_ak_reverb_estimation_8h

Wwise SDK 2021.1.14

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 released in source code form as part of the SDK installer package.

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 Version: v2021.1.14  Build: 6590

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 /// \file 

 /// Reverb parameter estimation.

 #pragma once

 #include <AK/SoundEngine/Common/AkTypes.h>

 #include <AK/SpatialAudio/Common/AkSpatialAudio.h>

 #include <AK/SoundEngine/Common/AkVirtualAcoustics.h>

 namespace AK {

 namespace SpatialAudio {

 /// Audiokinetic reverb estimation namespace

 namespace ReverbEstimation

 {

     ////////////////////////////////////////////////////////////////////////

     /// @name Reverb estimation. 

     /// These functions can be used to estimate the reverb parameters of a physical environment, using its volume and surface area

     //@{

     /// This is used to estimate the line of best fit through the absorption values of an Acoustic Texture.

     /// This value is what's known as the HFDamping.

     /// return Gradient of line of best fit through y = mx + c.

     float CalculateSlope(const AkAcousticTexture& texture)

     {

         // constants for the mean and standard deviation of the acoustic texture indices 0,1,2,3

         const float meanX = 1.5f;

         const float sdX = 1.11803399;

         const int N = 4;

         float meanY = (texture.fAbsorptionLow + texture.fAbsorptionMidLow + texture.fAbsorptionMidHigh + texture.fAbsorptionHigh) / (float)N;

         float absorptions[4] = { texture.fAbsorptionLow, texture.fAbsorptionMidLow, texture.fAbsorptionMidHigh, texture.fAbsorptionHigh };

         float sdY = 0.0f;

         float meanDiffDotProd = 0.0f;

         for (int i = 0; i < N; ++i)

         {

             const float yMeanDiff = absorptions[i] - meanY;

             const float xMeanDiff = (float)i - meanX;

             meanDiffDotProd += yMeanDiff * xMeanDiff;

             sdY += yMeanDiff * yMeanDiff;

         }

         if (sdY == 0.0f)

             return 0.0f;

         sdY = sqrtf(sdY / (float)N);

         const float correlationCoeff = (1.0f / (N - 1.0f)) * (meanDiffDotProd / (sdY * sdX));

         return correlationCoeff * (sdY / sdX);

     }

     /// Calculate average absorption values using each of the textures in in_textures, weighted by their corresponding surface area.

     void GetAverageAbsorptionValues(AkAcousticTexture* in_textures, float* in_surfaceAreas, int in_numTextures, AkAcousticTexture& out_average)

     {

         float surfaceArea = 0.0f;

         float totalSurfaceArea = 0.0f;

         out_average.fAbsorptionLow = 0.0f;

         out_average.fAbsorptionMidLow = 0.0f;

         out_average.fAbsorptionMidHigh = 0.0f;

         out_average.fAbsorptionHigh = 0.0f;

         for (int textureIndex = 0; textureIndex < in_numTextures; ++textureIndex)

         {

             AkAcousticTexture& texture = in_textures[textureIndex];

             surfaceArea = in_surfaceAreas[textureIndex];

             out_average.fAbsorptionLow += texture.fAbsorptionLow * surfaceArea;

             out_average.fAbsorptionMidLow += texture.fAbsorptionMidLow * surfaceArea;

             out_average.fAbsorptionMidHigh += texture.fAbsorptionMidHigh * surfaceArea;

             out_average.fAbsorptionHigh += texture.fAbsorptionHigh * surfaceArea;

             totalSurfaceArea += surfaceArea;

         }

         AKASSERT(totalSurfaceArea > 0.0f);

         out_average.fAbsorptionLow = out_average.fAbsorptionLow / totalSurfaceArea;

         out_average.fAbsorptionMidLow = out_average.fAbsorptionMidLow / totalSurfaceArea;

         out_average.fAbsorptionMidHigh = out_average.fAbsorptionMidHigh / totalSurfaceArea;

         out_average.fAbsorptionHigh = out_average.fAbsorptionHigh / totalSurfaceArea;

     }

     /// Estimate the time taken (in seconds) for the sound reverberation in a physical environment to decay by 60 dB.

