Sample rate converter with automatic anti-aliasing filter
AssigneeMicrosoft Technology Licensing, LLC
InventorThomas Craig Savell
Life of this patent
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Abstract
The subject disclosure is directed towards dynamically computing anti-aliasing filter coefficients for sample rate conversion in digital audio. In one aspect, for each input-to-output sampling rate ratio (pitch) obtained, anti-aliasing filter coefficients are interpolated based upon the pitch (e.g., using the fractional part of the ratio) from two filters (coefficient sets) selected based upon the pitch (e.g., using the integer part of the ratio). The interpolation provides for fine-grained cutoff frequencies, and by re-computation for each pitch, smooth anti-aliasing with dynamically changing ratios.
Claims1
A method comprising:
- obtaining a pitch corresponding to an input audio sampling rate of an input sample and an output audio rate for a sample rate converted sample;
- selecting a filter comprising a set of coefficient values based upon the pitch;
- performing one subphase interpolation between a subphase identified from a phase and a subphase adjacent thereto to obtain one subphase interpolation result;
- performing another subphase interpolation between a second subphase identified from the phase and a second subphase adjacent thereto to obtain another subphase interpolation result;
- and
- performing an interpolation between the one subphase interpolation result and the other subphase interpolation result to obtain a resultant set of pitch-based coefficient values.
Dependencies are inferred from the claim text.