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.

Perceptually based and embedded wideband CELP coding of speech.

Abstract: This paper presents a novel multi-band CELP coder with the following characteristics: wideband coding (6.5 kHz), variable bit rate (VBR) coding (10-24 kbps), low-delay (10 ms), embeddibility, and perceptually based dynamic bit allocation. The excitation signal of the linear prediction filter is the vector sum of eight off-line pre-filtered bandpass excitation vectors. The eight excitation codebooks are tree structured, providing embeddibility and variable bit rate. The dynamic allocation of the bitstream among the different bands is based on the perceptual importance of each band. The multi-band and perceptual structure of the coding scheme results in graceful degradation with decreasing bit rates both in quiet and in the presence of background noise.

Optimization algorithm for the MP-MLQ excitation in G723.1 encoder

Abstract: It is known that the optimization algorithms of the excitations can be considered as one of the most difficult parts from a code excited linear prediction (CELP) based encoder. This paper presents an original detailed, rigorous and gradual analysis of the optimization algorithm for the MP-MLQ excitation, which characterizes the high-rate working mode of the ITU-T G723.1 encoder. The complete derivation of the algorithms presented here with various comments and accompanying explanations, allow an ordinary DSP programmer to efficiently implement and debug his encoding software.

Encoding apparatus, decoding apparatus, encoding method, and decoding method for adjusting a spectrum amplitude

Abstract: An encoding device is provided for increasing the quality of an encoded signal, even when encoding music signals. In the encoding device, a Code-Excited Linear Prediction (CELP) encoder generates first encoded data by encoding an input signal, and a CELP decoder generates a decoded signal by decoding the first encoded data input from the CELP encoder. Additionally, a characteristic parameter encoder calculates a parameter that expresses the degree of fluctuation in the ratio of the peak components and the floor components between the spectra of the decoded signal and the input signal.

A Packet Loss Concealment Algorithm Robust to Burst Packet Loss Using Multiple Codebooks and Comfort Noise for CELP-Type Speech Coders

Abstract: In this paper, a packet loss concealment (PLC) algorithm for CELP-type speech coders is proposed to improve the quality of decoded speech under burst packet loss. A conventional PLC algorithm is usually based on speech correlation to reconstruct decoded speech of lost frames by using the information on the parameters obtained from the previous frames that are assumed to be correctly received. However, this approach is apt to fail to reconstruct voice onset signals since the parameters such as pitch, LPC coefficient, and adaptive/fixed codebooks of the previous frames are almost related to silence frames. Thus, in order to reconstruct speech signals in the voice onset intervals, we propose a multiple codebook based approach which includes a traditional adaptive codebook and a new random codebook composed of comfort noise. The proposed PLC algorithm is designed as a PLC algorithm for G.729 and its performance is then compared with that of the PLC algorithm employed in G.729 by means of perceptual evaluation of speech quality (PESQ), a waveform comparison, and an A-B preference test under different random and burst packet loss conditions. It is shown from the experiments that the proposed PLC algorithm provides significantly better speech quality than the PLC of G.729, especially under burst packet loss and voice onset conditions.