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

• US 10,540,982 B2
• Filed: 04/30/2019
• Issued: 01/21/2020
• 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, Kjorling, Kristofer, Liljeryd, Lars, Roden, Jonas, Engdegard, Jonas
• Primary Examiner(s): Chin, Vivian C
• Assistant Examiner(s): Suthers, Douglas J
• Application Number:
  US16/399,705
• Publication Number:
  US 20190259394A1
• Time in Patent Office: 266 Days
• Field of Search: 381 17- 18, 381 19- 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 for decoding a bit stream comprising an encoded lowband signal and an encoded power spectral envelope of a stereo or multichannel signal having a first channel and a second channel, the decoder comprising one or more processing elements that:

receive the encoded lowband signal included in the bitstream;

produce a lowband output signal, the lowband output signal having a lowband stereo signal;

receive the encoded power spectral envelope of the stereo signal or the multichannel signal having the first channel and the second channel, the first channel and the second channel having a set of frequency bands, the encoded power spectral envelope being represented by a balance parameter for each frequency band and a level parameter representing a total power of the first channel and the second channel for each frequency band;

convert the balance parameters and the level parameters into power values of the first channel and the second channel;

generate a synthetic highband signal using the lowband output signal;

adjust a spectral envelope of the synthetic highband signal using the power values of the first channel and the second channel to obtain an adjusted highband signal; and

combine the adjusted highband signal and the lowband output signal to obtain a decoded stereo signal or a decoded multichannel signal.

2. A method of decoding a bit stream comprising an encoded lowband signal and an encoded power spectral envelope of a stereo or multichannel signal having a first channel and a second channel, the method comprising:

receiving the encoded lowband signal included in the bit stream;

producing a lowband output signal, the lowband output signal having a lowband stereo signal;

receiving the encoded power spectral envelope of the stereo signal or the multichannel signal having the first channel and the second channel, the first channel and the second channel having a set of frequency bands, the encoded power spectral envelope being represented by a balance parameter for each frequency band and a level parameter representing a total power of the first channel and the second channel for each frequency band;

converting the balance parameters and the level parameters into power values of the first channel and the second channel;

generating a synthetic highband signal using the lowband output signal;

adjusting a spectral envelope of the synthetic highband signal using the power values of the first channel and the second channel to obtain an adjusted highband signal; and

combining the adjusted highband signal and the lowband output signal to obtain a decoded stereo signal or a decoded multichannel signal.

3. A non-transitory storage medium having stored thereon a computer program for performing a method of decoding a bit stream comprising an encoded lowband signal and an encoded power spectral envelope of a stereo or multichannel signal having a first channel and a second channel, the method comprising:

receiving the encoded lowband signal included in the bit stream;

producing a lowband output signal, the lowband output signal having a lowband stereo signal, wherein the lowband core decoder is configured for receiving the encoded lowband signal included in the bit stream;

receiving the encoded power spectral envelope of the stereo signal or the multichannel signal having the first channel and the second channel, the first channel and the second channel having a set of frequency bands, the encoded power spectral envelope being represented by a balance parameter for each frequency band and a level parameter representing a total power of the first channel and the second channel for each frequency band;

converting the balance parameters and the level parameters into power values of the first channel and the second channel;

generating a synthetic highband signal using the lowband output signal;

adjusting a spectral envelope of the synthetic highband signal using the power values of the first channel and the second channel to obtain an adjusted highband signal; and

combining the adjusted highband signal and the lowband output signal to obtain a decoded stereo signal or a decoded multichannel signal.