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Wwise SDK 2022.1.12
AkReverbEstimation.h
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26 
27 /// \file
28 /// Reverb parameter estimation.
29 
30 #pragma once
31 
32 #include <AK/SoundEngine/Common/AkTypes.h>
33 #include <AK/SpatialAudio/Common/AkSpatialAudio.h>
34 #include <AK/SoundEngine/Common/AkVirtualAcoustics.h>
35 
36 namespace AK {
37 namespace SpatialAudio {
38 
39 /// Audiokinetic reverb estimation namespace
40 namespace ReverbEstimation
41 {
42  ////////////////////////////////////////////////////////////////////////
43  /// @name Reverb estimation.
44  /// These functions can be used to estimate the reverb parameters of a physical environment, using its volume and surface area
45  //@{
46 
47  /// This is used to estimate the line of best fit through the absorption values of an Acoustic Texture.
48  /// This value is what's known as the HFDamping.
49  /// return Gradient of line of best fit through y = mx + c.
50  float CalculateSlope(const AkAcousticTexture& texture)
51  {
52  // constants for the mean and standard deviation of the acoustic texture indices 0,1,2,3
53  const float meanX = 1.5f;
54  const float sdX = 1.11803399;
55 
56  const int N = 4;
57  float meanY = (texture.fAbsorptionLow + texture.fAbsorptionMidLow + texture.fAbsorptionMidHigh + texture.fAbsorptionHigh) / (float)N;
58  float absorptions[4] = { texture.fAbsorptionLow, texture.fAbsorptionMidLow, texture.fAbsorptionMidHigh, texture.fAbsorptionHigh };
59  float sdY = 0.0f;
60  float meanDiffDotProd = 0.0f;
61  for (int i = 0; i < N; ++i)
62  {
63  const float yMeanDiff = absorptions[i] - meanY;
64  const float xMeanDiff = (float)i - meanX;
65  meanDiffDotProd += yMeanDiff * xMeanDiff;
66  sdY += yMeanDiff * yMeanDiff;
67  }
68  if (sdY == 0.0f)
69  return 0.0f;
70  sdY = sqrtf(sdY / (float)N);
71  const float correlationCoeff = (1.0f / (N - 1.0f)) * (meanDiffDotProd / (sdY * sdX));
72  return correlationCoeff * (sdY / sdX);
73  }
74 
75  /// Calculate average absorption values using each of the textures in in_textures, weighted by their corresponding surface area.
76  void GetAverageAbsorptionValues(AkAcousticTexture* in_textures, float* in_surfaceAreas, int in_numTextures, AkAcousticTexture& out_average)
77  {
78  float surfaceArea = 0.0f;
79  float totalSurfaceArea = 0.0f;
80  out_average.fAbsorptionLow = 0.0f;
81  out_average.fAbsorptionMidLow = 0.0f;
82  out_average.fAbsorptionMidHigh = 0.0f;
83  out_average.fAbsorptionHigh = 0.0f;
84  for (int textureIndex = 0; textureIndex < in_numTextures; ++textureIndex)
85  {
86  AkAcousticTexture& texture = in_textures[textureIndex];
87  surfaceArea = in_surfaceAreas[textureIndex];
88  out_average.fAbsorptionLow += texture.fAbsorptionLow * surfaceArea;
89  out_average.fAbsorptionMidLow += texture.fAbsorptionMidLow * surfaceArea;
90  out_average.fAbsorptionMidHigh += texture.fAbsorptionMidHigh * surfaceArea;
91  out_average.fAbsorptionHigh += texture.fAbsorptionHigh * surfaceArea;
92  totalSurfaceArea += surfaceArea;
93  }
94  if (totalSurfaceArea > 0.0f)
95  {
96  out_average.fAbsorptionLow = out_average.fAbsorptionLow / totalSurfaceArea;
97  out_average.fAbsorptionMidLow = out_average.fAbsorptionMidLow / totalSurfaceArea;
98  out_average.fAbsorptionMidHigh = out_average.fAbsorptionMidHigh / totalSurfaceArea;
99  out_average.fAbsorptionHigh = out_average.fAbsorptionHigh / totalSurfaceArea;
100  }
101  }
102 
103  /// Estimate the time taken (in seconds) for the sound reverberation in a physical environment to decay by 60 dB.
104  /// This is estimated using the Sabine equation. The T60 decay time can be used to drive the decay parameter of a reverb effect.
105  AK_EXTERNAPIFUNC(AKRESULT, EstimateT60Decay)(
106  AkReal32 in_volumeCubicMeters, ///< The volume (in cubic meters) of the physical environment. 0 volume or negative volume will give a decay estimate of 0.
107  AkReal32 in_surfaceAreaSquaredMeters, ///< The surface area (in squared meters) of the physical environment. Must be >= AK_SA_MIN_ENVIRONMENT_SURFACE_AREA
108  AkReal32 in_environmentAverageAbsorption, ///< The average absorption amount of the surfaces in the environment. Must be between AK_SA_MIN_ENVIRONMENT_ABSORPTION and 1.
109  AkReal32& out_decayEstimate ///< Returns the time taken (in seconds) for the reverberation to decay bu 60 dB.
110  )
111  {
112  if (in_volumeCubicMeters <= 0.0f)
113  {
114  out_decayEstimate = 0.0f;
115  return AKRESULT::AK_Success;
116  }
117  if (in_surfaceAreaSquaredMeters < AK_SA_MIN_ENVIRONMENT_SURFACE_AREA)
118  {
119  AKASSERT(false && "AK::SpatialAudio::ReverbEstimation::EstimateT60Decay: Invalid surface area. in_SurfaceAreaSquaredMeters Must be >= AK_SA_MIN_ENVIRONMENT_SURFACE_AREA");
120  return AKRESULT::AK_Fail;
121  }
122  if (in_environmentAverageAbsorption < AK_SA_MIN_ENVIRONMENT_ABSORPTION || in_environmentAverageAbsorption > 1.0f)
123  {
124  AKASSERT(false && "AK::SpatialAudio::ReverbEstimation::EstimateT60Decay: Invalid absorption value. in_EnvironmentAverageAbsorption Must be between AK_SA_MIN_ENVIRONMENT_ABSORPTION and 1");
125  return AKRESULT::AK_Fail;
126  }
127  // The Sabine equation.
