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.

A Fast Pitch Searching Algorithm Using Correlation Characteristics in CELP Vocoder

Abstract: The major drawback to the Code Excited Linear Prediction(CELP) type vocoders is their large computational requirements. In this paper, a simple method is proposed to reduce the pitch searching time in the pitch filter almost without degradation of quality. Bease upon the observational regularity of the correlation function of speech, the searching range can be restricted to the positive side in pitch search. This is done by skipping the negative side with the width which is estimated from the previous positive envelope. In addition to that, the maximum number of available lags can be limited by the threshold, , which is set on 58 empirically. So, only the limited numbers of lags are considered in pitch search, which is less than a half of that of the full search method. By using the proposed method in pitch search, its required computations are greatly reduced. Experimental result shows 51% time reduction almost without lowering the speech quality in segmental SNR measure.

Voice coding device

Abstract: PURPOSE:To provide a voice coding device in which low bit rate processing and voice signal processing are realized on a piece of DSP. CONSTITUTION:The coder of the device is provided with a TC input buffer 1 which stores voice input signals, a counter section 2 which counts the number of data, a TC processing section 3 which detects a pitch period when the counted value exceeds a prescribed threshold and executes time axis compression to the detected pitch period to be the half period, a CELP-I/F buffer 4 which stores the time axis compressed data, a CELP coding processing section 5 which selects a coding book in which the difference between the voice obtd. by subjecting the data concerned to vector processing and the composed voice becomes a minimum and conducts a voice compression and a CELP output buffer 6 which temporarily stores the processed data.

Interaction of speech disorders with speech coders: effects on speech intelligibility

Abstract: Modern speech coding schemes have been developed to address the demand for economical spoken language telecommunication of acceptable quality. A variety of speech coding algorithms have been described, which compress speech to facilitate efficient transmission of spoken language over communication networks ((J.R. Deller Jr., 1993; P.E. Papamichalis, 1987). Most such speech coding algorithms are lossy in the sense that the processed speech is not identical to the original speech. As a result, some distortion is invariably introduced with any lossy speech coding strategy. For this reason, candidate coders undergo detailed evaluation to ensure that the associated speech output is of acceptable quality (S.R. Quackenbush et al., 1988). Three different coding algorithms were investigated relative to unprocessed speech: the Codebook Excited Linear Prediction (CELP), the Global System for Mobile Communications (GSM) algorithm which is a standardized speech coding algorithm in Europe, and the Linear Predictive Coding (LPC) algorithm. The specific coding schemes evaluated were MatLab implementations of NSA FS-1015 LPC-l0e; NSA FS-1016 CELP-v3.2; and ETSI GSM (A. Spanias, 1995). One of the goals of this study was to quantify the coding distortion using objective measures and to correlate these measures with speech intelligibility and subjective quality data, in the hope of identifying one or more measures that can predict the subjective results.

Understanding the quality losses of embedded speech and audio coders

Abstract: At a given bitrate, and for a given coding structure, an embedded speech coder often shows a loss in quality when compared to a corresponding non-embedded coder. This paper presents a general framework to investigate how this loss depends on common design choices such as the frame length, prediction order and quantizer dimensions used by the coders. The results show that predictive and transform predictive coding schemes, and schemes which normalize energy over short intervals in time and frequency, may see smaller losses when used in embedded designs than compared to other coding paradigms.

Integration of a CELP coder in the ARDOR universal sound codec.

Abstract: This paper describes the CELP coding module within the Adaptive Rate-Distortion Optimized sound codeR (ARDOR). The ARDOR codec combines coding techniques of different nature using a rate-distortion control mechanism, and is able to adapt to a large range of signal characteristics and system constraints. The implemented CELP codec is derived from the 3GPP AMR-WB codec. Adaptations were necessary to match the ARDOR structure constraints and several new features have been added to improve the codec performance in this context. Listening test results are given to illustrate the behavior of the final codec compared to state-of-the-art coders.