     /// This is estimated using the Sabine equation. The T60 decay time can be used to drive the decay parameter of a reverb effect.

     AK_EXTERNAPIFUNC(AKRESULT, EstimateT60Decay)(

         AkReal32 in_volumeCubicMeters,              ///< The volume (in cubic meters) of the physical environment. 0 volume or negative volume will give a decay estimate of 0.

         AkReal32 in_surfaceAreaSquaredMeters,       ///< The surface area (in squared meters) of the physical environment. Must be >= AK_SA_MIN_ENVIRONMENT_SURFACE_AREA

         AkReal32 in_environmentAverageAbsorption,   ///< The average absorption amount of the surfaces in the environment. Must be between AK_SA_MIN_ENVIRONMENT_ABSORPTION and 1.

         AkReal32& out_decayEstimate                 ///< Returns the time taken (in seconds) for the reverberation to decay bu 60 dB.

         )

     {

         if (in_volumeCubicMeters <= 0.0f)

         {

             out_decayEstimate = 0.0f;

             return AKRESULT::AK_Success;

         }

         if (in_surfaceAreaSquaredMeters < AK_SA_MIN_ENVIRONMENT_SURFACE_AREA)

         {

             AKASSERT(false && "AK::SpatialAudio::ReverbEstimation::EstimateT60Decay: Invalid surface area. in_SurfaceAreaSquaredMeters Must be >= AK_SA_MIN_ENVIRONMENT_SURFACE_AREA");

             return AKRESULT::AK_Fail;

         }

         if (in_environmentAverageAbsorption < AK_SA_MIN_ENVIRONMENT_ABSORPTION || in_environmentAverageAbsorption > 1.0f)

         {

             AKASSERT(false && "AK::SpatialAudio::ReverbEstimation::EstimateT60Decay: Invalid absorption value. in_EnvironmentAverageAbsorption Must be between AK_SA_MIN_ENVIRONMENT_ABSORPTION and 1");

             return AKRESULT::AK_Fail;

         }

         // The Sabine equation.

         out_decayEstimate = (0.161f * in_volumeCubicMeters) / (in_surfaceAreaSquaredMeters * in_environmentAverageAbsorption);

         return AKRESULT::AK_Success;

     }

     /// Estimate the time taken (in milliseconds) for the first reflection to reach the listener.

     /// This assumes the emitter and listener are both positioned in the centre of the environment.

     AK_EXTERNAPIFUNC(AKRESULT, EstimateTimeToFirstReflection)(

         AkVector in_environmentExtentMeters,    ///< Defines the dimensions of the environment (in meters) relative to the center; all components must be positive numbers.

         AkReal32& out_timeToFirstReflectionMs,  ///< Returns the time taken (in milliseconds) for the first reflection to reach the listener.

         AkReal32 in_speedOfSound = 343.0f       ///< Defaults to 343.0 - the speed of sound in dry air. Must be > 0.

         )

     {

         if (in_speedOfSound <= 0.0f)

         {

             AKASSERT(false && "AK::SpatialAudio::ReverbEstimation::EstimateTimeToFirstReflection: Invalid speed of sound. in_speedOfSound must be greater than 0.");

             return AKRESULT::AK_Fail;

         }

         if (in_environmentExtentMeters.X < 0.0f || in_environmentExtentMeters.Y < 0.0f || in_environmentExtentMeters.Z < 0.0f)

         {

             AKASSERT(false && "AK::SpatialAudio::ReverbEstimation::EstimateTimeToFirstReflection: Invalid extent. All components must be positive numbers.");

             return AKRESULT::AK_Fail;

         }

         const float minDimension = AkMin(AkMin(in_environmentExtentMeters.X, in_environmentExtentMeters.Y), in_environmentExtentMeters.Z);

         out_timeToFirstReflectionMs = minDimension / in_speedOfSound;

         return AKRESULT::AK_Success;

     }

     /// Estimate the high frequency damping from a collection of AkAcousticTextures and corresponding surface areas. 

