_ak_reverb_estimation_8h

Wwise SDK 2024.1.0

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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 = 1.11803399f;
  
         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;
         }
         if (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) * 1000.0f;
         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. 
     /// The value is comprised between -1 and 1. A 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.
     /// 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(AkReal32, 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).
         )
     {
         if (in_textures == nullptr || in_surfaceAreas == nullptr || in_numTextures == 0)
         {
             return 0.0f;
         }
         AkAcousticTexture averageAbsorptionValues;
         GetAverageAbsorptionValues(in_textures, in_surfaceAreas, in_numTextures, averageAbsorptionValues);
         return CalculateSlope(averageAbsorptionValues) * 2.f; // Multiply by 2 so that the Hf Damping value is between -1 and 1.
     }
  
     //@}
 }
 }
 }

AkMin

#define AkMin(x1, x2)

Definition: AkPlatformFuncs.h:90

Definition of data structures for AkAudioObject.

Definition: AkWwiseSDKVersion.cs:31

AK_Fail

@ AK_Fail

The operation failed.

Definition: AkTypes.h:137

AkAcousticTexture

Definition: AkVirtualAcoustics.h:33

AK_EXTERNAPIFUNC

#define AK_EXTERNAPIFUNC(_type, _name)

Definition: AkSoundEngineExport.h:81

AKRESULT

Standard function call result.

Definition: AkTypes.h:134

AK::SpatialAudio::ReverbEstimation::EstimateHFDamping

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

Definition: AkReverbEstimation.h:160

AkAcousticTexture::fAbsorptionHigh

AkReal32 fAbsorptionHigh

Definition: AkVirtualAcoustics.h:79

AkAcousticTexture::fAbsorptionMidHigh

AkReal32 fAbsorptionMidHigh

Definition: AkVirtualAcoustics.h:78

AK::SpatialAudio::ReverbEstimation::EstimateT60Decay

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

Definition: AkReverbEstimation.h:105

AkReal32

float AkReal32

32-bit floating point

Definition: AkNumeralTypes.h:46

AK_Success

@ AK_Success

The operation was successful.

Definition: AkTypes.h:136

AK::SpatialAudio::ReverbEstimation::EstimateTimeToFirstReflection

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

Definition: AkReverbEstimation.h:134

AK_SA_MIN_ENVIRONMENT_SURFACE_AREA

#define AK_SA_MIN_ENVIRONMENT_SURFACE_AREA

Definition: AkSpatialAudioTypes.h:51

AkVector::Y

AkReal32 Y

Y Position.

Definition: AkTypes.h:423

AK::SpatialAudio::ReverbEstimation::CalculateSlope

float CalculateSlope(const AkAcousticTexture &texture)

Definition: AkReverbEstimation.h:50

AkVector::X