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.

Medium band speech coding for mobile radio communications

Abstract: The authors propose a low cost 6 kbps multipulse-excited linear prediction coder for 8 kbps transmissions on 12.5 kHz radio channels. The main purpose of this system is to give good intelligibility and good speaker recognition. Against transmission errors, the authors present a correcting strategy and an extrapolation method that hides lost speech frames. >

Scalable wideband speech coding using G.729 as a component

Abstract: This paper proposes a scalable band-split wideband speech coding system that uses G.729 as a component and can decode speech from even part of the 16 kbitss encoded data. The configuration of the proposed scalable encoding is as follows. The 7-kHz band speech signal is split into lower and upper bands, which are encoded separately. The lower band is scalably encoded at 12 kbitss, and the upper band is encoded by CELP composed only of the noise codebook (4 kbitss). In the lower band, the lower-level encoder (core layer) is included in the upper-level encoder (enhancement layer) as part of the functional element, to improve the performance of the whole lower-band encoder. To further improve quality while retaining scalability to the core coder, an additional pitch prediction scheme is proposed in which the excitation component of the enhancement layer is used in the pitch component. Performance evaluation by objective measures and a subjective evaluation experiment for the proposed schemes, showed that the quality is greatly improved compared with the conventional method. © 2005 Wiley Periodicals, Inc. Syst Comp Jpn, 36(3): 65–74, 2005; Published online in Wiley InterScience (). DOI 10.1002sscj.10555

Transcoder for speech codecs of different CELP type and method therefor

Abstract: A transcoder for use between speech codecs using different Code-Excited Linear Prediction (CELP) type and a method therefor are disclosed. The transcoder includes a decoding unit of an input CELP codec, a transcoding filter, a transcoding filter design unit, and an encoding unit of an output CELP codec. By substituting a post-filter and a perceptual weighting filter of a prior art with one transcoding filter, the calculation amount of the transcoder is reduced, and speech quality decoded at a receiving end is improved.

A high quality voice coder with integrated echo canceller and voice activity detector for mobile satellite applications

Abstract: In the last decade, low bit rate speech coding research has received much attention resulting in newly developed, good quality, speech coders operating at as low as 4.8 Kb/s. Although speech quality at around 8 Kb/s is acceptable for a wide variety of applications, at 4.8 Kb/s more improvements in quality are necessary to make it acceptable to the majority of applications and users. In addition to the required low bit rate with acceptable speech quality, other facilities such as integrated digital echo cancellation and voice activity detection are now becoming necessary to provide a cost effective and compact solution. In this paper we describe a CELP speech coder with integrated echo canceller and a voice activity detector all of which have been implemented on a single DSP32C with 32 KBytes of SRAM. The quality of CELP coded speech has been improved significantly by a new codebook implementation which also simplifies the encoder/decoder complexity making room for the integration of a 64-tap echo canceller together with a voice activity detector.

Performance evaluation of Code Excited Linear Prediction Speech Coders at various bit rates

Abstract: Attractive improvements have been made during these days in coding speech with high quality at low bit rates and low delay. The need for low bit rate speech coding algorithms continues, supported by the ever increasing number of users to the wireless communication networks. This paper discusses the implementation details of Code Excited Linear Prediction Speech Coder at different bit rates (16Kbps, 9.6Kbps, 7Kbps, 6.8Kbps, 4.9Kbps and 4.8Kbps) and analytical evaluation of performance in terms of bit rate and quality using PRAAT software.