A method for lost speech samples
recovery in speech transmission systems is disclosed. The method employs a waveform coder operating on digital speech samples. It exploits the composite model of speech, wherein each speech segment contains both periodic and
colored noise components, and separately estimates these two components of the unreliable samples. First, adaptive FIR filters computed from received
signal statistics are used to interpolate estimates of the periodic component for the unreliable samples. These FIR filters are inherently stable and typically short, since only strongly correlated elements of the
signal corresponding to
pitch offset samples are used to compute the estimate. These periodic estimates are also computed for sample times corresponding to reliable samples adjacent to the unreliable sample interval. The differences between these reliable samples and the corresponding periodic estimates are considered as samples of the
noise component. These samples, computed both before and after the unreliable sample interval, are extrapolated into the time slot of the unreliable samples with
linear prediction techniques. Corresponding periodic and
colored noise estimates are then summed. All required statistics and quantities are computed at the
receiver, eliminating any need for special
processing at the
transmitter. Gaps of significant duration, e.g., in the tens of milliseconds, can be effectively compensated.