Efficient and scalable parametric stereo coding for low bitrate applications

Patent metadata

Field	Value
Publication number	US-9792919-B2
Application number	US-201715458126-A
Country	US
Kind code	B2
Filing date	Mar 14, 2017
Priority date	Jul 10, 2001
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

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

The invention claimed is:

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;
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 to form a combined signal, and
an output interface for outputting the combined signal,
wherein the level parameters represent a total power in a frequency band of a signal having two channels,
wherein the total power represents a sum of an energy of a left channel and an energy of 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 time.

2. A method for decoding an encoded bitstream, the method comprising:
demultiplexing, by a demultiplexer, the encoded bitstream for obtaining a lowband core decoder signal, level parameters, and balance parameters;
producing, by a lowband decoder, a lowband output signal, the lowband output signal having a lowband mono signal or a lowband stereo signal;
generating, by a high-frequency reconstruction device, a synthetic highband using the lowband output signal, the level parameters, and the balance parameters;
combining the synthetic highband and the lowband output signal to form a combined signal, and
outputting the combined signal,
wherein the level parameters represent a total power in a frequency band of a signal having two channels,
wherein the total power represents a sum of an energy of a left channel and an energy of 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 time.

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 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;
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 to form a combined signal,
a parametric stereo decoder for generating a stereo audio signal from the combined signal; and
an output interface for outputting the stereo signal,
wherein the level parameters represent a total power in a frequency band of a signal having two channels,
wherein the total power represents a sum of an energy of a left channel and an energy of 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 time.

4. A method for decoding an encoded bitstream, the method comprising:
demultiplexing, by a demultiplexer, the encoded bitstream for obtaining a lowband core decoder signal, level parameters, and balance parameters;
producing, by a lowband decoder, a lowband output signal, the lowband output signal having a lowband mono signal or a lowband stereo signal;
generating, by a high-frequency reconstruction device, a synthetic highband using the lowband output signal, the level parameters, and the balance parameters;
combining the synthetic highband and the lowband output signal to form a combined signal;
generating a stereo signal from the combined signal; and
outputting the stereo signal,
wherein the level parameters represent a total power in a frequency band of a signal having two channels,
wherein the total power represents a sum of an energy of a left channel and an energy of 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 time.

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

• G10L25/21

  the extracted parameters being power information · CPC title

• G10L19/265

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