Spectral Translation/Folding in the Subband Domain

摘要

The present invention relates to a new method and apparatus for improvement of High Frequency Reconstruction (HFR) techniques using frequency translation or folding or a combination thereof. The proposed invention is applicable to audio source coding systems, and offers significantly reduced computational complexity. This is accomplished by means of frequency translation or folding in the subband domain, preferably integrated with spectral envelope adjustment in the same domain. The concept of dissonance guard-band filtering is further presented. The proposed invention offers a low-complexity, intermediate quality HFR method useful in speech and natural audio coding applications.

主权项

1. A method for decoding coded signals, the coded signals comprising a coded lowband audio signal, comprising:
separating the coded lowband audio signal from the coded signals; audio decoding the coded lowband audio signal to obtain a decoded audio signal; obtaining an envelope adjusted and frequency-translated signal, comprising: filtering the decoded audio signal using an analysis filterbank to obtain complex-valued subband signals within a source range, wherein each complex-valued subband signal is represented by a real-valued component and an imaginary-valued component; patching the real-valued component and the imaginary-valued component of a complex-valued subband signal with index i within the source range to a complex-valued subband signal with index j within a reconstruction range, wherein the source range comprises frequencies lower than frequencies in the reconstruction range; patching the real-valued component and the imaginary-valued component of a complex-valued subband signal with index i+1 within the source range to a complex-valued subband signal with index j+1 within a reconstruction range; applying an envelope adjustment to the patched complex-valued subband signals within the reconstruction range; and filtering the patched and envelope adjusted complex-valued subband signals within the reconstruction range using a synthesis filterbank to obtain the envelope adjusted and frequency translated signal.