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.

Successive orthogonalizations in the multistage CELP coder

Abstract: The authors investigate three algorithms that orthogonalize codebooks in a multi-stage code excited linear prediction (CELP) speech coder. They carry out the same processing, a locally optimal modeling of the perceptual signal, but the computational costs differ. The authors show that the recursive modified Gram-Schmidt algorithm extra computational cost is less than the other two. An orthogonal codebook is defined a priori and the authors observe an equivalence to orthogonal transform coding. Three methods based on the Karhunen-Loeve transform for designing this codebook are compared. A partitioned shape-gain VQ is applied in the transform domain. >

Voiced speech coding at very low bit rates based on forward-backward waveform prediction

Abstract: Techniques for coding voiced speech at very low bit rates are investigated and a new algorithm, designed to produce high quality speech with low complexity, is proposed. This algorithm encodes and transmits partial representative waveforms (RWs) from which the complete speech waveforms are reconstructed by using a method called forward-backward waveform prediction (FBWP). The RW is encoded at 20-30 ms intervals with a low complexity approach, taking into account the special initial conditions of short- and long-term filters. The basic idea of FBWP is essentially consistent with that of the prototype waveform interpolation (PWI) algorithm, which was reported to be capable of producing high-quality voiced speech at a bit rate of between 3.0 and 4.0 kb/s. By implementing the FBWP in the time domain, fast computation is thereby made possible while high-quality speech can be obtained at bit rate of about 3 kb/s. As in the PWI method, the proposed algorithm may be combined with an LP-based speech coder which uses a noise-like excitation to reproduce unvoiced speech. >

A long history quantization approach to scalar and vector quantization of LSP coefficients

Abstract: LHQ (long history quantization), when applied in conjunction with scalar quantization for the coding of LSP (line spectrum pair) coefficients in a CELP (code excited linear prediction) system, offers transparent quantization at an average bit rate of 25 bits/frame. Certain improvements to the LHQ-scalar quantization scheme are presented which further reduce the average LSP bit rate to about 22 bits/frame. In addition, a novel LHQ-vector quantization scheme is proposed, which allows the transparent quantization of LPC coefficients with only 19 bits/analysis frame. >

Speech encoding device, speech decoding device, speech signal transmitting method, and program

Abstract: PROBLEM TO BE SOLVED: To suppress propagation of quality deterioration of a decoded speech signal due to frame disappearance in a communication system using a CELP type speech encoding device. SOLUTION: The speech encoding device detects pitch peak position information of a speech signal and transmits the pitch peak position information to a speech decoding device together with the encoded speech signal and then if the speech signal has a lost frame, the speech decoding device can compensate quality deterioration due to the lost frame according to the pitch peak position information. COPYRIGHT: (C)2004,JPO

Wideband speech coding in 7.2 kbit/s

Abstract: A novel method for coding wideband speech at medium bit rates is proposed. A subband approach is adopted, using sharp cut-off filters to split the speech into lower and upper bands. This allows the upper-band to be very coarsely quantized without introducing significant distortion at low frequencies in the reconstructed speech, which would normally occur using short QMF (quadrature mirror filter). A standard CELP (code excited linear prediction) coder is used for the low-frequency band, and the upper band is quantized using a second-order predictor and gain shape vector quantization at 0.05 bit sample, yielding an overall bit rate of 7.2 kbit/s. The overall effect is to produce a wideband coder that has almost the same computational requirements as a narrowband CELP coder and only a slight increase in the bit rate. >