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: receiving an encoded audio bitstream, the encoded audio bitstream including audio data representing a lowband portion of the audio signal and high frequency reconstruction metadata; decoding the audio data to generate a decoded lowband audio signal; 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 a 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, and wherein the backwardcompatible extension container further includes a flag indicating whether additional preprocessing is used to avoid discontinuities in a shape of a spectral envelope of the highband portion when the patching mode parameter equals the first value; 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 the highband portion of the audio signal includes spectral translation if the patching mode parameter is the first value and the regenerating the highband portion of the audio signal includes harmonic transposition by phase-vocoder frequency spreading if the patching mode parameter is the second value.