Directivity Extension

Version 52 (Nils Peters, 06/02/2009 05:28 pm)

1 1 Nils Peters
h1. Directivity Extension
2 1 Nils Peters
3 41 Nils Peters
* to describe radiation pattern of virtual sound sources 
4 51 Nils Peters
* Orientation of entity (Yaw, Pitch, Roll) towards a listener
5 51 Nils Peters
   
6 1 Nils Peters
7 22 Nils Peters
h1. Review
8 2 Nils Peters
9 51 Nils Peters
h2. [[Spatialisateur]] (aperture)
10 31 Nils Peters
11 39 Nils Peters
not written yet
12 39 Nils Peters
13 31 Nils Peters
h2. [[Space Unit Generator]]
14 41 Nils Peters
15 41 Nils Peters
Frequency independent source radiation pattern is defined through the @back@ parameter which sets the radiation gain between 0 and 1. in the opposite direction. The result is a radiation pattern in cardioid shape form.
16 31 Nils Peters
17 31 Nils Peters
!SUG.gif!
18 1 Nils Peters
19 40 Nils Peters
h2. [[jmod.sur.vimic~|ViMiC]]
20 32 Nils Peters
21 35 Nils Peters
The source directivity can be modeled through a frequency independent gain factor between 0 and 1. for each radiation angle to a 1º accuracy.     
22 35 Nils Peters
                                                                          
23 32 Nils Peters
!ViMiC.gif!
24 1 Nils Peters
25 1 Nils Peters
h2. AudioTwist
26 39 Nils Peters
27 39 Nils Peters
not written yet
28 1 Nils Peters
29 50 Nils Peters
h2. [[DIVA]] 
30 50 Nils Peters
31 50 Nils Peters
not written yet
32 50 Nils Peters
33 36 Nils Peters
h2. "OpenAL":http://connect.creativelabs.com/openal/default.aspx
34 1 Nils Peters
35 36 Nils Peters
??ability to simulate realistic directivity characteristics by either *specifying parametric filtering associated to radiation angles*, or *triplets of angle, frequency and attenuation*.??
36 36 Nils Peters
(Jean Marc Jot, "Scene Description Model and Rendering Engine for Interactive Virtual Acoustics", 120th AES Convention)
37 31 Nils Peters
38 36 Nils Peters
h2. "X3D":http://libx3d.sourceforge.net/ISO-IEC-19775-X3DAbstractSpecification/index.html Sound Node
39 1 Nils Peters
40 36 Nils Peters
* Inner ellipsoid defines a volume of space in which the maximum level of the sound is audible. Within this ellipsoid, the normalized sample data is scaled by the intensity field and there is no attenuation. The inner ellipsoid is defined by extending the direction vector through the location. The @minBack@ and @minFront@ fields specify distances behind and in front of the location along the direction vector respectively. The inner ellipsoid has one of its foci at location (the second focus is implicit) and intersects the direction vector at @minBack@ and @minFront@.
41 1 Nils Peters
42 36 Nils Peters
* Outer ellipsoid defines a volume of space that bounds the audibility of the sound. No sound can be heard outside of this outer ellipsoid. The outer ellipsoid is defined by extending the direction vector through the location. The @maxBack@ and @maxFront@ fields specify distances behind and in front of the location along the direction vector respectively. The outer ellipsoid has one of its foci at location (the second focus is implicit) and intersects the direction vector at @maxBack@ and @maxFront@.
43 36 Nils Peters
* The @minFront@, @maxFront@, @minBack@, and @maxBack@ fields are defined in local coordinates, and are ≥ zero.
44 36 Nils Peters
* @minBack@ ≤ @maxBack@
45 36 Nils Peters
* @minFront@ ≤ @maxFront@
46 36 Nils Peters
* Parameters are specified in the local coordinate system but the ellipsoids' geometry is affected by ancestors' transformations.
47 36 Nils Peters
* Between the two ellipsoids, there shall be a *linear attenuation ramp* in loudness, from 0 dB at the minimum ellipsoid to -20 dB at the maximum ellipsoid: *attenuation = -20 × (d' / d")* (*d'* is the distance along the location-to-viewer vector, measured from the transformed minimum ellipsoid boundary to the viewer, and *d"* is the distance along the location-to-viewer vector from the transformed minimum ellipsoid boundary to the transformed maximum ellipsoid boundary)
48 1 Nils Peters
49 36 Nils Peters
!X3D.gif!
50 1 Nils Peters
51 36 Nils Peters
 
