Improving the performance of the 16 kb/s LD-CELP speech coder

Chen, J.-H.; Jayant, N.; Cox, R.V.

doi:10.1109/icassp.1992.225970

Cited by 15 publications

(3 citation statements)

References 5 publications

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“…There are a couple of reasons for that but the main reason can be explained by postfiltering. The postfilters of the current standards are generally tuned for a single encoding; thus the amount of filtering becomes excessive in tandem conditions, resulting in distorted speech [7]. 4 shows a block diagram of the proposed LSP domain method.…”

Section: A Lsp Mapping Methodsmentioning

confidence: 99%

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Improving the transcoding capability of speech coders

Kang

Kim

Cox

2003

IEEE Trans. Multimedia

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With the trend of merging various communication networks, a need arises to provide transcoding between different speech coding formats. Presently this means cross tandeming the two coders in each case. This results in both quality loss and extra delay. A possible alternative is using a bitstream mapping approach that directly converts parameter values. For several standard coders having a similar coding structure, it should be possible to generate comparable or better quality without adding much delay or complexity. This paper proposes a bitstream mapping method between ITU-T Recommendation G.729 and TIA IS-641. Informal listening tests and the perceptual subjective quality measure (PSQM) scores show that the proposed method has better quality than the cross tandeming method, while it has at least 5 ms less delay and six times less computation.

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Section: A Lsp Mapping Methodsmentioning

confidence: 99%

“…A simple solution to operate the different speech coding standards together is using a cross tandeming (or transcoding) method: generate a speech signal by using a decoder from one standard and then re-encode the signal with the other standard [6], [7]. From this point on, this approach is referred to as a conventional cross tandeming.…”

Section: Introductionmentioning

confidence: 99%

Improving the transcoding capability of speech coders

Kang

Kim

Cox

2003

IEEE Trans. Multimedia

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“…The quality of speech synthesized in this manner is often judged as unnatural due to incorrect voicing decisions, poor spectral resolution, and oversimplified excitation functions (Wong, 1980;Kahn and Garst, 1983). A number of approaches have been taken to improve the excitation waveform for LP by modeling the residue or the glottal waveform characteristics (Bergstrom and Hedelin, 1989;Caspers and Atal, 1987;Chen et al, 1992;Childers and Wu, 1990;Dankberg and Wong, 1979;Griffin and Lim, 1988;Haagen et al, 1992;Hedelin, 1986Hedelin, , 1988Kang and Everett, 1985 can further improve LP synthesis, since early work showed that the glottal pulse shape was important for synthesizing natural sounding vowels (Rosenberg, 1971;Holmes, 1973). Furthermore, recent research has shown that characteristics of the glottal source waveform, such as the glottal pulse width, glottal pulse skewness, the abruptness of glottal closure, and a turbulence noise component (Childers and Lee, 1991), are important both for speech synthesis and for modeling voice types and vocal disorders (Carlson et al, 1991;Childers and Ahn, 1994;Childers et al, 1989b;Wu, 1990, 1991;Childers and Lee, 1991;Childers and Wong, 1994;Fant, 1993;Fant et al, 1985;Fant and Lin, 1988;Fujisaki and Ljungqvist, 1986;Klatt and Klatt, 1990; Karlsson, 1986Karlsson, , 1988Karlsson, , 1990Karlsson, , 1991Karlsson, , 1992Milenkovic, 1993;Pinto et al, 1989).…”

Section: Introductionmentioning

confidence: 99%

Speech synthesis by glottal excited linear prediction

Childers

1994

The Journal of the Acoustical Society of America

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This paper describes a linear predictive (LP) speech synthesis procedure that resynthesizes speech using a 6th-order polynomial waveform to model the glottal excitation. The coefficients of the polynomial model form a vector that represents the glottal excitation waveform for one pitch period. A glottal excitation code book with 32 entries for voiced excitation is designed and trained using two sentences spoken by different speakers. The purpose for using this approach is to demonstrate that quantization of the glottal excitation waveform does not significantly degrade the quality of speech synthesized with a glottal excitation linear predictive (GELP) synthesizer. This implementation of the LP synthesizer is patterned after both a pitch-excited LP speech synthesizer and a code excited linear predictive (CELP) speech coder. In addition to the glottal excitation codebook, we use a stochastic codebook with 256 entries for unvoiced noise excitation. Analysis techniques are described for constructing both codebooks. The GELP synthesizer, which resynthesizes speech with high quality, provides the speech scientist a simple speech synthesis procedure that uses established analysis techniques, that is able to reproduce all speed sounds, and yet also has an excitation model waveform that is related to the derivative of the glottal flow and the integral of the residue. It is conjectured that the glottal excitation codebook approach could provide a mechanism for quantitatively comparing the differences in glottal excitation codebooks for male and female speakers and for speakers with vocal disorders and for speakers with different voice types such as breathy and vocal fry voices. Conceivably, one could also convert the voice of a speaker with one voice type, e.g., breathy, to the voice of a speaker with another voice type, e.g., vocal fry, by synthesizing speech using the vocal tract LP parameters for the speaker with the breathy voice excited by the glottal excitation codebook trained for vocal fry.

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8 kb/s Low-Delay CELP Coding of Speech

Chen

Rauchwerk

1993

Speech and Audio Coding for Wireless and Network Applications

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Improving the performance of the 16 kb/s LD-CELP speech coder

Cited by 15 publications

References 5 publications

Improving the transcoding capability of speech coders

Improving the transcoding capability of speech coders

Speech synthesis by glottal excited linear prediction

8 kb/s Low-Delay CELP Coding of Speech

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