widely famous MPEG-1 Layer-III algorithm.
Abstract: An improved efficiency perceptual audio codec is presented which analyzes each block of input signal and selects a suitable time/frequency mapping transform for it. The selection is based on statistics of the input signal vis-a-vis energy compaction and resolution power properties of the transforms employed which include the DFT (uniform subbands), DFT (critical subbands), DCT and CELP( for speech only blocks). The performance of the codec is compared with the widely famous MPEG-1 Layer-III algorithm. Efficiency enhancement is indicated by improved grades of subjective listening test for the proposed codec compared to those for MPEG-1 Layer-III at similar bit rates.. The paper concludes with a discussion of future research implications of the work.
3 citations