Oversampling in a combined transposer filter bank

摘要

The present invention relates to coding of audio signals, and in particular to high frequency reconstruction methods including a frequency domain harmonic transposer. A system and method for generating a high frequency component of a signal from a low frequency component of the signal is described. The system comprises an analysis filter bank (501) comprising an analysis transformation unit (601) having a frequency resolution of Δf; and an analysis window (611) having a duration of DA; the analysis filter bank (501) being configured to provide a set of analysis subband signals from the low frequency component of the signal; a nonlinear processing unit (502, 650) configured to determine a set of synthesis subband signals based on a portion of the set of analysis subband signals, wherein the portion of the set of analysis subband signals is phase shifted by a transposition order T; and a synthesis filter bank (504) comprising a synthesis transformation unit (602) having a frequency resolution of QΔf; and a synthesis window (612) having a duration of Ds; the synthesis filter bank (504) being configured to generate the high frequency component of the signal from the set of synthesis subband signals; wherein Q is a frequency resolution factor with Q≧1 and smaller than the transposition order T; and wherein the value of the product of the frequency resolution Δf and the duration DA of the analysis filter bank is selected based on the frequency resolution factor Q.

主权项

1. A system configured to generate a high frequency component of an audio signal from a low frequency component of the audio signal, comprising:
an analysis filter bank comprising an analysis transformation unit having a frequency resolution of Δf; and an analysis window having a duration of DA; the analysis filter bank being configured to provide a set of analysis subband signals from the low frequency component of the signal; a nonlinear processing unit configured to determine a set of synthesis subband signals based on a portion of the set of analysis subband signals, wherein the portion of the set of analysis subband signals is phase shifted by a transposition order T; and a synthesis filter bank comprising a synthesis transformation unit having a frequency resolution of QΔf; and a synthesis window having a duration of DS; the synthesis filter bank being configured to generate the high frequency component of the signal from the set of synthesis subband signals;wherein Q is a frequency resolution factor with Q≧1 and smaller than the transposition order T; and wherein the value of the product of the frequency resolution Δf and the duration DA of the analysis filter bank is selected based on the frequency resolution factor Q.