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csswg/css3-speech Overview.html,1.67,1.68 Overview.src.html,1.68,1.69

From: Daniel Weck via cvs-syncmail <cvsmail@w3.org>
Date: Wed, 13 Jul 2011 15:59:49 +0000
To: public-css-commits@w3.org
Message-Id: <E1Qh1qn-0006aJ-KP@lionel-hutz.w3.org>
Update of /sources/public/csswg/css3-speech
In directory hutz:/tmp/cvs-serv25036

Modified Files:
	Overview.html Overview.src.html 
Log Message:

final paste of my notes for voice-balance.
ready for review.



Index: Overview.html
===================================================================
RCS file: /sources/public/csswg/css3-speech/Overview.html,v
retrieving revision 1.67
retrieving revision 1.68
diff -u -d -r1.67 -r1.68
--- Overview.html	13 Jul 2011 15:15:42 -0000	1.67
+++ Overview.html	13 Jul 2011 15:59:47 -0000	1.68
@@ -706,43 +706,6 @@
    match in the SSML markup language <a href="#SSML"
    rel=biblioentry>[SSML]<!--{{!SSML}}--></a>.
 
-  <ul>
-   <li> When user-agents produce audio via a mono-aural sound system (i.e.
-    single-speaker setup), the &lsquo;<a href="#voice-balance"><code
-    class=property>voice-balance</code></a>&rsquo; property has no effect.
-
-   <li> When user-agents produce audio through a stereo sound system (e.g.
-    two speakers, a pair of headphones), the left-right distribution of audio
-    signals precisely match the authored values for the &lsquo;<a
-    href="#voice-balance"><code
-    class=property>voice-balance</code></a>&rsquo; property.
-
-   <li> When user-agents are capable of mixing audio signals through more
-    than 2 channels (e.g. 5-speakers surround sound system, including a
-    dedicated center channel), the physical distribution of audio signals
-    resulting from the application of the &lsquo;<a
-    href="#voice-balance"><code
-    class=property>voice-balance</code></a>&rsquo; property must be performed
-    so that the listener perceives sound as if it was coming from a basic
-    stereo layout. For example, the center channel as well as the left/right
-    speakers may be used altogether in order to emulate the behavior of the
-    &lsquo;<code class=property>center</code>&rsquo; value (zero, on the
-    [-100,100] scale of the &lsquo;<a href="#voice-balance"><code
-    class=property>voice-balance</code></a>&rsquo; property).
-  </ul>
-
-  <p class=note> Note that sound systems may be configured by users in such a
-   way that it would interfere with the left-right audio distribution
-   specified by document authors. Typically, the various "surround" modes
-   available in modern sound systems (including systems based on basic stereo
-   speakers) tend to greatly alter the perceived spatial arrangement of audio
-   signals. Some users may even configure their system to "downgrade" any
-   rendered sound to a single mono channel, in which case the effect of the
-   &lsquo;<a href="#voice-balance"><code
-   class=property>voice-balance</code></a>&rsquo; property would obviously
-   not be perceivable at all. The rendering fidelity of authored content is
-   therefore dependent on such user customizations.
-
   <dl>
    <dt> <strong>&lt;number&gt;</strong>
 
@@ -793,6 +756,49 @@
      the resulting number to &lsquo;<code class=css>100</code>&rsquo;.</p>
   </dl>
 
+  <p> User agents may be connected to different kinds of sound systems,
+   featuring varying audio mixing capabilities. The expected behavior for
+   mono, stereo, and surround sound systems is defined as follows:
+
+  <ul>
+   <li> When user-agents produce audio via a mono-aural sound system (i.e.
+    single-speaker setup), the &lsquo;<a href="#voice-balance"><code
+    class=property>voice-balance</code></a>&rsquo; property has no effect.
+
+   <li> When user-agents produce audio through a stereo sound system (e.g.
+    two speakers, a pair of headphones), the left-right distribution of audio
+    signals can precisely match the authored values for the &lsquo;<a
+    href="#voice-balance"><code
+    class=property>voice-balance</code></a>&rsquo; property.
+
+   <li> When user-agents are capable of mixing audio signals through more
+    than 2 channels (e.g. 5-speakers surround sound system, including a
+    dedicated center channel), the physical distribution of audio signals
+    resulting from the application of the &lsquo;<a
+    href="#voice-balance"><code
+    class=property>voice-balance</code></a>&rsquo; property should be
+    performed so that the listener perceives sound as if it was coming from a
+    basic stereo layout. For example, the center channel as well as the
+    left/right speakers may be used altogether in order to emulate the
+    behavior of the &lsquo;<code class=property>center</code>&rsquo; value.
+  </ul>
+
+  <p class=note> Note that sound systems may be configured by users in such a
+   way that it would interfere with the left-right audio distribution
+   specified by document authors. Typically, the various "surround" modes
+   available in modern sound systems (including systems based on basic stereo
+   speakers) tend to greatly alter the perceived spatial arrangement of audio
+   signals. The illusion of a three-dimensional sound stage is often achieved
+   using a combination of phase shifting, digital delay, volume control
+   (channel mixing), and other techniques. Some users may even configure
+   their system to "downgrade" any rendered sound to a single mono channel,
+   in which case the effect of the &lsquo;<a href="#voice-balance"><code
+   class=property>voice-balance</code></a>&rsquo; property would obviously
+   not be perceivable at all. The rendering fidelity of authored content is
+   therefore dependent on such user customizations, and the &lsquo;<a
+   href="#voice-balance"><code class=property>voice-balance</code></a>&rsquo;
+   property merely specifies the desired end-result.
+
   <p class=note> Note that many speech synthesizers only generate mono sound,
    and therefore do not intrinsically support the &lsquo;<a
    href="#voice-balance"><code class=property>voice-balance</code></a>&rsquo;
@@ -800,6 +806,40 @@
    occurs at post-synthesis stage (when the speech-enabled user-agent mixes
    the various audio sources authored within the document)
 
