Virtual playback method for surround-sound in multi-channel three-dimensional space
View Patent ↗Disclosed in the invention is a virtual reproduction method for a multichannel spatial surround sound in three-dimensional space. Multichannel spatial surround sound signals are undergone a sum and difference operation and processed with virtual reproduction signal processing functions, then fed to four actual loudspeakers arranged at left-front-up and right-front-up directions on a high elevation plane of 30°±10° and horizontal left-front and right-front directions for reproduction, and generate a auditory effect of spatial surround sound. The invention simplifies the number and arrangement of loudspeakers required for multichannel spatial surround sound reproduction, and is suitable for cases in which the arrangement of multiple loudspeakers for spatial surround sound is infeasible, such as in a TV set, and so on.
1. A virtual reproduction method for a multichannel spatial surround sound in a three-dimensional space, the method comprising: the following steps:
step 1: arranging four loudspeakers at directions of left-front, right-front in a horizontal plane and at directions of left-front-up, right-front-up on an elevation plane with an elevation angle of 30°±15° respectively, wherein the elevation angle is measured from a listening position on the horizontal plane;
step 2: inputting M non-front and non-back channel signals E 1 , E 2 , . . . E M of an original spatial surround sound in a horizontal layer, and a front channel signal E M+1 and a back channel signal E M+2 if the front channel signal E M+1 and a back channel signal E M+2 exist, wherein M is an even number; and numbering M channel signals according to a rule that an odd number represents a left half-space channel and an even number represents a symmetric right half-space channel;
step 3: inputting M′ non-front and non-back channel signals E′ 1 , E′ 2 , . . . E′ M′ of the original spatial surround sound in an upper layer, and a front channel signal E′ M′+1 and a back channel signal E′ M′+2 if the front channel signal E′ M′+1 and the back channel signal E′ M′+2 exist wherein M′ is an even number; and numbering M′ channel signals according to a rule that an odd number represents a left half-space channel and an even number represents a symmetric right half-space channel;
step 4: for the M channel signals of the horizontal layer, carrying out a sum and difference operation on each left half-space channel signal and each symmetric right half-space channel signal to obtain M/2 sum signals (E 1 +E 2 ), (E 3 +E 4 ), . . . (E M−1 +E M ) of the horizontal layer and M/2 difference signals (E 1 −E 2 ), (E 3 −E 4 ), . . . (E M−1 −E M ) of the horizontal layer;
step 5: for the M′ channel signals of the upper layer, carrying out a sum and difference operation on each left half-space channel signal and each symmetric right half-space channel signal to obtain M′/2 sum signals (E′ 1 +E′ 2 ), (E′ 3 +E′ 4 ), . . . (E′ M′−1 +E′ M′+1 ) of the upper layer and M′/2 difference signals (E′ 1 −E′ 2 ), (E′ 3 −E′ 4 ), . . . (E′ M′−1 −E′ M′ ) of the upper layer;
step 6: filtering the M/2 sum signals of the horizontal layer with M/2 virtual reproduction signal processing functions Σ 1,2 , Σ 3,4 , . . . Σ M−1,M respectively and summing the signals, and then adding the front and back channel signals Σ M+1 and E M+2 , if the front and back channel signals E M+1 and E M+2 exist, to obtain a total sum signal E SUM =Σ 1,2 (E 1 +E 2 )+Σ 3,4 (E 3 +E 4 ), . . . +Σ M−1,M (E M +E M+1 )+E M+1 +E M+2 of the horizontal layer;
step 7: filtering the M/2 difference signals of the horizontal layer with M/2 virtual reproduction signal processing functions Δ 1,2 , Δ 3,4 . . . Δ M−1,M respectively and then summing the signals to obtain a total difference signal E DIF =Δ 1,2 (E 1 −E 2 )+Δ 3,4 (E 3 −E 4 ), . . . Δ M−1,M (E M−1 −E M ) of the horizontal layer;
step 8: filtering the M′/2 sum signals of the upper layer with M′/2 virtual reproduction signal processing functions Σ′ 1,2 , Σ′ 3,4 , . . . Σ′ M′−1,M′ respectively and summing the signals, and then adding the possible front and back channel signals E M′+1 and E M′+2 to obtain a total sum signal E′ SUM =Σ′ 1,2 (E′ 1 +E′ 2 )+Σ′ 3,4 (E′ 3 +E′ 4 ), . . . +Σ′ M′−1,M′ (E′ M′ +E′ M′+1 )+E′ M′+1 +E′ M′+2 of the upper layer;
step 9: filtering the M′/2 difference signals of the upper layer with M′/2 virtual reproduction signal processing functions Δ′ 1,2 , Δ′ 3,4 , . . . Δ′ M−1,M respectively and then summing the signals to obtain a total difference signal E′ DIF =Δ′ 1,2 (E′ 1 −E′ 2 )+Δ′ 3,4 (E′ 3 −E′ 4 ), . . . +Δ′ M′−1,M′ (E′ M′ −E′ M′+1 ) of the upper layer;
step 10: carrying out a sum and difference operation on the total sum signal E SUM and the total difference signal E DIF of the horizontal layer, attenuating them to respectively obtain reproduced signals for actual loudspeakers at left-front and right-front directions in the horizontal plane, and feeding the signals to corresponding actual loudspeakers for reproduction; and
step 11: carrying out a sum and difference operation on the total sum signal E′ SUM and the total difference signal E′ DIF of the upper layer, attenuating them to respectively obtain reproduction signals of actual loudspeakers at left-front-up and right-front-up directions, and feeding the signals to corresponding actual loudspeakers for reproduction.
