731e52c440
Bundle libOpenMPT as a dynamic framework, which should be safe once again, now that there is only one version to bundle. Also, now it is using the versions of libvorbisfile and libmpg123 that are bundled with the player, instead of compiling minimp3 and stbvorbis. Signed-off-by: Christopher Snowhill <kode54@gmail.com>
82 lines
2.5 KiB
C++
82 lines
2.5 KiB
C++
/*
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* WindowedFIR.h
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* -------------
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* Purpose: FIR resampling code
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* Notes : (currently none)
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* Authors: OpenMPT Devs
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* ModPlug-XMMS Devs
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* The OpenMPT source code is released under the BSD license. Read LICENSE for more details.
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*/
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#pragma once
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#include "openmpt/all/BuildSettings.hpp"
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#include "Mixer.h"
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OPENMPT_NAMESPACE_BEGIN
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/*
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------------------------------------------------------------------------------------------------
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fir interpolation doc,
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(derived from "an engineer's guide to fir digital filters", n.j. loy)
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calculate coefficients for ideal lowpass filter (with cutoff = fc in 0..1 (mapped to 0..nyquist))
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c[-N..N] = (i==0) ? fc : sin(fc*pi*i)/(pi*i)
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then apply selected window to coefficients
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c[-N..N] *= w(0..N)
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with n in 2*N and w(n) being a window function (see loy)
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then calculate gain and scale filter coefs to have unity gain.
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------------------------------------------------------------------------------------------------
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*/
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#ifdef MPT_INTMIXER
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// quantizer scale of window coefs - only required for integer mixing
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inline constexpr int WFIR_QUANTBITS = 15;
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inline constexpr double WFIR_QUANTSCALE = 1 << WFIR_QUANTBITS;
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inline constexpr int WFIR_8SHIFT = (WFIR_QUANTBITS - 8);
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inline constexpr int WFIR_16BITSHIFT = (WFIR_QUANTBITS);
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using WFIR_TYPE = int16;
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#else
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using WFIR_TYPE = mixsample_t;
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#endif // INTMIXER
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// log2(number)-1 of precalculated taps range is [4..12]
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inline constexpr int WFIR_FRACBITS = 12; //10
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inline constexpr int WFIR_LUTLEN = ((1 << (WFIR_FRACBITS + 1)) + 1);
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// number of samples in window
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inline constexpr int WFIR_LOG2WIDTH = 3;
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inline constexpr int WFIR_WIDTH = (1 << WFIR_LOG2WIDTH);
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// cutoff (1.0 == pi/2)
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// wfir type
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enum WFIRType
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{
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WFIR_HANN = 0, // Hann
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WFIR_HAMMING = 1, // Hamming
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WFIR_BLACKMANEXACT = 2, // Blackman Exact
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WFIR_BLACKMAN3T61 = 3, // Blackman 3-Tap 61
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WFIR_BLACKMAN3T67 = 4, // Blackman 3-Tap 67
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WFIR_BLACKMAN4T92 = 5, // Blackman-Harris
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WFIR_BLACKMAN4T74 = 6, // Blackman 4-Tap 74
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WFIR_KAISER4T = 7, // Kaiser a=7.5
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};
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// fir interpolation
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inline constexpr int WFIR_FRACSHIFT = (16 - (WFIR_FRACBITS + 1 + WFIR_LOG2WIDTH));
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inline constexpr int WFIR_FRACMASK = ((((1 << (17 - WFIR_FRACSHIFT)) - 1) & ~(WFIR_WIDTH - 1)));
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inline constexpr int WFIR_FRACHALVE = (1 << (16 - (WFIR_FRACBITS + 2)));
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class CWindowedFIR
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{
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private:
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double coef(int,double,double,int,int);
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public:
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void InitTable(double WFIRCutoff, uint8 WFIRType);
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WFIR_TYPE lut[WFIR_LUTLEN * WFIR_WIDTH];
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};
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OPENMPT_NAMESPACE_END
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