Efficient and Scalable Parametric Stereo Coding for Low Bitrate Audio Coding Applications

Patent metadata

Field	Value
Publication number	US-2017186435-A1
Application number	US-201715458135-A
Country	US
Kind code	A1
Filing date	Mar 14, 2017
Priority date	Jul 10, 2001
Publication date	Jun 29, 2017
Grant date	—

Abstract

The present invention provides improvements to prior art audio codecs that generate a stereo-illusion through post-processing of a received mono signal. These improvements are accomplished by extraction of stereo-image describing parameters at the encoder side, which are transmitted and subsequently used for control of a stereo generator at the decoder side. Furthermore, the invention bridges the gap between simple pseudo-stereo methods, and current methods of true stereo-coding, by using a new form of parametric stereo coding. A stereo-balance parameter is introduced, which enables more advanced stereo modes, and in addition forms the basis of a new method of stereo-coding of spectral envelopes, of particular use in systems where guided HFR (High Frequency Reconstruction) is employed. As a special case, the application of this stereo-coding scheme in scalable HFR-based codecs is described.

First claim

1 . A decoder configured to decode an encoded bitstream, the decoder comprising:
a demultiplexer for demultiplexing the encoded bitstream for obtaining a lowband core decoder signal, level parameters, and balance parameters; a lowband core decoder for producing a lowband output signal, the lowband output signal having a lowband mono signal or a lowband stereo signal; and a high-frequency reconstruction device for generating a synthetic highband using the lowband output signal, the level parameters, and the balance parameters and for combining the synthetic highband and the lowband output signal, wherein the level parameters represent a total power in a frequency band of a signal having two channels, wherein the total power represents an energy average of a left channel and a right channel for a given time segment and frequency band, wherein the balance parameters represent a quotient of an energy of the left channel and an energy of the right channel, wherein the level parameters are delta coded in frequency.

2 . A method for decoding an encoded bitstream, the method comprising:
demultiplexing the encoded bitstream for obtaining a lowband core decoder signal, level parameters, and balance parameters; producing a lowband output signal, the lowband output signal having a lowband mono signal or a lowband stereo signal; and generating a synthetic highband using the lowband output signal, the level parameters, and the balance parameters; combining the synthetic highband and the lowband output signal, wherein the level parameters represent a total power in a frequency band of a signal having two channels, wherein the total power represents an energy average of a left channel and a right channel for a given time segment and frequency band, wherein the balance parameters represent a quotient of an energy of the left channel and an energy of the right channel, wherein the level parameters are delta coded in frequency.

3 . A decoder configured to decode an encoded bitstream, the decoder comprising:
a demultiplexer for demultiplexing the encoded bitstream for obtaining a lowband core decoder signal, level parameters, and stereo width parameters; a lowband core decoder for producing a lowband output signal, the lowband output signal having a lowband mono signal or a lowband stereo signal; a high-frequency reconstruction device for generating a synthetic highband using the lowband output signal and for combining the synthetic highband and the lowband output signal to produce a combined signal; and a parametric stereo decoder for generating a stereo signal from the combined signal using the level parameters and the stereo width parameters, wherein the level parameters represent a total power in a frequency band of a signal having two channels, wherein the total power is derived from an energy average of a left channel and a right channel for a given time segment and frequency band, wherein the stereo width parameters represents a degree of similarity between a first channel and a second channel, and wherein the level parameters are delta coded in frequency.

4 . A method for decoding an encoded bitstream, the method comprising:
demultiplexing the encoded bitstream for obtaining a lowband core decoder signal, level parameters, and stereo width parameters; producing a lowband output signal, the lowband output signal having a lowband mono signal or a lowband stereo signal; generating a synthetic highband using the lowband output signal; combining the synthetic highband and the lowband output signal to produce a combined signal; and generating a stereo signal from the combined signal using the level parameters and the stereo width parameters, wherein the level parameters represent a total power in a frequency band of a signal having two channels, wherein the total power is derived from an energy average of a left channel and a right channel for a given time segment and frequency band, wherein the stereo width parameters represent a degree of similarity between a first channel and a second channel, and wherein the level parameters are delta coded in frequency.

Assignees

• Dolby Int Ab

Inventors

• Henn Fredrik
• Kjoerling Kristofer
• Liljeryd Lars G
• Roeden Karl Jonas
• Engdegard Jonas

Classifications

• G10L19/008 Primary

  Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing · CPC title

• G10L21/038

  using band spreading techniques · CPC title

• G10L19/265

  Pre-filtering, e.g. high frequency emphasis prior to encoding · CPC title

• G10L25/21

  the extracted parameters being power information · CPC title