Forward time-domain aliasing cancellation using linear-predictive filtering to cancel time reversed and zero input responses of adjacent frames

摘要

In a coder, a method for producing forward aliasing cancellation (FAC) parameters for cancelling time-domain aliasing caused to a coded audio signal in a first transform-coded frame by a transition between the first transform-coded frame using a first coding mode with overlapping window and a second frame using a second coding mode with non-overlapping window, comprising: calculating a FAC target representative of a difference between the audio signal of the first frame prior to coding and a sum of synthesis of the coded audio signal of the first transform-coded frame and a time reversed version of last synthesis samples of the second frame as well as a zero point response of a synthesis filter used in the second frame; and weighting the FAC target to produce the FAC parameters. In a decoder, weighted forward aliasing cancellation (FAC) parameters are received and inverse weighted to produce a FAC synthesis. Upon synthesis of the coded audio signal in the first frame, the time-domain aliasing is cancelled from the audio signal synthesis using the FAC synthesis.

主权项

1. A method for producing forward aliasing cancellation (FAC) parameters for cancelling time-domain aliasing caused to a coded audio signal in a first transform-coded frame by a transition between the first transform-coded frame using a first coding mode with overlapping window and a second frame using a second coding mode with non-overlapping window, wherein the second frame precedes the first frame, comprising:
calculating, in a coder, a FAC target representative of a difference between (a) the audio signal of the first frame prior to coding and (b) a sum of: a synthesis of the coded audio signal of the first transform-coded frame containing a folding effect formed by a windowed and folded portion of a synthesis of the coded audio signal in the second frame subtracted from or added to the synthesis of the first frame, a windowed and time-reversed version of last synthesis samples of the second frame, and a windowed zero-input response of a synthesis filter used in the second frame; and weighting, in the coder, the FAC target to produce the FAC parameters, the FAC parameters forming additional information for transmission from the coder to a decoder and for use by the decoder as a basis in canceling the time-domain aliasing in the synthesis of the coded audio signal at the transition between the first transform-coded frame using the first coding mode with overlapping window and the second frame using the second coding mode with non-overlapping window.