Sound specific modelling and synthesis with a new postfiltering in low bit rate speech coding

Lamare, Rodrigo C. de; Silva, L.M. da; Alcaim, Abraham

doi:10.1109/iscas.2002.1010356

Cited by 3 publications

(14 citation statements)

References 5 publications

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“…The noise excitation usually employed to model unvoiced sounds is not capable of adequately representing unvoiced stops and fricatives. In order to provide a clearer speech quality for the sentences containing stops and fricatives sounds, we use a strategy based upon the algorithms recently introduced in [9].…”

Section: Fricatives and Stops Encodingmentioning

confidence: 99%

“…The methods reported in [9] resemble those introduced in [7] and [8]. However, the overall scheme has novel contributions with respect to some specific points that differ from the techniques described in [7] and [8].…”

Section: Fricatives and Stops Encodingmentioning

confidence: 99%

“…This method requires no transmission of LPC parameters, however, according to informal listening tests it has shown inferior performance to Unno et al's. In [9] we proposed a modification of the techniques introduced by Unno et al to encode stops that rather than transmitting LSF vectors, makes use of pre-stored templates of LPC coefficients. Informal listening tests have shown that our approach is capable of reproducing speech at a quality comparable to that delivered by the method in [7], while reducing the bit rate to only 0:4 kb=s and offering an attractive trade-off between speech quality and bit rate.…”

Section: Fricatives and Stops Encodingmentioning

confidence: 99%

“…The SER approach has been shown to reproduce speech with a quality comparable to the ASE technique. Here, we describe a spectral envelope reconstruction combined with noise reduction (SERNR) postfilter [9], that combines the strengths of the ASE and the SER strategies. The SERNR postfilter has the spectral envelope restoration properties of the SER filter and the noise reduction capabilities of the ASE technique.…”

Section: Introductionmentioning

confidence: 99%

“…The SERNR postfilter has the spectral envelope restoration properties of the SER filter and the noise reduction capabilities of the ASE technique. The SERNR can significantly enhance decoded speech quality and has shown a performance superior to the traditional ASE filter for MMBE platforms [9,23]. To reduce background noise and enhance the quality of the synthesised speech, we employ a noise suppression method, proposed by Arslan et al [24], that is based on a smooth spectral subtraction of noise-corrupted speech.…”

Section: Introductionmentioning

confidence: 99%

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Strategies to improve the performance of very low bit rate speech coders and application to a variable rate 1.2 kb/s codec

Lamare

Alcaim

2005

IEE Proc., Vis. Image Process.

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This paper presents several strategies to improve the performance of very low bit rate speech coders and describes a speech codec that incorporates these strategies and operates at an average bit rate of 1.2 kb/s. The encoding algorithm is based on several improvements in a mixed multiband excitation (MMBE) linear predictive coding (LPC) structure. A switched-predictive vector quantiser technique that outperforms previously reported schemes is adopted to encode the LSF parameters. Spectral and sound specific low rate models are used in order to achieve high quality speech at low rates. An MMBE approach with three sub-bands is employed to encode voiced frames, while fricatives and stops modelling and synthesis techniques are used for unvoiced frames. This strategy is shown to provide good quality synthesised speech, at a bit rate of only 0.4 kb/s for unvoiced frames. To reduce coding noise and improve decoded speech, spectral envelope restoration combined with noise reduction (SERNR) postfilter is used. The contributions of the techniques described in this paper are separately assessed and then combined in the design of a low bit rate codec that is evaluated against the North American Mixed Excitation Linear Prediction (MELP) coder. The performance assessment is carried out in terms of the spectral distortion of LSF quantisation, mean opinion score (MOS), A/B comparison tests and the ITU-T P.862 perceptual evaluation of speech quality (PESQ) standard. Assessment results show that the improved methods for LSF quantisation, sound specific modelling and synthesis and the new postfiltering approach can significantly outperform previously reported techniques. Further results also indicate that a system combining the proposed improvements and operating at 1.2 kb/s, is comparable (slightly outperforming) a MELP coder operating at 2.4 kb/s. For tandem connection situations, the proposed system is clearly superior to the MELP coder. R.C. de Lamare and A.

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Section: Fricatives and Stops Encodingmentioning

confidence: 99%

Section: Fricatives and Stops Encodingmentioning

confidence: 99%

Section: Fricatives and Stops Encodingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Strategies to improve the performance of very low bit rate speech coders and application to a variable rate 1.2 kb/s codec

Lamare

Alcaim

2005

IEE Proc., Vis. Image Process.

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Analysis of Postfilters for Low Bit Rate Speech Coders in Tandem Connections

Lamare¹,

Alcaim²

2002

Anais Do 2002 International Telecommunications Symposium

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In this paper we analyse postfiltering techniques for very low bit rate speech coders in tandem connections. A mixed multiband excitation (MMBE) linear predictive coding (LPC) algorithm, that encodes voiced frames at 1.75 kb/s and unvoiced frames at 0.4 kb/s, is employed to assess the performance of different postfilters in tandem connections. We perform a comparative analysis of the well known adaptive spectral enhancement (ASE) technique with a recently reported approach, called spectral envelope restoration combined with noise reduction (SERNR) postfilter, using the same MMBE platform. Subjective listening tests in tandem connections show that the SERNR technique is clearly superior to the ASE postfilter.

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Impacto da Quantização das LSF sobre a Qualidade de Voz em Codecs a Baixas Taxas Operando em Redes IP

Berkowicz¹,

Lamare²,

Alcaim.³

2004

Anais Do XXI Simpósio Brasileiro De Telecomunicações

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Resumo-Este artigo examina o impacto da quantizac ¸ão vetorial das LSFs sobre a qualidade de voz em codecs a baixas taxas operando em redes IP. São considerados diferentes esquemas de quantizac ¸ão vetorial (QV) multiestágio com busca em árvore envolvendo QV sem memória e QV preditiva chaveada com 2 e 4 classes. A distribuic ¸ão de perda de quadros em redes IP foi modelada de acordo com o Modelo de Gilbert e a avaliac ¸ão de desempenho foi realizada tanto em termos das distorc ¸ões espectrais como da qualidade de voz resultante de codecs a baixas taxas. Esta última foi medida através da recomendac ¸ão ITU-T P.862 de avaliac ¸ão perceptiva de qualidade da voz (PESQ), além de testes de escuta informais.Palavras-Chave-Quantizadores vetoriais multiestágio, redes IP, perda de quadros, avaliac ¸ão perceptiva de qualidade da voz (PESQ) .

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Sound specific modelling and synthesis with a new postfiltering in low bit rate speech coding

Cited by 3 publications

References 5 publications

Strategies to improve the performance of very low bit rate speech coders and application to a variable rate 1.2 kb/s codec

Strategies to improve the performance of very low bit rate speech coders and application to a variable rate 1.2 kb/s codec

Analysis of Postfilters for Low Bit Rate Speech Coders in Tandem Connections

Impacto da Quantização das LSF sobre a Qualidade de Voz em Codecs a Baixas Taxas Operando em Redes IP

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