52 38 Nils Peters
<pre>
53 52 Nils Peters
Sound : X3DSoundNode {
54 52 Nils Peters
  SFVec3f [in,out] direction  0 0 1 (-∞,∞)
55 52 Nils Peters
  SFFloat [in,out] intensity  1     [0,1]
56 52 Nils Peters
  SFVec3f [in,out] location   0 0 0 (-∞,∞)
57 52 Nils Peters
  SFFloat [in,out] maxBack    10    [0,∞)
58 52 Nils Peters
  SFFloat [in,out] maxFront   10    [0,∞)
59 52 Nils Peters
  SFNode  [in,out] metadata   NULL  [X3DMetadataObject]
60 52 Nils Peters
  SFFloat [in,out] minBack    1     [0,∞)
61 52 Nils Peters
  SFFloat [in,out] minFront   1     [0,∞)
62 52 Nils Peters
  SFFloat [in,out] priority   0     [0,1]
63 52 Nils Peters
  SFNode  [in,out] source     NULL  [X3DSoundSourceNode]
64 52 Nils Peters
  SFBool  []       spatialize TRUE
65 52 Nils Peters
}</pre>
66 36 Nils Peters
67 36 Nils Peters
68 36 Nils Peters
69 36 Nils Peters
h2. "DirectX Audio / XACT":http://msdn.microsoft.com/en-us/library/bb147394(VS.85).aspx AUDIO_CONE
70 36 Nils Peters
71 36 Nils Peters
* concentric cones
72 36 Nils Peters
73 36 Nils Peters
* at any angle outside the outer cone, the volume is attenuated. The outside cone volume level is expressed as a linear amplitude scaler: 1.0f represents no attenuation applied to the original signal, 0.5f denotes an attenuation of 6dB, and 0.0f results in silence. Amplification (volume > 1.0f) is also allowed and is not clamped. The valid volume range is actually 0.0f to 2.0f.
74 36 Nils Peters
75 36 Nils Peters
* Between the inner and outer cones is a zone of transition from the inside volume to the outside volume. The volume approaches the cone's outer volume as the angle increases.
76 36 Nils Peters
77 36 Nils Peters
* Cones can affect parameters other than volume. Low pass filter and reverb send level may also be affected. For example, with a cone on the listener, one can specify all sounds behind the listener get a bit muffled and have slightly higher reverb-to-direct ratio content.
78 36 Nils Peters
79 36 Nils Peters
!DirectX-Audio.gif!
80 36 Nils Peters
81 36 Nils Peters
h3. API X3DAUDIO_CONE
82 36 Nils Peters
83 36 Nils Peters
Specifies directionality for a single-channel non-LFE emitter by scaling DSP behavior with respect to the emitter's orientation.
84 36 Nils Peters
85 36 Nils Peters
 
