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#rb aaron.mcleran phil.popp #jira UEAU-720 #ROBOMERGE-SOURCE: CL 15619889 in //UE5/Release-5.0-EarlyAccess/... #ROBOMERGE-BOT: STARSHIP (Release-5.0-EarlyAccess -> Main) (v777-15581079) [CL 15619902 by jimmy smith in ue5-main branch]
70 lines
1.8 KiB
C++
70 lines
1.8 KiB
C++
// Copyright Epic Games, Inc. All Rights Reserved.
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#include "DSP/Noise.h"
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#include "DSP/Dsp.h"
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#include "HAL/PlatformTime.h"
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namespace Audio
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{
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FWhiteNoise::FWhiteNoise(int32 InRandomSeed)
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: RandomStream{ InRandomSeed }
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{}
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FWhiteNoise::FWhiteNoise()
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: FWhiteNoise{ static_cast<int32>(FPlatformTime::Cycles()) }
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{}
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static const float DefaultFilterGain = Audio::ConvertToLinear(-3.f);
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FPinkNoise::FPinkNoise(int32 InRandomSeed)
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: Noise{ InRandomSeed }
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, X_Z{ 0,0,0,0 }
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, Y_Z{ 0,0.0,0 }
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, A0{ DefaultFilterGain }
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{
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static_assert(UE_ARRAY_COUNT(X_Z) == 4, "sizeof(X_Z)==4");
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static_assert(UE_ARRAY_COUNT(Y_Z) == 4, "sizeof(Y_Z)==4");
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}
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FPinkNoise::FPinkNoise()
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: FPinkNoise{static_cast<int32>(FPlatformTime::Cycles())}
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{}
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float FPinkNoise::Generate()
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{
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// Filter Coefficients based on:
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// https://ccrma.stanford.edu/~jos/sasp/Example_Synthesis_1_F_Noise.html
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static constexpr float A[4] { 1.0f, -2.494956002f,2.017265875f, -0.522189400f };
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static constexpr float B[4] { 0.049922035f,-0.095993537f,0.050612699f,-0.004408786f};
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static_assert(UE_ARRAY_COUNT(A) == UE_ARRAY_COUNT(X_Z), "A Coefficients and X need to be the same size");
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static_assert(UE_ARRAY_COUNT(B) == UE_ARRAY_COUNT(Y_Z), "B Coefficients and Y need to be the same size");
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X_Z[0] = Noise.Generate(); // Xn
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float Yn =
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A0 * X_Z[0] // a0 * (x) (inject non-const filter-gain A0 in here).
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+ A[1] * X_Z[1] // a1 * (x-1)
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+ A[2] * X_Z[2] // a2 * (x-2)
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+ A[3] * X_Z[3] // a3 * (x-3)
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- B[0] * Y_Z[0] // b1 * (y-1)
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- B[1] * Y_Z[1] // b2 * (y-2)
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- B[2] * Y_Z[2] // b3 * (y-3)
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- B[3] * Y_Z[3]; // b4 * (y-4)
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// Shuffle feed-forward state by one.
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X_Z[3] = X_Z[2];
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X_Z[2] = X_Z[1];
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X_Z[1] = X_Z[0];
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// Shuffle feed-back state by one.
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Y_Z[3] = Y_Z[2];
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Y_Z[2] = Y_Z[1];
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Y_Z[1] = Y_Z[0];
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Y_Z[0] = Yn;
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return Yn;
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}
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}
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