In a method of transmitting a signal wherein the signal is partitioned into windows comprised of overlapping blocks with each block containing a partial signal. The partial signal in each block is converted into a digital signal and individually coded with a selected window function f(n). The overlapping areas of the window functions are weighted such that the resultant of the overlapping functions in each block equals one. The coded signals are transmitted. The received signals are reconverted into partial analog signals. The window functions are selected in accordance with frequency changes in the original signal.
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1. In apparatus of the type for encoding a signal by means of spectral analysis of overlapping time segments of such signal, and including apparatus for processing respective said time segments according to a window function for imparting a characteristic amplitude function to said respective time segments prior to such analysis of said signal, an improvement comprising:
- means for detecting occurrences of instantaneous frequency changes in said signal exceeding a predetermined frequency change, and generating control signals indicating occurrences of said frequency changes; and
- means, responsive to said control signals, for adaptively providing said window functions such that respective time segments of signal which exhibit said instantaneous frequency changes are subjected to a significantly narrowed window function relative to window functions applied to time segments of signal which do not exhibit said instantaneous frequency changes, and wherein window functions of overlapping time segments overlap.
2. The apparatus set forth in claim 1 wherein said means for providing window functions provides adjacent said window function which are overlapping, with overlapped areas of adjacent window functions being complementary versions of each other.
3. The apparatus set forth in claim 1 further including means for detecting occurrences of amplitude changes in said signal exceeding a predetermined amplitude change, and generating said control signals indicating occurrences of said frequency changes and said amplitude changes.
4. The apparatus set forth in claim 1 further including:
- means for spectrally analyzing said time segments after application of said window functions to generate compressed signal components; and
- means for combining said compressed signal components and signal representing said control signals for transmission.