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.

Analysis and quantization procedures for a real-time implementation of a 4.8 kb/s CELP coder

Abstract: The main results from work on analysis techniques and quantization procedures for real-time implementation of the Proposed Federal Standard 1016 4800-b/s voice coder developed by the US DoD and AT&T Bell Laboratories are presented. Reduced search procedures are described for the adaptive and stochastic codebooks, two basic functions in code-excited linear predictive coders (CELPs), where great computational effort is required. An efficient procedure for the joint computation and quantization of the line spectrum pair (LSP) is also proposed. Details about a preliminary real-time implementation on a commercial board with a single DSP32C processor are described. >

A 450bps Speech Coding Algorithm Based on Multi-Mode Matrix Quantization

Abstract: A 450bps speech coder based on multi-frame structure and multi-mode matrix quantization is presented. The multi- frame structure consisting of four frames is adopted to reduce the algorithm delay. The parameter matrices are classified into different modes based on the voicing vector information of superframe. To improve speech quality, a dynamic bit allocation scheme is developed. Experimental results show that the speech quality of the proposed vocoder is intelligible with good naturalness.

On the improvement of scalable MPEG-4 CELP at low bitrate

Abstract: CELP (code-excited linear predictive), one of the speech coding techniques, is a part of the MPEG-4 standard. The distinct feature of the MPEG-4 CELP is that it has the bitrate and bandwidth scalability for different users with different network bandwidth. However, subjective experiments show that the scalable mechanism of the MPEG-4 CELP does not perform well at low core bitrates, e.g., 3.85 kbps. In this paper, we propose a method to generate the enhancement information that it better suited for low core bitrates. Experimental results show that the proposed approach has a better coded quality or such a situation.

A 4.2 kb/s low-delay speech coder with modified CELP

Abstract: In this letter, we propose a low-delay speech coder at 4.2 kb/s. In the proposed coder, we remove short-term prediction and use three-tap long term prediction to exploit the speech redundancy. A "dual-decision" pitch estimation algorithm and an adaptive sinusoidal excitation codebook are introduced to improve the performance of the proposed coder. The synthesized speech of this coder has comparable quality to that of conventional CELP coders at similar bit rates, while it has a coding delay of only 5 ms.

Wavelet linear prediction vocoder based on auditory model

Abstract: It is very difficult but very important to get higher quantity at lower bit rate in the field of speech coding. Traditional vocoders, such as LPC10e and CELPC, can give acceptable results but suffer from a hoarse output. We attribute this problem to the inconsistency between the equal resolution characteristic of linear prediction throughout the whole frequency band and the characteristic of the human ear's unequal resolution at different frequency bands. In this paper, we present a new wavelet linear prediction subband coding algorithm (WLPSC), by employing a wavelet filter bank based on the auditory model. We divide the input speech signal into four subbands, and then code each subband respectively. Experimental results show that this algorithm can greatly reduce the hoarse output of vocoders.