Patent Document ID: 6061648
Application ID: 09030910

Base Claim:
1. An apparatus for coding a speech signal, comprising: an input device that inputs a mixed speech signal of a plurality of speakers; a separating device that analyzes period characteristics of the input mixed speech signal entered by said input device, and separates the input mixed speech signal into a plurality of single speech signals each associated with a corresponding one of the plurality of speakers, based on a result of the analysis; a first extracting device that extracts source speech characteristic parameters included in each of the single speech signals derived by said separating device, said source speech characteristic parameters representing characteristics of source speech generated from vocal cords of each of the speakers; a second extracting device that extracts a generic vocal-tract characteristic parameter from the input mixed speech signal, said generic vocal-tract characteristic parameter representing a vocal-tract characteristic shared by the plurality of speakers; and an output device that outputs the source speech characteristic parameters extracted by said first extracting device, and the vocal-tract characteristic parameter extracted by said second extracting device.

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Claim 5:
5. An apparatus as claimed in claim 1, further comprising: a source speech decoder that decodes source speech signals of the respective speakers, based on the source speech characteristic parameters extracted by said first extracting device with respect to the plurality of speakers, respectively, and forms a source speech signal for the plurality of speakers by synthesizing the decoded source speech signals of the respective speakers; a vocal-tract filter that filters the source speech signal for the plurality of speakers formed by said source speed decoder, based on the generic vocal-tract characteristic parameter extracted by said second extracting device, so as to decode a mixed speech signal indicative of mixed speech of the plurality of speakers; an error detector that detects an error between the mixed speech signal decoded by said vocal-tract filter and the input mixed speech signal; wherein said first extracting device extracts one of said source speech characteristic parameters so as to minimize the error detected by said error detector.