Transform domain transcoding and decoding of audio data using integer-reversible modulated lapped transforms

Abstract

A 'STAC Codec' provides audio transcoding and decoding by processing an encoded audio signal using a backward-adaptive run-length Golomb-Rice (RLGR) decoder to recover transform coefficients of the encoded audio signal. The transform coefficients are then either transcoded in the transform domain to lossy or other formats, or decoded to the time domain by applying an inverse integer-reversible modulated lapped transform (MLT) to the recovered transform coefficients to recover an uncompressed time domain representation compressed audio signal. In additional embodiments, an inter-block spectral estimation and inverse data sorting strategy is used in recovering the transform coefficients from the encoded audio signal. In other embodiments, conversion from lossless encoding to near-lossless encoding is achieved by right-shifting recovered transform coefficients by some number of bits such that quantization errors are not perceived as distortion in the decoded audio signal, then re-encoding the right shifted transform coefficients.