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.

Effect of Speech Coding on Recognition of Consonant-Vowel (CV) Units

Abstract: The rapid growth of mobile users is creating great deal of interest in the development of robust speech systems in wireless environment. The major challenges involved in adapting the present speech processing technology to mobile wireless systems are: (1) Effect of varying background conditions in mobile environment. (2) Degradations introduced by the speech coders. (3) Errors introduced due to wireless radio channels. In this paper we analyzed the effect of different low bit rate speech coders on the recognition of Consonant-Vowel (CV) units in Indian languages using monolithic SVM and hybrid HMM-SVM models. Speech coders considered in this work are GSM full rate (ETSI 06.10), CELP (FS-1016), and MELP (TI 2.4kbps). From the results, it is observed that there is a significant effect of coding on the recognition of CV units.

Pyramid CELP: Embedded speech coding for packet communications

Abstract: In this paper we present a novel speech coding algorithm for transmission over packet networks based on CELP (Code-Excited-Linear-Prediction). While various CELP type speech coders like the ITU-T G.729 or the Adaptive Multi-Rate (AMR) codec are applicable to packet voice communication systems such as the Internet, there are some fundamental reasons that may limit their Performance in case of packet loss. We investigate the alternative of embedded coding in the CELP framework. focussing on an efficient quantization of the excitation signal to generate a hierarchically-structured bit stream by means of pyramid coding [1]. Thus, the receiver can reconstruct speech at a basic quality by decoding only a subset of the entire bit stream. The quality of the decoded speech increases with the amount of received bits. We demonstrate the performance by an experimental hierarchical wideband (0.05–7 kHz) speech coder, applied to an IP (Internet Protocol) channel simulation.

Mixed wideband speech and music coding using a speech/music discriminator

Abstract: In multimedia applications such as videoconferencing, users are demanding higher quality speech/audio transmission than the POTS can offer. 7kHz wideband speech/audio offers a good compromise between bandwidth and sound quality. It improves the intelligibility and naturalness of speech and adds a feeling of transparent communication. Currently the only existing international standard for coding such signals is the G.722 wideband speech/audio coder. While its coding quality is satisfactory it leaves much to be desired with its bit rate. The CELP-based approach has been very successful in telephone bandwidth speech coding, but is not suitable for coding non-speech signals because of the assumed signal production model. This paper proposes an alternative approach to mixed speech/music coding, which uses a discriminator to separate music signals from speech, and codes them with the G.722 coder and a G.723.1-based speech coder, respectively. Simulations shows very promising results.

Efficient algorithms for obtaining multipulse excitation for LPC coders

Abstract: Since the presentation of multi-pulse excitation concept for LPC coders, by Atal and Remde, many different analysis techniques have been proposed to derive the excitation waveform. This paper describes several approaches for pulse amplitude and position determination. The original solution is compared to procedures which work directly on the residual signal, or which compute again a jointly optimal set of amplitudes, or which improve the filter parameters by taking into account the computed multi-pulse excitation. In addition, other novel techniques, based on the insertion of a long term pitch predictor in the multi-pulse analysis are presented. Also, the idea of a two stage modelization is introduced. Results of experimental evaluations for typical configurations, with respect to implementation complexity as well as speech quality, are given.

Experiments with a high quality, low complexity 4800 bps residual excited LPC (RELP) vocoder

Abstract: The authors present an approach for achieving high quality speech coding at 4800 bps using a residual excited LPC (RELP) coder. Numerous experiments were performed to identify and code the significant parameters in the spectral, pitch, and residual models. Major principles for high quality residual coding are discussed. >