An improved mixed excitation linear prediction (MELP) coder

Unno, T.; Barnwell, T.P.; Truong, K.K.

doi:10.1109/icassp.1999.758108

Cited by 19 publications

(18 citation statements)

References 4 publications

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“…Pitch estimation algorithms are responsible for computation of the pitch period and classification of voiced and unvoiced frames. For this reason, we have chosen a strategy based upon the pitch detection algorithm introduced by Unno et al [7], which uses a sliding window to further reduce incorrect pitch values and voicing decisions. The deployment of a sliding window can reduce the artificial noise usually found in non-stationary segments that contain vowels and result in more accurate voicing decisions and pitch estimates.…”

Section: Pitch Detectionmentioning

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%

“…Pitch detectors are responsible for the computation of the pitch period as well as for the classification of voiced and unvoices frames. In the encoding scheme described in this paper, we have chosen a strategy based on the pitch detection algorithm reported in [7], that uses a sliding window to further reduce incorrect pitch values and voicing decisions. We also employ a classification algorithm that distinguishes voiced, unvoiced fricatives, unvoiced stops and silence frames.…”

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: Pitch Detectionmentioning

confidence: 99%

Section: Fricatives and Stops Encodingmentioning

confidence: 99%

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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“…For the detection of stop sounds we employ the peakiness value of the LPC residual signal r(n) and a sliding window is used to find the frame position that maximizes the peakiness value [6]. The peakiness value with the sliding window is given by wh P = re N is the frame size, and T, is the m rtimum sliding range that is also used in (1).…”

Section: Detection Of Fricatives and Stopsmentioning

confidence: 99%

“…However, the mixed noise and pulse excitation is not capable of reproducing specific signals such as those seen in stops and fricatives. In order to provide a clearer speech quality for the sentences containing stop and fricative sounds, we use an strategy based upon the algorithms introduced by Unno et al [6] and Ehnert 171. It envolves the detection and the modelling and synthesis of these signals.…”

Section: Sound Specific Encodingmentioning

confidence: 99%

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

Lamare

Silva²,

Alcaim³

2002 IEEE International Symposium on Circuits and Systems. Proceedings (Cat. No.02CH37353)

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In this paper we investigate the use of fricatives and stops modelling and synthesis techniques with a spectral envelope reconstruction combined with noise reduction postfilter (SERNR) in mixed voiced-unvoiced multiband excitation coders. We perform a comparative analysis amongst a noise excitation approach operating at 1.75 kbls and a fricatives and stops excitation technique operating at 0.4 kb/s. A novel SERNR postfiltering technique that significantly enhances the decoded speech is proposed and compared with the well-known adaptive spectral enhancement (ASE) filter.

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Low-Bit-Rate Speech Coding

McCree

2008

Springer Handbook of Speech Processing

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An improved mixed excitation linear prediction (MELP) coder

Cited by 19 publications

References 4 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

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

Low-Bit-Rate Speech Coding

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