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.

Method and apparatus for speech coding

Abstract: A speech encoding method and apparatus for encoding a speech according to code-excited linear prediction CELP, comprising: analyzing the speech to obtain a linear prediction parameter; obtaining a linear prediction parameter code by encoding the linear prediction parameter; obtaining an adaptive code vector concerning an adaptive code from an adaptive codebook; obtaining pitch information corresponding to the adaptive code; evaluating a noise level of the speech based on the pitch information; obtaining a weight based on the evaluated noise level; obtaining an excitation code by comparing a coded speech and the speech, wherein the coded speech is obtained by using the adaptive code vector, an excitation codebook and the weight; and outputting a speech code including the adaptive code, the linear prediction parameter code, and the excitation code.

Proposed Modifications in the Excitation Codebook Structure of ITU-T CS-ACELP Speech Codec and Its Overall Comparative Performance Analysis with CELP-Based AMR-NB Speech Codec

Abstract: The paper addresses the tactic of using forward mode excitation codebook structure of extended G.729 (ITU-T. Recommendation, 2007 [1]) consuming two non-zero pulses in each track in ITU-T 8 Kbps CS-ACELP speech codec (ITU-T. Recommendation, 2007 [1]). The proposed modification in legacy speech codec for determining optimized excitation codebook codevector using least significant search engine avoids two different codebook structures to minimize the complexity of search engine. Modification in the excitation codebook structure of the legacy speech codec triggers the bit rate of 11.6 Kbps. Comparative performance analysis is performed between the proposed speech codec and CELP-based speech codec using different subjective and objective quality assessment parameters.

Trellis code excited linear prediction (TCELP) speech coding

Abstract: This paper describes extensions to trellis-based scalar-vector quantization (TB-SVQ) , as novel techniques for coding sources with memory. These techniques are proposed as efficient solutions for the quantization of the excitation in Code-Excited Linear Predictive (CELP) coding algorithms. A new 24 kbit/s low-delay trellis CELP (LD-TCELP) coder is introduced which achieves high-performance coding of narrowband speech with an algorithmic delay of only 3 ms. This coder utilizes the granular structure of the underlying trellis code and the codebook shaping capability of the SVQ approach to effectively capitalize on the gain of higher dimensional (24-D) vector quantization. We present experimental results which show that the LD-TCELP coder outperforms two toll-quality standardized coders: ITU-T G.728 16 kbit/s LD-CELP and ITU-T G.726 32 kbit/s ADPCM. The proposed LD-TCELP coder can also utilize a low-complexity codebook search approach with a computational complexity that is about 75% of that of ITU-T G.728 LD-CELP.

Codebook excited linear prediction encoder, decoder, and methods for encoding and decoding

Abstract: The inventin provides a codebook excited linear prediction encoder, a decoder, and methods for encoding and decoding. In accordance with a first aspect of the present invention, bitstream elements of sub-frames are encoded differentially to a global gain value so that a change of the global gain value of the frames results in an adjustment of an output level of the decoded representation of the audio content. In accordance with another aspect, a global gain control across CELP coded frames and transform coded frames is achieved by co-controlling the gain of the codebook excitation of the CELP codec, along with a level of the transform or inverse transform of the transform coded frames. According to even another aspect, a variation of the loudness of a CELP coded bitstream upon changing the respective gain value is rendered more well adapted to the behavior of transform coded level adjustments, by performing the gain value determination in CELP coding in the weighted domain of the excitation signal.

CELP coding with adaptive excitation codebooks

Abstract: Code-excited-linear-predictive (CELP) coding has led to speech coding schemes with a good speech quality at 8 kb/s and a fair quality at data rates of about 4.8 kb/s. In the present work, the authors propose a novel method for improving the speech quality of a CELP codec at low bit rates by adaptation of the excitation codebook (ACELP). The adaptive cookbook consists of a set of basic excitation vectors which are adapted to an analysis speech frame by calculating optimum amplitude values. The amplitudes are quantized and encoded at a very low bit rate using a gain shape vector quantizer. The results of simulation experiments show that the mean squared error by CELP with an adaptive codebook is substantially lower than that of CELP with a fixed stochastic codebook. In informal listening tests the quality of the speech processed by the adaptive CELP scheme was superior and less speaker-dependent compared to a conventional CELP scheme. >