Method for reduction of aliasing introduced by spectral envelope adjustment in real-valued filterbanks
The present invention proposes a new method for improving the performance of a real-valued filterbank based spectral envelope adjuster. By adaptively locking the gain values for adjacent channels dependent on the sign of the channels, as defined in the application, reduced aliasing is achieved. Furthermore, the grouping of the channels during gain-calculation, gives an improved energy estimate of the real valued subband signals in the filterbank.
1. Apparatus for assessing an energy of a signal having audio subband signals generated by filtering the signal using a real-valued analysis filterbank, the real-valued filterbank having subband filters, adjacent subband filters of the real-valued filterbank having transition bands overlapping in an overlapping range, comprising:
an examiner for examining an audio subband signal originating from a subband filter and an adjacent audio subband signal originating from an adjacent subband filter, to determine whether the audio subband signal and the adjacent audio subband signal have aliasing generating signal components in the overlapping range to obtain grouped audio subband signals in response to a result of the examination indicating that the audio subband signal and the adjacent audio subband signal have aliasing generating signal components in the overlapping range; and
a calculator for calculating an energy estimate for an energy in the grouped adjacent audio subband signals,
wherein the apparatus for assessing comprises a hardware implementation.
2. Method of assessing an energy of a signal having audio subband signals generated by filtering the signal using a real-valued analysis filterbank, the real-valued filterbank having subband filters, adjacent subband filters of the real-valued filterbank having transition bands overlapping in an overlapping range, comprising:
examining an audio subband signal originating from a subband filter and an adjacent audio subband signal originating from an adjacent subband filter, to determine whether the audio subband signal and the adjacent audio subband signal have aliasing generating signal components in the overlapping range to obtain grouped audio subband signals in response to a result of the examination indicating that the audio subband signal and the adjacent audio subband signal have aliasing generating signal components in the overlapping range; and
calculating an energy estimate for an energy in the grouped adjacent audio subband signals,
wherein the method for assessing comprises a hardware implementation.
3. Non-transitory digital storage medium having stored thereon a computer program having a program code for performing the method in accordance with claim 2 , when the computer program runs on a computer.