Sound signal downmixing method, sound signal coding method, sound signal downmixing apparatus, sound signal coding apparatus, program and recording medium

Patent metadata

Field	Value
Publication number	US-12165659-B2
Application number	US-202117908965-A
Country	US
Kind code	B2
Filing date	Feb 8, 2021
Priority date	Mar 9, 2020
Publication date	Dec 10, 2024
Grant date	Dec 10, 2024

Abstract

A sound signal downmix method includes an inter-channel relationship information obtaining step of obtaining an inter-channel correlation value and preceding channel information of every pair of two channels included in N channels, the inter-channel correlation value being a value indicating a degree of a correlation between input sound signals of the two channels, the preceding channel information being information indicating which of the input sound signals of the two channels is preceding, and a downmix step of obtaining a downmix signal by weighting and adding the input sound signals of the N channels, the input sound signal of each channel being weighted based on the inter-channel correlation value and the preceding channel information such that the larger a correlation with an input sound signal of a preceding channel that precedes the channel, the smaller a weight, whereas the larger a correlation with an input sound signal of a succeeding channel that succeeds the channel, the larger the weight.

First claim

The invention claimed is:

1. A sound signal downmix method of obtaining a downmix signal that is a monaural sound signal from input sound signals of N channels, N being an integer of three or greater, the sound signal downmix method comprising:
an inter-channel relationship information obtaining step of obtaining an inter-channel correlation value and preceding channel information of every pair of two channels included in the N channels, the inter-channel correlation value being a value indicating a degree of a correlation between input sound signals of the two channels, the preceding channel information being information indicating which of the input sound signals of the two channels is preceding; and
a downmix step of obtaining the downmix signal by weighting and adding the input sound signals of the N channels, the input sound signal of each channel being weighted based on the inter-channel correlation value and the preceding channel information such that the larger a correlation with an input sound signal of a preceding channel that precedes the channel, the smaller a weight, whereas the larger a correlation with an input sound signal of a succeeding channel that succeeds the channel, the larger the weight.

2. The sound signal downmix method according to claim 1 , wherein
the inter-channel correlation value is a value from 0 to 1,
a sample number is denoted as t, every sample of the input sound signal of an ith channel whose i is from 1 to N is denoted as x i (t), and every sample of the downmix signal is denoted as x M (t), and
the downmix step include obtaining every sample x M (t) of the downmix signal, wherein
a set of channel numbers of channels preceding the ith channel is denoted as I Li ,
a set of channel numbers of channels succeeding the ith channel is denoted as I Fi ,
the inter-channel correlation value of a pair of the ith channel and every channel j preceding the ith channel is denoted as γ ij ,

the inter-channel correlation value of a pair of the ith channel and every channel k succeeding the ith channel is denoted as γ ik ,
a weight of the ith channel is denoted as w i , w i being expressed by

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3. A sound signal coding method comprising:
the sound signal downmix method according to claim 1 as a sound signal downmix step;
a monaural coding step of obtaining a monaural code by coding the downmix signal obtained in the downmix step; and
a stereo coding step of obtaining a stereo code by coding the input sound signals of the N channels.

4. A sound signal downmix apparatus configured to obtain a downmix signal that is a monaural sound signal from input sound signals of N channels, N being an integer of three or greater, the sound signal downmix apparatus comprising:
an inter-channel relationship information obtaining unit configured to obtain an inter-channel correlation value and preceding channel information of every pair of two channels included in the N channels, the inter-channel correlation value being a value indicating a degree of a correlation between input sound signals of the two channels, the preceding channel information being information indicating which of the input sound signals of the two channels

Assignees

• Nippon Telegraph & Telephone

Inventors

• Sugiura Ryosuke
• Moriya Takehiro
• Kamamoto Yutaka

Classifications

• G10L19/16

  Vocoder architecture · 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

• H04S1/007

  in which the audio signals are in digital form (data reduction aspects thereof based on psychoacoustics G10L19/02) · 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

• H04S2400/03

  Aspects of down-mixing multi-channel audio to configurations with lower numbers of playback channels, e.g. 7.1 -> 5.1 (H04S2400/01 takes precedence) · CPC title