54 lines
1.5 KiB
C++
54 lines
1.5 KiB
C++
#ifndef UHJFILTER_H
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#define UHJFILTER_H
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#include <array>
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#include "alcmain.h"
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#include "almalloc.h"
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/* Encoding 2-channel UHJ from B-Format is done as:
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*
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* S = 0.9396926*W + 0.1855740*X
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* D = j(-0.3420201*W + 0.5098604*X) + 0.6554516*Y
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*
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* Left = (S + D)/2.0
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* Right = (S - D)/2.0
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*
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* where j is a wide-band +90 degree phase shift.
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*
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* The phase shift is done using a FIR filter derived from an FFT'd impulse
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* with the desired shift.
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*/
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struct Uhj2Encoder {
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/* A particular property of the filter allows it to cover nearly twice its
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* length, so the filter size is also the effective delay (despite being
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* center-aligned).
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*/
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constexpr static size_t sFilterSize{128};
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/* Delays for the unfiltered signal. */
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alignas(16) std::array<float,sFilterSize> mMidDelay{};
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alignas(16) std::array<float,sFilterSize> mSideDelay{};
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/* History for the FIR filter. */
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alignas(16) std::array<float,sFilterSize*2 - 1> mSideHistory{};
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alignas(16) std::array<float,BUFFERSIZE + sFilterSize*2> mTemp{};
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alignas(16) std::array<float,BUFFERSIZE> mMid{};
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alignas(16) std::array<float,BUFFERSIZE> mSide{};
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/**
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* Encodes a 2-channel UHJ (stereo-compatible) signal from a B-Format input
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* signal. The input must use FuMa channel ordering and scaling.
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*/
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void encode(FloatBufferLine &LeftOut, FloatBufferLine &RightOut,
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const FloatBufferLine *InSamples, const size_t SamplesToDo);
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DEF_NEWDEL(Uhj2Encoder)
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};
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#endif /* UHJFILTER_H */
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