| 摘要 |
A data compressor codes each frame of a digital input signal with both equal length coding and unequal length coding and selects the coding requiring fewer bits to code the frame as a frame of the compressed digital signal provided by the data compressor. Also included in the compressed digital signal is a decision signal that indicates the coding of the frame. In a variation, the input signal is divided in frequency into plural frequency ranges and a frequency range signal in each frequency range is coded with both equal length coding and unequal length coding. For each frequency range, the coding requiring fewer bits to code each frame of the frequency range signal is selected and included in the compressed digital signal. A decision signal for each frequency range is included in the compressed digital signal. A complementary data expander extracts the decision signal from the compressed digital signal. The expander expands each frame in the compressed digital signal using equal length decoding or unequal length decoding selected according to the extracted decision signal. In a variation, a decision signal is extracted for each frequency range, and each coded frequency range signal is expanded using equal length decoding or unequal length decoding selected according to the extracted decision signal for the frequency range.
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