Apparatus and method for stereo audio encoding of digital audio signal data
First Claim
1. A stereo audio encoding method for encoding audio signals to left and right reproduced signals, comprising the steps of:
- (a) calculating a correlation between left and right original signals to detect a pair of the left and right original signals having opposite phase characteristics and a pair of the left and right original signals having same phase characteristics, where the audio signals have been transformed to the left and right original signals each defined by a train of frames where each frame contains a plurality of sampled data;
(b) processing the left and right original signals having the opposite phase characteristics according to a power equalization method to obtain said left and right reproduced signals; and
(c) processing the left and right original signals having the same phase characteristics according to an error minimization method to obtain said left and right reproduced signals.
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Abstract
A stereo audio encoding method for encoding left and right original signals to a left and right reproduced signals for suppressing a loss of quality in the reproduced audio signal. The correlation between the right and left channel signals is determined, and the phase of each signal is compared. If the two signals have the same phase, a modified scale factor is calculated based on a power equalization method, but if the two signals are in opposite phase, another modified scale factor is calculated based on an error minimization method. The modified scale factors are used for calculating the reproduced signals.
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Citations
14 Claims
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1. A stereo audio encoding method for encoding audio signals to left and right reproduced signals, comprising the steps of:
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(a) calculating a correlation between left and right original signals to detect a pair of the left and right original signals having opposite phase characteristics and a pair of the left and right original signals having same phase characteristics, where the audio signals have been transformed to the left and right original signals each defined by a train of frames where each frame contains a plurality of sampled data; (b) processing the left and right original signals having the opposite phase characteristics according to a power equalization method to obtain said left and right reproduced signals; and (c) processing the left and right original signals having the same phase characteristics according to an error minimization method to obtain said left and right reproduced signals. - View Dependent Claims (3, 4, 5, 6, 7)
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2. A stereo audio encoding method as claimed in 1, wherein said processing step (b) comprises the steps of:
- adding said left and right original signals; and
dividing the added signal into left and right reproduced signals relative to a first ratio between (1) a maximum absolute data of an average signal which is an average between said left and right original signals to (2) a maximum absolute sampled data in the left and right original signals and also to a second ratio between (1) a power of the left original signal to (2) a power of d right original signal.
- adding said left and right original signals; and
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8. A stereo audio encoding apparatus for encoding audio signals to left and right reproduced signals, said apparatus comprising:
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calculating means for calculating a correlation between left and right original signals to detect a pair of the left and right original signals having opposite phase characteristics and a pair of the left and right original signals having same phase characteristics, where the audio signals have been transformed to the left and right original signals each defined by a train of frames where each frame contains a plurality of sampled data; first processing means for processing said left and right original signals having the opposite phase characteristics according to a power equalization method to obtain said left and right reproduced signals; and second processing means for processing said left and right original signals having the same phase characteristics according to an error minimization method to obtain said left and right reproduced signals.
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9. A stereo audio encoding method for encoding audio signals to produce modified scale factors, comprising the steps of:
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(a) calculating a correlation between left and right original signals to detect a pair of the left and right original signals having opposite phase characteristics and a pair of the left and right original signals having same phase characteristics where the audio signals have been transformed to the left and right original signals each defined by a train of frames where each frame contains a plurality of sampled data; (b) processing said left and right original signals having the opposite phase characteristics according to a power equalization method to obtain left and right scale factor modifiers; and (c) processing said left and right original signals having the same phase characteristics according to an error minimization method to obtain left and right scale factor modifiers. - View Dependent Claims (10, 11, 12, 13)
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14. A stereo audio encoding apparatus for encoding audio signals to produce modified scale factors, said apparatus comprising:
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calculating means for calculating a correlation between left and right original signals to detect a pair of the left and right original signals having opposite phase characteristics and a pair of the left and right original signals having same phase characteristics, where the audio signals have been transformed to the left and right original signals each defined by a train of frames where each frame contains a plurality of sampled data; first processing means for processing said left and right original signals having the opposite phase characteristics according to a power equalization method to obtain the left and right scale factor modifiers; and second processing means for processing said left and right original signals having the same phase characteristics according to an error minimization method to obtain the left and right scale factors modifiers.
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Specification