US 12,170,091 B2
Sound signal encoding method, sound signal decoding method, sound signal encoding apparatus, sound signal decoding apparatus, program, and recording medium
Ryosuke Sugiura, Tokyo (JP); Takehiro Moriya, Tokyo (JP); and Yutaka Kamamoto, Tokyo (JP)
Assigned to NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
Appl. No. 17/909,654
Filed by NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
PCT Filed Mar. 9, 2020, PCT No. PCT/JP2020/010080
§ 371(c)(1), (2) Date Sep. 6, 2022,
PCT Pub. No. WO2021/181472, PCT Pub. Date Sep. 16, 2021.
Prior Publication US 2023/0109677 A1, Apr. 13, 2023
Int. Cl. G10L 19/008 (2013.01); G10L 19/005 (2013.01); G10L 19/022 (2013.01)
CPC G10L 19/008 (2013.01) [G10L 19/005 (2013.01); G10L 19/022 (2013.01)] 19 Claims
OG exemplary drawing
 
1. A sound signal coding method for coding an input sound signal on a frame-by-frame basis, the sound signal coding method comprising:
obtaining a downmix signal that is a signal obtained by mixing a left channel input sound signal that is input and a right channel input sound signal that is input;
obtaining a left channel subtraction gain α and a left channel subtraction gain code Cα that is a code representing the left channel subtraction gain α, from the left channel input sound signal and the downmix signal;
obtaining a sequence of values xL(t)−α×xM(t) obtained by subtracting a value obtained by multiplying a sample value xM(t) of the downmix signal and the left channel subtraction gain α from a sample value xL(t) of the left channel input sound signal, per corresponding sample t, as a left channel difference signal;
obtaining a right channel subtraction gain β and a right channel subtraction gain code Cβ that is a code representing the right channel subtraction gain β, from the right channel input sound signal and the downmix signal;
obtaining a sequence of values xR(t)−β×xM(t) obtained by subtracting a value obtained by multiplying a sample value xM(t) of the downmix signal and the right channel subtraction gain β from a sample value xR(t) of the right channel input sound signal, per corresponding sample t, as a right channel difference signal;
obtaining a monaural code CM by coding the downmix signal; and
obtaining a stereo code CS by coding the left channel difference signal and the right channel difference signal,
wherein assuming that the number of bits used for coding the downmix signal in the obtaining of the monaural code CM is bM, the number of bits used for coding the left channel difference signal in the obtaining of the stereo code CS is bL, and the number of bits used for coding the right channel difference signal in the obtaining of the stereo code CS is bR,
in the obtaining of the left channel subtraction gain α and the left channel subtraction gain code Cα,
a quantized value of a multiplication value of a left channel correction coefficient cL, which is a value greater than 0 and less than 1, is 0.5 when bL=bM, is closer to 0 than 0.5 as bL is greater than bM, and is closer to 1 than 0.5 as bL is less than bM, and a normalized inner product value rL of the downmix signal in association with the left channel input sound signal is obtained as the left channel subtraction gain α, and a code corresponding to the left channel subtraction gain α or a quantized value of the normalized inner product value rL is obtained as the left channel subtraction gain code Cα, and
in the obtaining of the right channel subtraction gain β and the right channel subtraction gain code Cβ,
a quantized value of a multiplication value of a right channel correction coefficient cR, which is a value greater than 0 and less than 1, is 0.5 when bR=bM, is closer to 0 than 0.5 as bR is greater than bM, and is closer to 1 than 0.5 as bR is less than bM, and a normalized inner product value rR of the downmix signal in association with the right channel input sound signal is obtained as the right channel subtraction gain β, and a code corresponding to the right channel subtraction gain β or a quantized value of the normalized inner product value rR is obtained as the right channel subtraction gain code Cβ.