MDCT-based complex prediction stereo coding
First Claim
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1. A decoder system for providing a stereo signal by complex prediction stereo coding, the decoder system comprising:
- an upmix stage adapted to generate the stereo signal based on first frequency-domain representations of a downmix signal (M) and a residual signal (D), each of the first frequency-domain representations comprising first spectral components representing spectral content of the corresponding signal expressed in a first subspace of a multidimensional space, the upmix stage comprising;
a module for computing a second frequency-domain representation of the downmix signal based on the first frequency-domain representation thereof, the second frequency-domain representation comprising second spectral components representing spectral content of the signal expressed in a second subspace of the multidimensional space that includes a portion of the multidimensional space not included in the first subspace, wherein the module is adapted to determine the second spectral components of the downmix signal by applying a Finite Impulse Reponse (FIR) filter to the first spectral components of the downmix signal;
a weighted summer for computing a first frequency-domain representation of a side signal (S), the first frequency-domain representation of the side signal (S) comprising first spectral components representing spectral content of the side signal expressed in the first subspace of the multidimensional space, on the basis of the first and second frequency-domain representations of the downmix signal, the first frequency-domain representation of the residual signal and a complex prediction coefficient (a) encoded in a bit stream signal received by the decoder system;
wherein each spectral component represents a range of frequencies, and wherein each of the first spectral components of the side signal is determined from spectral components of the downmix signal and the residual signal representing the same range of frequencies as the first spectral component of the side signal; and
a sum-and-difference stage for computing the stereo signal on the basis of the first frequency-domain representation of the downmix signal and the side signal, wherein the upmix stage is further operable in a pass-through mode, in which said downmix and residual signals are supplied to the sum-and-difference stage directly.
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Abstract
The invention provides methods and devices for stereo encoding and decoding using complex prediction in the frequency domain. In one embodiment, a decoding method, for obtaining an output stereo signal from an input stereo signal encoded by complex prediction coding and comprising first frequency-domain representations of two input channels, comprises the upmixing steps of:
- (i) computing a second frequency-domain representation of a first input channel; and
- (ii) computing an output channel on the basis of the first and second frequency-domain representations of the first input channel, the first frequency-domain representation of the second input channel and a complex prediction coefficient. The upmixing can be suspended responsive to control data.
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Citations
14 Claims
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1. A decoder system for providing a stereo signal by complex prediction stereo coding, the decoder system comprising:
an upmix stage adapted to generate the stereo signal based on first frequency-domain representations of a downmix signal (M) and a residual signal (D), each of the first frequency-domain representations comprising first spectral components representing spectral content of the corresponding signal expressed in a first subspace of a multidimensional space, the upmix stage comprising; a module for computing a second frequency-domain representation of the downmix signal based on the first frequency-domain representation thereof, the second frequency-domain representation comprising second spectral components representing spectral content of the signal expressed in a second subspace of the multidimensional space that includes a portion of the multidimensional space not included in the first subspace, wherein the module is adapted to determine the second spectral components of the downmix signal by applying a Finite Impulse Reponse (FIR) filter to the first spectral components of the downmix signal; a weighted summer for computing a first frequency-domain representation of a side signal (S), the first frequency-domain representation of the side signal (S) comprising first spectral components representing spectral content of the side signal expressed in the first subspace of the multidimensional space, on the basis of the first and second frequency-domain representations of the downmix signal, the first frequency-domain representation of the residual signal and a complex prediction coefficient (a) encoded in a bit stream signal received by the decoder system;
wherein each spectral component represents a range of frequencies, and wherein each of the first spectral components of the side signal is determined from spectral components of the downmix signal and the residual signal representing the same range of frequencies as the first spectral component of the side signal; anda sum-and-difference stage for computing the stereo signal on the basis of the first frequency-domain representation of the downmix signal and the side signal, wherein the upmix stage is further operable in a pass-through mode, in which said downmix and residual signals are supplied to the sum-and-difference stage directly. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A decoding method for providing a stereo signal by complex prediction stereo coding, the method comprising the steps of:
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receiving first frequency-domain representations of a downmix signal (M) and a residual signal (D), each of the first frequency-domain representations comprising first spectral components representing spectral content of the corresponding signal expressed in a first subspace of a multidimensional space; receiving a control signal; and responsive to the value of said control signal; (a) upmixing said downmix and residual signals, using an upmix stage, to obtain said stereo signal, by performing the sub-steps of; computing a second frequency-domain representation of the downmix signal based on the first frequency-domain representation thereof, the second frequency-domain representation comprising second spectral components representing spectral content of the signal expressed in a second subspace of the multidimensional space that includes a portion of the multidimensional space not included in the first subspace, wherein computing a second frequency-domain representation of the downmix signal includes determining the second spectral components of the downmix signal by applying a Finite Impulse Reponse (FIR) filter to the first spectral components of the downmix signal; computing a first frequency-domain representation of a side signal (S), the first frequency-domain representation of the side signal (S) comprising first spectral components representing spectral content of the side signal expressed in the first subspace of the multidimensional space, on the basis of the first and second frequency-domain representations of the downmix signal, the first frequency-domain representation of the residual signal and a complex prediction coefficient (a) encoded in a bit stream signal;
wherein each spectral component represents a range of frequencies, and wherein each of the first spectral components of the side signal is determined from spectral components of the downmix signal and the residual signal representing the same range of frequencies as the first spectral component of the side signal; andcomputing said stereo signal by applying a sum-and-difference transform to the first frequency-domain representation of the downmix signal and the side signal, or (b) suspending upmixing. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification