Abstract: Various methods and systems disclosed compand audio signals using signal prediction, followed by expansion and reconstruction. The methods and systems compress and expand an error signal that represents deviations between samples of the original signal and predicted samples. Each predicted sample is generated by an extrapolation based on a sub-sequence of prior samples of the original signal. A time series of correction samples based on the error signal as it is received from the analog channel after amplitude expansion. Output samples are then generated from the sums of the correction samples and respective predicted samples of a second time series, each of which is extrapolated based on a sub-sequence of prior correction samples. Numerous variations are also disclosed.

Abstract: A text-to-speech synthesizer employs database that includes units. For each unit there is a collection of unit selection parameters and a plurality of frames. Each frame has a set of model parameters derived from a base speech frame, and a speech frame synthesized from the frame's model parameters. A text to be synthesized is converted to a sequence of desired unit features sets, and for each such set the database is perused to retrieve a best-matching unit. An assessment is made whether modifications to the frames are needed, because of discontinuities in the model parameters at unit boundaries, or because of differences between the desired and selected unit features. When modifications are necessary, the model parameters of frames that need to be altered are modified, and new frames are synthesized from the modified model parameters and concatenated to the output. Otherwise, the speech frames previously stored in the database are retrieved and concatenated to the output.

Abstract: A method factors a functional (i.e., ambiguous) finite state transducer (FST) into a bimachine with a reduced intermediate alphabet. Initially, the method determines an emission matrix corresponding to a factorization of the functional FST. Subsequently, the emission matrix is split into a plurality of emission sub-matrices equal in number to the number of input symbols to reduce the intermediate alphabet. Equal rows of each emission sub-matrix are assigned an identical index value in its corresponding factorization matrix before creating the bimachine.