Method of coding voice signals and device using said method
First Claim
1. A coding device for coding a low frequency band limited portion of a voice signal, said coding device including:
- sampling means for sampling the band limited voice signal fed thereto at its Nyquist frequency (fs) to generate a decimated series of samples;
complex filtering means connected to said sampling means for deriving therefrom for each sample of said decimated series of samples a couple of signal components in quadrature with each other, said complex filtering means comprising;
first and second modulation means alternatively connected to said sampling means for multiplying said couple of signal components by the cyclic sequence (1, 0, -1,
0) and (0, 1, 0, -1), respectively, andlow-pass filter means connected to said modulation means, said low-pass filtering means deriving therefrom said couple of signal components in quadrature with each other;
filtering means connected to said complex filtering means for splitting the frequency spectrum of said couple of signal components in quadrature with each other into a given number of subbands through the use of Quadrature Mirror Filter techniques;
phase-amplitude means connected to said filtering means to derive from the contents of each of said subbands a phase information and an amplitude information;
and coding means connected to said phase-amplitude means for coding said phase information and said amplitude information within each of said subbands.
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Accused Products
Abstract
The baseband portion x(t) of a voice signal is first applied to a complex filter which provides a couple of signal components y and y in quadrature with each other. Each of the components y and y is then fed to a bank of QMF filters which split the spectra of y and y into N subbands providing subband components yi and yi (with i=1, 2, . . . , N), respectively. The subband components yi and yi are combined together to generate information representative of the phase (φi) and amplitude (ρi) of the contents of each subband, which information is then transcoded by a coder which dynamically distributes the available bit resources to the various subbands.
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Citations
1 Claim
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1. A coding device for coding a low frequency band limited portion of a voice signal, said coding device including:
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sampling means for sampling the band limited voice signal fed thereto at its Nyquist frequency (fs) to generate a decimated series of samples; complex filtering means connected to said sampling means for deriving therefrom for each sample of said decimated series of samples a couple of signal components in quadrature with each other, said complex filtering means comprising; first and second modulation means alternatively connected to said sampling means for multiplying said couple of signal components by the cyclic sequence (1, 0, -1,
0) and (0, 1, 0, -1), respectively, andlow-pass filter means connected to said modulation means, said low-pass filtering means deriving therefrom said couple of signal components in quadrature with each other; filtering means connected to said complex filtering means for splitting the frequency spectrum of said couple of signal components in quadrature with each other into a given number of subbands through the use of Quadrature Mirror Filter techniques; phase-amplitude means connected to said filtering means to derive from the contents of each of said subbands a phase information and an amplitude information; and coding means connected to said phase-amplitude means for coding said phase information and said amplitude information within each of said subbands.
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Specification