Switched multiple sequence excitation model for low bit rate speech compression
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United States of America Patent
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Aug 25, 1998
Grant Date -
N/A
app pub date -
Jul 1, 1996
filing date -
Jul 1, 1996
priority date (Note) -
Expired
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Abstract
An apparatus for compressing a speech signal into a compressed speech signal that is represented by a plurality of parameters. A time-varying digital filter is used to model the vocal tract. A number of LPC coefficients specify the transfer function of the filter updated on frame basis. An excitation signal is input to the filter analyzed on sub frame basis. This excitation signal includes either an adaptive vector quantiser code or a first pulse sequence, followed by a second pulse sequence. Selection logic is used to determine whether the adaptive vector quantiser code or the first pulse sequence better represents the speech signal. Based thereon, a switch selects either the adaptive vector quantiser code or the first pulse sequence. Thus, the parameters which are transmitted through a channel to a destination decoder include the LPC filter coefficients, either the adaptive vector quantiser code or the first pulse sequence, the second pulse sequence, and one bit indicating the state of the switch.
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