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Two-channel analysis-by-synthesis linear predictive speech coder
2000 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

This master thesis is about a two-channel speech coder belonging to the CELP family. A potential application for a two-channel speech coder is teleconferencing. The background of the coder is discussed in terms of expected user scenarios and what differences one can find in the resulting two-channel speech signals as compared to speech signals in traditional telephony situations. Then the physical model on which CELP coders are based is introduced and the expressions controlling the operation of a single-channel CELP coder are derived. A design for a two-channel CELP coder was provided as background material for this master thesis. This design is explored and its controlling expressions are deriveved in a way that parallels the single-channel case. The design was implemented and with the help of this implementation, the two-channel CELP design is evaluated. Three concepts within the two-channel CELP design were expected to reduce the bit-rate to less than twice that of a corresponding single-channel CELP: • The introduction of a cross-channel predictor in the short-term predictor. • A long term cross-channel prediction unit. • Quantization and/or prediction of parameters for the two channels. The first idea did not result in any performance improvements. The second idea showed some promise. The examination of parameter correlation for the two channels indicated that quantization/prediction indeed would be efficient. Apart from this, it was found that an algebraic codebook structure, which adaptively allocates pulses within the two channels, could be used. These results are used in the final chapter of the report where the design of a different two-channel CELP coder is outlined.

Place, publisher, year, edition, pages
Keyword [en]
Technology, speech coding, CELP, GSM, audio, multi channel stereo coder, codec
Keyword [sv]
URN: urn:nbn:se:ltu:diva-58511ISRN: LTU-EX--00/281--SELocal ID: f184ce14-18b2-434b-a6a4-a1e6a9a4481eOAI: diva2:1031899
Subject / course
Student thesis, at least 30 credits
Educational program
Computer Science and Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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