Method and apparatus for encoding and decoding an audio signal using adaptively switched temporal resolution in the spectral domain

US8095359B2 · kind B2 · utility

Assignee

• Thomson Licensing · FR

Inventors

• Johannes Boehm · Göttingen, DE
• Sven Kordon · Wunstorf, DE

Key dates

• Filing date: Jun 4, 2008
• Grant date: Jan 10, 2012
• Expiry date: Nov 10, 2030

Classification

• Technology area (CPC G): Physics
• CPC primary: G10L19/022
• WIPO field: Computer technology
• WIPO sector: Electrical engineering

Abstract

Perceptual audio codecs make use of filter banks and MDCT in order to achieve a compact representation of the audio signal, by removing redundancy and irrelevancy from the original audio signal. During quasi-stationary parts of the audio signal a high frequency resolution of the filter bank is advantageous in order to achieve a high coding gain, but this high frequency resolution is coupled to a coarse temporal resolution that becomes a problem during transient signal parts by producing audible pre-echo effects. The invention achieves improved coding/decoding quality by applying on top of the output of a first filter bank a second non-uniform filter bank, i.e. a cascaded MDCT. The inventive codec uses switching to an additional extension filter bank (or multi-resolution filter bank) in order to re-group the time-frequency representation during transient or fast changing audio signal sections. By applying a corresponding switching control, pre-echo effects are avoided and a high coding gain and a low coding delay are achieved.