A method for decoding an encoded audio bitstream to perform high frequency reconstruction of an audio signal

Abstract

The present invention relates to a method for performing high frequency reconstruction of an audio signal, the method comprising: decoding an encoded audio bitstream to generate a decoded lowband audio signal, wherein the encoded audio bitstream further includes a fill element with an identifier indicating a start of the fill element and fill data after the identifier, wherein the fill data includes a backwardcompatible extension container, and wherein the identifier is a three bit unsigned integer transmitted most significant bit first and having a value of 0x6; extracting from the encoded audio bitstream the high frequency reconstruction metadata, the high frequency reconstruction metadata including operating parameters for a high frequency reconstruction process, the operating parameters including a patching mode parameter located in the backward-compatible extension container of the encoded audio bitstream, wherein a first value of the patching mode parameter indicates spectral translation and a second value of the patching mode parameter indicates harmonic transposition by phase-vocoder frequency spreading; filtering the decoded lowband audio signal to generate a filtered lowband audio signal; regenerating a highband portion of the audio signal using the filtered lowband audio signal and the high frequency reconstruction metadata, wherein the regenerating includes spectral translation if the patching mode parameter is the first value and the regenerating includes harmonic transposition by phase-vocoder frequency spreading if the patching mode parameter is the second value; and combining the filtered lowband audio signal with the regenerated highband portion to form a wideband audio signal.