Complex exponential modulated filter bank for high frequency reconstruction or parametric stereo
First Claim
1. A signal processing device for filtering an audio signal, the signal processing device comprising:
- an analysis filter bank that receives real valued time domain input audio samples and generates complex-valued subband samples;
a phase shifter that shifts a phase of the complex-valued subband samples by an amount;
a high frequency reconstructor or parametric stereo processor that generates modified complex-valued subband samples;
a phase shifter that unshifts a phase of the modified complex-valued subband samples by the amount; and
a synthesis filter bank that receives the modified complex-valued subband samples and generates time domain output audio samples,wherein the analysis filter bank comprises analysis filters (hk(n)) and the synthesis filter bank comprises synthesis filters (fk(n)) that are complex exponential modulated versions of a prototype filter (p0(n)) according to;
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Abstract
An apparatus and method are disclosed for filtering and performing high frequency reconstruction of an audio signal. The apparatus includes an analysis filter bank, a phase shifter, a high frequency reconstructor, and a synthesis filter bank. The analysis filterbank receives real-valued time domain input audio samples and generates complex valued subband samples. The phase shifter shifts a phase of the complex-valued subband samples by an arbitrary amount. The high frequency reconstructor modifies at least some of the complex valued subband samples. A phase shifter unshifts a phase of the modified complex-valued subband samples by the arbitrary amount. The synthesis filter bank receives the modified complex valued subband samples and generates time domain output audio samples. The analysis filter bank comprises analysis filters that are complex exponential modulated versions of a prototype filter with an arbitrary phase shift.
10 Citations
11 Claims
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1. A signal processing device for filtering an audio signal, the signal processing device comprising:
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an analysis filter bank that receives real valued time domain input audio samples and generates complex-valued subband samples; a phase shifter that shifts a phase of the complex-valued subband samples by an amount; a high frequency reconstructor or parametric stereo processor that generates modified complex-valued subband samples; a phase shifter that unshifts a phase of the modified complex-valued subband samples by the amount; and a synthesis filter bank that receives the modified complex-valued subband samples and generates time domain output audio samples, wherein the analysis filter bank comprises analysis filters (hk(n)) and the synthesis filter bank comprises synthesis filters (fk(n)) that are complex exponential modulated versions of a prototype filter (p0(n)) according to; - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method performed by an signal processing device for filtering an audio signal, the method comprising:
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receiving real-valued time domain input audio samples; filtering the real-valued time domain input audio samples with an analysis filter bank to generate complex valued subband samples; shifting a phase of the complex-valued subband samples by an amount; generating modified complex valued subband samples through a high frequency reconstruction process or a parametric stereo process; unshifting a phase of the modified complex-valued subband samples by the amount; receiving the modified complex valued subband samples; filtering the modified complex valued subband samples with a synthesis filter bank to generate time domain output audio samples, wherein the analysis filter bank comprises analysis filters (hk(n)) and the synthesis filter bank comprises synthesis filters (fk(n)) that are complex exponential modulated versions of a prototype filter (p0(n)) according to; - View Dependent Claims (11)
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Specification