     /// The high frequency damping is a measure of how much high frequencies are dampened compared to low frequencies. > 0 indicates more high frequency damping than low frequency damping. < 0 indicates more low frequency damping than high frequency damping. 0 indicates uniform damping.

     /// The average absorption values are calculated using each of the textures in the collection, weighted by their corresponding surface area.

     /// The HFDamping is then calculated as the line-of-best-fit through the average absorption values.

     AK_EXTERNAPIFUNC(AKRESULT, EstimateHFDamping)(

         AkAcousticTexture* in_textures, ///< A collection of AkAcousticTexture structs from which to calculate the average high frequency damping.

         float* in_surfaceAreas,         ///< Surface area values for each of the textures in in_textures.

         int in_numTextures,             ///< The number of textures in in_textures (and the number of surface area values in in_surfaceAreas).

         AkReal32& out_hfDamping         ///< Returns the high frequency damping value. > 0 indicates more high frequency damping than low frequency damping. < 0 indicates more low frequency damping than high frequency damping. 0 indicates uniform damping.

         )

     {

         if (in_textures == nullptr || in_surfaceAreas == nullptr || in_numTextures == 0)

         {

             out_hfDamping = 0.0f;

             return AK_Success;

         }

         AkAcousticTexture averageAbsorptionValues;

         GetAverageAbsorptionValues(in_textures, in_surfaceAreas, in_numTextures, averageAbsorptionValues);

         out_hfDamping = CalculateSlope(averageAbsorptionValues);

         return AK_Success;

     }

     //@}

 }

 }

 }

AkMin

#define AkMin(x1, x2)

Definition: AkPlatformFuncs.h:94

AkReal32

float AkReal32

32-bit floating point

Definition: AkTypes.h:70

AK::SpatialAudio::ReverbEstimation::EstimateHFDamping

AKSOUNDENGINE_API AKRESULT EstimateHFDamping(AkAcousticTexture *in_textures, float *in_surfaceAreas, int in_numTextures, AkReal32 &out_hfDamping)

Definition: AkReverbEstimation.h:158

Audiokinetic namespace

Definition: AkWwiseSDKVersion.cs:32

AK_Fail

@ AK_Fail

The operation failed.

Definition: AkTypes.h:135

AkAcousticTexture

Definition: AkVirtualAcoustics.h:34

AK_EXTERNAPIFUNC

#define AK_EXTERNAPIFUNC(_type, _name)

Definition: AkSoundEngineExport.h:78

AKRESULT

Standard function call result.

Definition: AkTypes.h:132

AkAcousticTexture::fAbsorptionHigh

AkReal32 fAbsorptionHigh

Definition: AkVirtualAcoustics.h:70

AkAcousticTexture::fAbsorptionMidHigh

AkReal32 fAbsorptionMidHigh

Definition: AkVirtualAcoustics.h:69

AK::SpatialAudio::ReverbEstimation::EstimateT60Decay

AKSOUNDENGINE_API AKRESULT EstimateT60Decay(AkReal32 in_volumeCubicMeters, AkReal32 in_surfaceAreaSquaredMeters, AkReal32 in_environmentAverageAbsorption, AkReal32 &out_decayEstimate)

Definition: AkReverbEstimation.h:104

AK_Success

@ AK_Success

The operation was successful.

Definition: AkTypes.h:134

AK::SpatialAudio::ReverbEstimation::EstimateTimeToFirstReflection

AKSOUNDENGINE_API AKRESULT EstimateTimeToFirstReflection(AkVector in_environmentExtentMeters, AkReal32 &out_timeToFirstReflectionMs, AkReal32 in_speedOfSound=343.0f)

Definition: AkReverbEstimation.h:133

AK_SA_MIN_ENVIRONMENT_SURFACE_AREA

#define AK_SA_MIN_ENVIRONMENT_SURFACE_AREA

Definition: AkSpatialAudioTypes.h:55

AkVector::Y

AkReal32 Y

Y Position

Definition: AkTypes.h:340

AK::SpatialAudio::ReverbEstimation::CalculateSlope

float CalculateSlope(const AkAcousticTexture &texture)

Definition: AkReverbEstimation.h:51

AkVector::X