Method of coding voice signals and device using said method

• US 4,569,075 A
• Filed: 07/19/1982
• Issued: 02/04/1986
• Est. Priority Date: 07/28/1981
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Nussbaumer, Henri
• Primary Examiner(s): Kemeny, E. S. Matt
• Application Number:
  US06/399,385
• Time in Patent Office: 1,296 Days
• Field of Search: 381/29, 381/30, 381/31, 381/32, 381/33, 381/34, 381/35, 381/36, 381/37, 381/38, 381/39
• US Class Current: 704/203
• CPC Class Codes: H04B 1/667 using a division in frequency subbands for TV signals H04N19/63

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 y_i and y_i (with i=1, 2, . . . , N), respectively. The subband components y_i and y_i are combined together to generate information representative of the phase (φ_i) and amplitude (ρ_i) 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.

Claims

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, and

low-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.