86 36 Nils Peters
<pre>
87 36 Nils Peters
 typedef struct X3DAUDIO_CONE { 
88 36 Nils Peters
     FLOAT32 InnerAngle; 
89 36 Nils Peters
     FLOAT32 OuterAngle; 
90 36 Nils Peters
     FLOAT32 InnerVolume; 
91 36 Nils Peters
     FLOAT32 OuterVolume; 
92 36 Nils Peters
     FLOAT32 InnerLPF; 
93 36 Nils Peters
     FLOAT32 OuterLPF; 
94 36 Nils Peters
     FLOAT32 InnerReverb; 
95 36 Nils Peters
     FLOAT32 OuterReverb; 
96 37 Nils Peters
 } X3DAUDIO_CONE, *LPX3DAUDIO_CONE;
97 36 Nils Peters
</pre>
98 36 Nils Peters
99 36 Nils Peters
Members
100 36 Nils Peters
101 36 Nils Peters
@InnerAngle@: Inner cone angle in radians. This value must be within 0.0f to X3DAUDIO_2PI.
102 36 Nils Peters
@OuterAngle@: Outer cone angle in radians. This value must be within InnerAngle to X3DAUDIO_2PI.
103 36 Nils Peters
@InnerVolume@: Volume scaler on/within inner cone. This value must be within 0.0f to 2.0f.
104 36 Nils Peters
@OuterVolume@: Volume scaler on/beyond outer cone. This value must be within 0.0f to 2.0f.
105 36 Nils Peters
@InnerLPF@: LPF direct-path or reverb-path coefficient scaler on/within inner cone. This value is only used for LPF calculations and must be within 0.0f to 1.0f.
106 36 Nils Peters
@OuterLPF@: LPF direct-path or reverb-path coefficient scaler on or beyond outer cone. This value is only used for LPF calculations and must be within 0.0f to 1.0f.
107 36 Nils Peters
@InnerReverb@: Reverb send level scaler on or within inner cone. This must be within 0.0f to 2.0f.
108 36 Nils Peters
@OuterReverb@: Reverb send level scaler on/beyond outer cone. This must be within 0.0f to 2.0f.
109 36 Nils Peters
110 49 Nils Peters
h2. "CATT":http://www.catt.se/srcdir_mod.htm SD0/SD1/SD2/SD3 format
111 1 Nils Peters
112 48 Nils Peters
    * SD1 based on interpolation from measured 10º full space data: 
113 48 Nils Peters
    * A reference direction is described as "front" and the spatial changes of the relative sound pressure level are specified along semicircle slices  
114 48 Nils Peters
    * The data of each of these slices begin at the reference direction (0°) and are stated in 10° steps on an angle sector of 180°. 
115 48 Nils Peters
    * This results in 19 level readings in dB noting that the first has to be 0 dB as reference point. 
116 48 Nils Peters
    * 36 semicircle slices are to specify for spatial presentation. They all have to cut not only at the reference point "front", but also at the opposite point "back" showing the same level readings. 
117 48 Nils Peters
    * The count direction of the 36 semicircle slices begins vertically above the sound source ("Top") and  looking in reference direction continues counterclockwise by 10° steps (mathematically positive). [adapted from "here":http://www.ptb.de/en/org/1/17/173/richtchar.htm]
118 1 Nils Peters
119 45 Nils Peters
!SD1.gif!
120 1 Nils Peters
121 48 Nils Peters
* legacy format: 
122 48 Nils Peters
       o SD0: based on interpolation from 15º horizontal and vertical polar diagrams
123 48 Nils Peters
* successor formats: 
124 48 Nils Peters
       o SD2: supports loudspeaker array modeling and handles extended near-fields ["more":http://www.catt.se/download_area.htm#DDI_Info] 
125 48 Nils Peters
       o SD3: 5º full space data optionally with phase
126 42 Nils Peters
127 44 Nils Peters
h2. "Common Loudspeaker File Format":http://www.clfgroup.org/  (CLF)
128 42 Nils Peters
129 48 Nils Peters
    * Open file format to describe loudspeaker performance and polar data
130 48 Nils Peters
    * CLF is defined in two parts, a text-based format used for data input and editing, and a binary format for data distribution. 
131 48 Nils Peters
    * "Tools":http://www.clfgroup.org/author.htm are available for data editing, conversion from text to binary format and viewing binary data.
132 48 Nils Peters
    * CLF 1.0 supports two data resolutions. A CLF Type 1 file contains Octave/10 degree data, a CLF Type 2 file contains Third Octave/5 degree data. 
133 42 Nils Peters
134 36 Nils Peters
h1. Files