CHANGELOG.txt for AudioSpatialSound example models

* https://www.web3d.org/x3d/content/examples/X3dForAdvancedModeling/AudioSpatialSound/CHANGELOG.txt

Updates 20 April 2021

a. split out duplicated ID audio_emit as audio_emitter1 and audio_emitter2

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0. TODO: need appropriate meta credit for audio files saxophone.mp3 and violin.ogg

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1. Spelling corrections:

a. emmisiveColor as emissiveColor
b. bind="true" not allowed, since set_bind is an input event
c. Three instances of <Appearance DEF='audio_emit'> renamed as 1, 2, 3 
   respectively to match parent
d. Various occurrences, change id='NAV' to DEF='NAV' but avoid duplication
e. PannerNode to SpatialSound
f. BiquadFilterNode to BiquadFilter
g. jump='TRUE' to jump='true'
h. Viewpoint zNear to nearDistance, zFar to farDistance
i. case sensitive: ambientintensity to ambientIntensity,
   diffusecolor to diffuseColor,
   emissivecolor to emissiveColor,
   specularcolor to specularColor
j. Text has no ccw field, lit field or usegeocache field
k. fontstyle to FontStyle
l. refDistance to referenceDistance
m. SpatialSound position to location
n. SpatialSound orientation (4-tuple) to direction (3-tuple)
o. SpatialSound panningModel='HRTF' to enableHRTF='true'
   SpatialSound enabledHRTF='true' corresponds to panningModelType HRTF,
   enabledHRTF='false' corresponds to panningModelType equalpower. See
   W3C Audio API https://www.w3.org/TR/webaudio/#enumdef-panningmodeltype
p. AudioSource to BufferAudioSource
q. Rename BiquadFilter field Q to qualityFactor
r. Removed pitch='1.0' since we are leaving that solely with legacy nodes
   AudioClip and MovieTexture, not adding further audio functionality to
   existing W3C Audio API.

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2. Units: angles in radians

    coneInnerAngle='360' to coneInnerAngle='6.2832'
    coneOuterAngle='360' to coneOuterAngle='6.2832'

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3. Proposed X3D naming change:

   X3D <AudioBufferSource/> corresponds to W3C Audio API "AudioSource"
   X3D <StreamAudioSource/> corresponds to W3C Audio API "MediaStreamAudioSourceNode"

Improved clarity: rename AudioBufferSource as BufferAudioSource so that we have

   X3D <BufferAudioSource/>
   X3D <StreamAudioSource/>

... which seems like a pretty obvious improvement. Funny we didn't notice it before.
Once again the power of "implement and evaluate!"

Changes applied to XML Schema, DTD, X3DUOM, converters etc. since it is easiest
to test this thoroughly.  If not desirable, we can roll back the rename.

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4. Different addresses in a url list should point to the same logical resource,
varying only in format or location.  Thus

    <AudioSource loop='true' url='"sound/violin.mp3" "sound/violin.ogg"'/>

is OK but

    <AudioSource loop='true' url='"sound/saxophone.mp3" "sound/violin.ogg"'/>

should instead be

    <AudioSource loop='true' url='"sound/saxophone.mp3" "sound/saxophone.ogg"'/>

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5. Not sure about this construct, what is the AudioSound node?  Found in
Efi and Thanos please advise:

    <AudioSound playbackRate='1.0'>
      <Transform USE='Audio1'/>
      <SpatialSound coneInnerAngle='360' coneOuterAngle='360' coneOuterGain='0' direction='1 0 0' distanceModel='inverse' enableHRTF='true' location='0 0 0' maxDistance='10000' referenceDistance='1' rolloffFactor='1'/>
      <BufferAudioSource loop='true' url='"sound/violin.mp3" "sound/violin.ogg"'/>
    </AudioSound>
    <AudioSound playbackRate='1.0'>
      <Transform USE='Audio2'/>
      <SpatialSound coneInnerAngle='360' coneOuterAngle='360' coneOuterGain='0' direction='1 0 0' distanceModel='inverse' enableHRTF='true' location='0 0 0' maxDistance='10000' referenceDistance='1' rolloffFactor='1'/>
      <BufferAudioSource loop='true' url='"sound/saxophone.mp3" "sound/saxophone.ogg"'/>
    </AudioSound>

TODO
Based on playbackRate attribute, it looks like a AudioBufferSourceNode signature
or perhaps a Panner node.  However neither of these wouldn contain another 
SpatialSound as an input child, would it? Does your audio graph fragment need
structuring or is it OK?

