Coding of multichannel audio content

Patent metadata

Field	Value
Publication number	US-9646619-B2
Application number	US-201414916176-A
Country	US
Kind code	B2
Filing date	Sep 8, 2014
Priority date	Sep 12, 2013
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

There are provided decoding and encoding methods for encoding and decoding of multichannel audio content for playback on a speaker configuration with N channels. The decoding method comprises decoding, in a first decoding module, M input audio signals into M mid signals which are suitable for playback on a speaker configuration with M channels; and for each of the N channels in excess of M channels, receiving an additional input audio signal corresponding to one of the M mid signals and decoding the input audio signal and its corresponding mid signal so as to generate a stereo signal including a first and a second audio signal which are suitable for playback on two of the N channels of the speaker configuration.

First claim

The invention claimed is:

1. A method for a decoder for decoding a plurality of input audio signals for playback on a speaker configuration with N channels, the plurality of input audio signals representing encoded multichannel audio content corresponding to K≧N channels, comprising:
from the encoded multichannel audio content corresponding to K channels, extracting M input audio signals, wherein 1<M≦N≦2M;
wherein if N=M, the method further comprises the step of:
discarding any remaining signals in the encoded multichannel audio content;

decoding, in a first decoding module, the M input audio signals into M mid signals which are suitable for playback on a speaker configuration with M channels;
wherein if N>M, the method further comprises the steps of:
from the encoded multichannel audio content corresponding to K channels, extracting N-M additional input audio signals, wherein each of the additional input audio signals corresponds to one of the M mid signals and is either a side signal or a complementary signal which together with the mid signal to which it corresponds and a weighting parameter a allows reconstruction of a side signal; and for each of the N channels in excess of M channels
decoding, in a stereo decoding module, the additional input audio signal and the mid signal to which it corresponds so as to generate a stereo signal including a first and a second audio signal which are suitable for playback on two of the N channels of the speaker configuration;

whereby N audio signals are generated.

2. The method of claim 1 , wherein the stereo decoding module is operable in at least two configurations depending on a bit rate at which the decoder receives data, the method further comprising receiving an indication regarding which of the at least two configurations to use in the step of decoding the additional input audio signal and its corresponding mid signal.

3. The method of claim 1 , wherein the step of receiving an additional input audio signal comprises:
receiving a pair of audio signals corresponding to a joint encoding of an additional input audio signal corresponding to a first of the M mid signals, and an additional input audio signal corresponding to a second of the M mid signals; and
decoding the pair of audio signals so as to generate the additional input audio signals corresponding to the first and the second of the M mid signals, respectively.

4. The method of claim 2 , wherein the additional input audio signal is a waveform-coded signal comprising spectral data corresponding to frequencies up to a first frequency, and the corresponding mid signal is a waveform-coded signal comprising spectral data corresponding to frequencies up to a frequency which is larger than the first frequency, and wherein the step of decoding the additional input audio signal and its corresponding mid signal according to the first configuration of the stereo decoding module comprises the steps of:
if the additional audio input signal is in the form of a complementary signal, calculating a side signal for frequencies up to the first frequency by multiplying the mid signal with the weighting parameter a and adding the result of the multiplication to the complementary signal; and
upmixing the mid signal and the side signal so as to generate a stereo signal including a first and a second audio signal, wherein for frequencies below the first frequency the upmixing comprises performing an inverse sum-and-difference transformation of the mid signal and the side signal, and for frequencies above the first frequency the upmixing comprises performing parametric upmixing of the mid signal.

5. The method according to claim 4 , wherein the waveform-coded mid signal comprises spectral data corresponding to frequencies up to a second frequency, the method further comprising:
extending the mid signal to a frequency range above the second frequency by performing high frequency reconstruction prior to performing parametric upmixing.

6. The method of claim 2 , wherein the additional input audio signal and the corresponding mid signal are waveform-coded signals comprising spectral data corresponding to frequencies up to a second frequency, and the step of decoding the additional input audio signal and its corresponding mid signal according to the second configuration of the stereo decoding module comprises the steps of:
if the additional audio input signal is in the form of a complementary signal, calculating a side signal by multiplying the mid signal with the weighting parameter a and adding the result of the multiplication to the complementary signal; and
performing an inverse sum-and-difference transformation of the mid signal and the side signal so as to generate a stereo signal including a first and a second audio signal.

7. A computer program product comprising a non-transitory computer-readable medium with instructions for performing the method of claim 1 .

8. A decoder for decoding a plurality of input audio signals for playback on a speaker configuration with N channels, the plurality of input audio signals representing encoded multichannel audio content corresponding to K≧N channels, comprising:
a receiver that extracts M input audio signals and N-M additional input audio signals from the encoded multichannel audio content corresponding to K channels, wherein 1<M≦N≦2M;
a first decoder that decodes the M input audio signals into M mid signals which are suitable for playback on a speaker configuration with M channels;
a second decoder comprising a stereo coding module for each of the N channels in excess of M channels, wherein the stereo coding module:
receives an additional input audio signal corresponding to one of the M mid signals, the additional input audio signal being either a side signal or a complementary signal which together with the mid signal to which it corresponds and a weighting parameter a allows reconstruction of a side signal; and
decodes the additional input audio signal and its corresponding mid signal so as to generate a stereo signal including a first and a second audio signal which are suitable for playback on two of the N channels of the speaker configuration;
wherein the second decoding module is configured to act as a pass through for all of the M mid signal which are not inputted to a stereo coding module, and optionally to perform high frequency reconstruction of the one or more mid signals of all of the M mid signal which are not inputted to a stereo coding module prior to let the signals pass through,
whereby the decoder is configured to generate N audio signals.

9. A method for an encoder for encoding a plurality of input audio signals representing multichannel audio content corresponding to K channels, comprising:
receiving K input audio signals corresponding to the channels of a speaker configuration with K channels;
generating M mid signals which are suitable for playback on a speaker configuration with M channels, wherein 1<M≦K≦2M, and K-M output audio signals from the K input audio signals,
wherein 2M-K of the mid signals each corresponds to a respective one of 2M-K of the input audio signals; and
wherein the K-M mid signals not corresponding to any of the input audio signals and the K-M output audio signals are generated by, for each value of K exceeding M:
encoding, in a stereo encoding module, two of the K input audio signals so as to generate a mid signal and an output audio signal, the output audio signal being either a side signal or a complementary signal which together with the mid signal and a weighting parameter a allows reconstruction of a side signal;

encoding, in a second encoding module, the M mid signals into M additional output audio channels; and
including the K-M

Assignees

• Dolby Int Ab

Inventors

• Purnhagen Heiko
• Mundt Harald
• Kjoerling Kristofer

Classifications

• H04S2420/03

  Application of parametric coding in stereophonic audio systems · CPC title

• H04S5/00

  Pseudo-stereo systems, e.g. in which additional channel signals are derived from monophonic signals by means of phase shifting, time delay or reverberation · CPC title

• G10L19/24

  Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding · CPC title

• 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

• G10L19/02

  using spectral analysis, e.g. transform vocoders or subband vocoders · CPC title