2. The virtual reproduction method for the multichannel spatial surround sound in three-dimensional space according to claim 1 , wherein in the step 10, the sum and difference operation is carried out on the total sum signal E SUM and the total difference signal E DIF of the horizontal layer, and the signals are attenuated by −3 dB, which is, multiplied by 0.7 to respectively obtain the reproduction signals E L1 =0.7 (E SUM +E DIF ) and E R1 =0.7 (E SUM −E DIF ) of the actual loudspeakers at left-front and right-front directions respectively in the horizontal plane, and the signals are fed to the corresponding actual loudspeakers for reproduction.
3. The virtual reproduction method for the multichannel spatial surround sound in three-dimensional space according to claim 1 , wherein in the step 11, the sum and difference operation is carried out on the total sum signal E′ SUM and the total difference signal E′ DIF of the upper layer, and the signals are attenuated by −3 dB, which is, multiplied by 0.7 to respectively obtain the reproduction signals E L2 =0.7 (E′ SUM +E′ DIF ) and E R2 =0.7 (E′ SUM −E′ DIF ) of the actual loudspeakers at left-front-up and right-front-up directions respectively, and the signals are fed to the corresponding actual loudspeakers for reproduction.
4. The virtual reproduction method for the multichannel spatial surround sound in three-dimensional space according to claim 1 , wherein the filtering with the M/2 virtual reproduction signal processing functions Σ 1,2 , Σ 3,4 , . . . Σ M−1,M in the step 6, and the filtering with the M/2 virtual reproduction signal processing functions Δ 1,2 , Δ 3,4 . . . Δ M−1,M in step 7 are carried out according to the virtual reproduction signal processing functions obtained by the following equations:
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wherein H L (θ m , f) and H R (θ m , f) are a pair of Head Related Transfer Functions (HRTFs) from virtual loudspeakers in a direction of azimuth θ m of the horizontal plane to left and right ears, wherein f is a frequency; and α 1 =α 1 (f) and β 1 =β 1 (f) are HRTFs from actual loudspeaker at horizontal left-front or right-front to the ipsilateral and contralateral ears, respectively.
5. The virtual reproduction method for the multichannel spatial surround sound in three-dimensional space according to claim 1 , wherein the filtering with the M′/2 virtual reproduction signal processing functions Σ′ 1,2 , Σ′ 3,4 , . . . Σ′ M′−1,M′ in the step 8, and the filtering with the M′/2 virtual reproduction signal processing functions Δ′ 1,2 , Δ′ 3,4 , . . . Δ′ M′−1,M′ in the step 9 are carried out according to virtual reproduction signal processing functions obtained by the following equations:
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wherein H L (θ′ m′ , f) and H R (θ′ m′ , f) are a pair of Head Related Transfer Functions (HRTFs) from virtual loudspeakers in a direction of θ′ m′ of the horizontal plane to left and right ears, wherein f is a frequency; and α 2 =α 2 (f) and β 2 =β 2 (f) are HRTFs from actual loudspeaker at left-front-up or right-front-up direction in the ipsilateral and contralateral ears, respectively.