Method and encoder for processing a digital stereo audio signal

US8891775B2 · kind B2 · utility

Assignee

• Dolby International AB · IE

Inventors

• Michael Schug · Erlangen, DE
• Harald Mundt · Fürth, DE

Key dates

• Filing date: May 7, 2012
• Grant date: Nov 18, 2014
• Expiry date: May 7, 2032

Classification

• Technology area (CPC G): Physics
• CPC primary: G10L19/03
• WIPO field: Computer technology
• WIPO sector: Electrical engineering

Abstract

The invention discloses a method and an encoder for processing a digital audio stereo signal. A digital audio encoder for coding such audio signal comprises a predictive Temporal Noise Shaping (TNS) filter, a Mid-/Side (M/S) coding unit, a control unit for determining a first prediction gain related to the unmodified L/R signal processed by the TNS filter and for determining a second prediction gain related to the M/S-coded L/R signal processed by the TNS filter, wherein the control unit is adapted to disable TNS-filtering—i.e. to bypass the TNS filter—for a current signal frame, if the first and second prediction gains differ by more than a pre-determined mismatch range. Preferably, the first and second prediction gains are determined from signal energy ratios calculated for each channel of the stereo signal including the signal energies of both the TNS-processed (unmodified) L- respectively (unmodified) R-signal and the TNS-processed M/S coded L- respectively M/S coded R-signal divided by the respective signal energies before TNS processing. Furthermore, the control unit is preferably adapted to overrule the disabling of the TNS filter, if the input signal is a near-mono audio si…