128  out_decayEstimate = (0.161f * in_volumeCubicMeters) / (in_surfaceAreaSquaredMeters * in_environmentAverageAbsorption);
129  return AKRESULT::AK_Success;
130  }
131 
132  /// Estimate the time taken (in milliseconds) for the first reflection to reach the listener.
133  /// This assumes the emitter and listener are both positioned in the centre of the environment.
134  AK_EXTERNAPIFUNC(AKRESULT, EstimateTimeToFirstReflection)(
135  AkVector in_environmentExtentMeters, ///< Defines the dimensions of the environment (in meters) relative to the center; all components must be positive numbers.
136  AkReal32& out_timeToFirstReflectionMs, ///< Returns the time taken (in milliseconds) for the first reflection to reach the listener.
137  AkReal32 in_speedOfSound = 343.0f ///< Defaults to 343.0 - the speed of sound in dry air. Must be > 0.
138  )
139  {
140  if (in_speedOfSound <= 0.0f)
141  {
142  AKASSERT(false && "AK::SpatialAudio::ReverbEstimation::EstimateTimeToFirstReflection: Invalid speed of sound. in_speedOfSound must be greater than 0.");
143  return AKRESULT::AK_Fail;
144  }
145  if (in_environmentExtentMeters.X < 0.0f || in_environmentExtentMeters.Y < 0.0f || in_environmentExtentMeters.Z < 0.0f)
146  {
147  AKASSERT(false && "AK::SpatialAudio::ReverbEstimation::EstimateTimeToFirstReflection: Invalid extent. All components must be positive numbers.");
148  return AKRESULT::AK_Fail;
149  }
150  const float minDimension = AkMin(AkMin(in_environmentExtentMeters.X, in_environmentExtentMeters.Y), in_environmentExtentMeters.Z);
151  out_timeToFirstReflectionMs = (minDimension / in_speedOfSound) * 1000.0f;
152  return AKRESULT::AK_Success;
153  }
154 
155  /// Estimate the high frequency damping from a collection of AkAcousticTextures and corresponding surface areas.
156  /// 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.
157  /// The average absorption values are calculated using each of the textures in the collection, weighted by their corresponding surface area.
158  /// The HFDamping is then calculated as the line-of-best-fit through the average absorption values.
159  AK_EXTERNAPIFUNC(AKRESULT, EstimateHFDamping)(
160  AkAcousticTexture* in_textures, ///< A collection of AkAcousticTexture structs from which to calculate the average high frequency damping.
161  float* in_surfaceAreas, ///< Surface area values for each of the textures in in_textures.
162  int in_numTextures, ///< The number of textures in in_textures (and the number of surface area values in in_surfaceAreas).
163  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.
164  )
165  {
166  if (in_textures == nullptr || in_surfaceAreas == nullptr || in_numTextures == 0)
167  {
168  out_hfDamping = 0.0f;
169  return AK_Success;
170  }
171  AkAcousticTexture averageAbsorptionValues;
172  GetAverageAbsorptionValues(in_textures, in_surfaceAreas, in_numTextures, averageAbsorptionValues);
173  out_hfDamping = CalculateSlope(averageAbsorptionValues);
174  return AK_Success;
175  }
176 
177  //@}
178 }
179 }
180 }
AkMin
#define AkMin(x1, x2)
Definition: AkPlatformFuncs.h:94
AK::SpatialAudio::ReverbEstimation::EstimateHFDamping
AKSOUNDENGINE_API AKRESULT EstimateHFDamping(AkAcousticTexture *in_textures, float *in_surfaceAreas, int in_numTextures, AkReal32 &out_hfDamping)
Definition: AkReverbEstimation.h:159
AK
Audiokinetic namespace.
Definition: AkWwiseSDKVersion.cs:31
AK_Fail
@ AK_Fail
The operation failed.
Definition: AkTypes.h:202
AK_EXTERNAPIFUNC
#define AK_EXTERNAPIFUNC(_type, _name)
Definition: AkSoundEngineExport.h:81
AKRESULT
AKRESULT
Standard function call result.
Definition: AkTypes.h:199
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:201
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:50
AkVector::Y
AkReal32 Y
Y Position.
Definition: AkTypes.h:468
AK::SpatialAudio::ReverbEstimation::CalculateSlope
float CalculateSlope(const AkAcousticTexture &texture)
Definition: AkReverbEstimation.h:50
AkVector::X
AkReal32 X
X Position.
Definition: AkTypes.h:467
AKASSERT
#define AKASSERT(Condition)
Definition: AkAssert.h:67
AkVector::Z
AkReal32 Z
Z Position.
Definition: AkTypes.h:469
AK::SpatialAudio::ReverbEstimation::GetAverageAbsorptionValues
void GetAverageAbsorptionValues(AkAcousticTexture *in_textures, float *in_surfaceAreas, int in_numTextures, AkAcousticTexture &out_average)
Calculate average absorption values using each of the textures in in_textures, weighted by their corr...
Definition: AkReverbEstimation.h:76
AkVector
3D vector for some operations in 3D space. Typically intended only for localized calculations due to ...
Definition: AkTypes.h:425

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