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6. BufferAudioSource url field needed

Also looking at your BufferAudioSource url field above, it appears as if this is
an omission in our draft.  If I'm following logic in W3C Web Audio API, the list
of dependencies is:

- 1.9. The AudioBufferSourceNode Interface
  https://www.w3.org/TR/webaudio/#AudioBufferSourceNode

- 1.9.2. Attributes
  buffer, of type AudioBuffer, nullable
  Represents the audio asset to be played.

- 1.4. The AudioBuffer Interface
  https://www.w3.org/TR/webaudio/#AudioBuffer

- copyFromChannel(destination, channelNumber, bufferOffset)
  The copyFromChannel() method copies the samples from the specified channel
  of the AudioBuffer to the destination array.

Our interface starts with:

16.4.5 BufferAudioSource
BufferAudioSource : X3DSoundSourceNode {
  MFFloat  [in,out] buffer                []NULL     [−1,1]
  SFString [in,out] description           ""
  etc.

Seems reasonable that we would want to be able to load an audio file into an
audio graph, and as you have shown, that this is the place to do it.  The only
other node in Sound component which has a url field is the legacy AudioClip node.

Suggest we add X3DUrlObject and first-draft prose:

16.4.5 BufferAudioSource
BufferAudioSource : X3DSoundSourceNode, X3DUrlObject {
  MFFloat  [in,out] buffer                []    [−1,1]
  MFString [in,out] url                   []    [URI]
  SFString [in,out] description           ""
  etc.

"If a /url/ field is provided, then /buffer/ and related fields are initialized
with the contents of the loaded file."

and, copied from AudioClip:

"The url field specifies the URL from which the sound is loaded.
Browsers shall support at least the wavefile format in uncompressed PCM format
(see [WAV]). It is recommended that browsers also support the 
MIDI file type 1 sound format (see 2.[MIDI]) and the 
MP3 compressed format (see 2.[I11172-1]). MIDI files are presumed to use the 
General MIDI patch set. 9.2.1 URLs contains details on the url field."

Pretty straightforward.  Author has option to define data /buffer/ directly in
an X3D scene, or else simply load audio file via url (the usual case).

Definitely deserves group discussion.

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7. Not sure about this:  X3D SpatialSound (which maps to W3C PannerNode) having
a velocity field?

Presumably this is a way to compute doppler shift.  Not finding a direct
parameter mapping in W3C Web Audio PannerNode itself:

* W3C Web Audio API, PannerNode Interface https://www.w3.org/TR/webaudio/#pannernode

Having a way to define doppler seems very helpful.  Authors would have to be
careful that the defined value for velocity matched actual velocity, however.
Perhaps best to leave doppler as a browser capability?

Perhaps even better to define expectations in the X3D Architecture specification
since full knowledge of relative motion exists already in scene graph animation.

Existing summary and suggested change:
=================
16.4.18 SpatialSound

SpatialSound represents a processing node which positions, emits and spatializes an audio stream in three-dimensional (3D) space.

This node provides full spatialization of panner capabilities defined by
W3C Web Audio API [W3C-WebAudio] within an X3D scene.

(draft addition)
SpatialSound sources which are moving spatially in the transformation hierarchy
shall apply velocity-induced frequency shifts corresponding to Doppler effect.
=================

Reference:
* Wikipedia, Doppler effect
  https://en.wikipedia.org/wiki/Doppler_effect

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8. Editors' review of Sound component cleanup

Task: remove HTML markup for prior trial definitions and fields so that
draft specification can be cleanly reviewed, better reflecting the team's intent.

a. No need for acousticProxy field. For simple properties of complex geometry
(e.g. floor wall ceiling acoustics) using simple transparent proxy geometry via
Shape/Appearance/AcousticProperties is sufficient.

b. X3DSoundNode doesn't need to include gain field, only derived types. Refactored.

c. PeriodicWave can implement X3DSoundNode (rather than X3DNode) since it has 
same field signature. No change in parent-child content model.

d. Updated the interface hierarchy diagram, 4.4.2.3 Interface hierarchy
Note rearrangement of tree for consistency.

e. TODO Abstract class  X3DTimeDependentNode likely needs to be renamed as
abstract interface X3DTimeDependentObject for consistency, clarity, and
avoiding multiple inheritance in derived programming languages.

f. Removed gain field from Sound node, since the legacy /intensity/ field is
still there.