Efficient and scalable parametric stereo coding for low bitrate audio coding applications

• US 9,799,340 B2
• Filed: 03/14/2017
• Issued: 10/24/2017
• Est. Priority Date: 07/10/2001
• Status: Expired due to Term

• Current Assignee: Dolby International AB (Dolby Laboratories Incorporated)
• Original Assignee: Dolby International AB (Dolby Laboratories Incorporated)
• Inventors: Henn, Fredrik, Kjoerling, Kristofer, Liljeryd, Lars G., Roeden, Karl Jonas, Engdegard, Jonas
• Primary Examiner(s): Chin, Vivian
• Assistant Examiner(s): SUTHERS, DOUGLAS JOHN
• Application Number:
  US15/458,135
• Publication Number:
  US 20170186435A1
• Time in Patent Office: 224 Days
• Field of Search: 381 17- 23, 700 94, 7042001, 704500-501
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: G10L 19/265 Pre-filtering, e.g. high frequency emphasis prior to encoding
• CPC Class Codes: G10L 21/038 using band spreading techniques
• CPC Class Codes: G10L 25/21 the extracted parameters being power information

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.

Claims

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 frequency.

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 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 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 frequency.

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 frequency.