+  <p> Future revisions of the CSS Speech module may include support for
+   three-dimensional audio, which would effectively enable authors to specify
+   "azimuth" and "elevation" values. In the future, content authored using
+   the current specification may therefore be consumed by user-agents which
+   are compliant with the version of CSS Speech that supports
+   three-dimensional audio. In order to prepare for this possibility, the
+   values enabled by the current &lsquo;<a href="#voice-balance"><code
+   class=property>voice-balance</code></a>&rsquo; property are designed to
+   remain compatible with "azimuth" angles. More precisely, the mapping
+   between the current left-right audio axis (lateral sound stage) and the
+   envisioned 360 degrees plane around the listener's position is defined as
+   follows:
+
+  <ul>
+   <li>The value &lsquo;<code class=css>0</code>&rsquo; maps to zero degrees
+    (&lsquo;<code class=property>center</code>&rsquo;). This is in "front" of
+    the listener, not from "behind".
+
+   <li>The value &lsquo;<code class=css>-100</code>&rsquo; maps to -40
+    degrees (&lsquo;<code class=property>left</code>&rsquo;). Negative angles
+    are in the counter-clockwise direction (the audio stage is seen from the
+    top).
+
+   <li>The value &lsquo;<code class=css>100</code>&rsquo; maps to 40 degrees
+    (&lsquo;<code class=property>right</code>&rsquo;). Positive angles are in
+    the clockwise direction (the audio stage is seen from the top).
+
+   <li>Intermediary values on the scale from &lsquo;<code
+    class=css>-100</code>&rsquo; to &lsquo;<code class=css>100</code>&rsquo;
+    map to the angles between -40 and 40 degrees in a numerically
+    linearly-proportional manner. For example, &lsquo;<code
+    class=css>-50</code>&rsquo; maps to -20 degrees.
+  </ul>
+
   <h2 id=speaking-props><span class=secno>6. </span>Speaking properties</h2>
 
   <h3 id=speaking-props-speak><span class=secno>6.1. </span>The &lsquo;<a

Index: Overview.src.html
===================================================================
RCS file: /sources/public/csswg/css3-speech/Overview.src.html,v
retrieving revision 1.68
retrieving revision 1.69
diff -u -d -r1.68 -r1.69
--- Overview.src.html	13 Jul 2011 15:15:42 -0000	1.68
+++ Overview.src.html	13 Jul 2011 15:59:47 -0000	1.69
@@ -416,33 +416,9 @@
       lateral sound stage: one extremity is on the left, the other extremity is on the right hand
       side, relative to the listener's position. Authors can specify intermediary steps between left
       and right extremities, to represent the audio separation along the resulting left-right axis. </p>
-
     <p class="note"> Note that the functionality provided by this property has no match in the SSML
       markup language [[!SSML]]. </p>
 
-    <ul>
-      <li> When user-agents produce audio via a mono-aural sound system (i.e. single-speaker setup),
-        the 'voice-balance' property has no effect. </li>
-      <li> When user-agents produce audio through a stereo sound system (e.g. two speakers, a pair
-        of headphones), the left-right distribution of audio signals precisely match the authored
-        values for the 'voice-balance' property. </li>
-      <li> When user-agents are capable of mixing audio signals through more than 2 channels (e.g.
-        5-speakers surround sound system, including a dedicated center channel), the physical
-        distribution of audio signals resulting from the application of the 'voice-balance' property
-        must be performed so that the listener perceives sound as if it was coming from a basic
-        stereo layout. For example, the center channel as well as the left/right speakers may be
-        used altogether in order to emulate the behavior of the 'center' value (zero, on the
-        [-100,100] scale of the 'voice-balance' property). </li>
-    </ul>
-
-    <p class="note"> Note that sound systems may be configured by users in such a way that it would
-      interfere with the left-right audio distribution specified by document authors. Typically, the
-      various "surround" modes available in modern sound systems (including systems based on basic
-      stereo speakers) tend to greatly alter the perceived spatial arrangement of audio signals.
-      Some users may even configure their system to "downgrade" any rendered sound to a single mono
-      channel, in which case the effect of the 'voice-balance' property would obviously not be
-      perceivable at all. The rendering fidelity of authored content is therefore dependent on such
-      user customizations. </p>
     <dl>
       <dt>
         <strong>&lt;number&gt;</strong>
@@ -488,10 +464,60 @@
           clamping the resulting number to '100'.</p>
       </dd>
     </dl>
+
+    <p> User agents may be connected to different kinds of sound systems, featuring varying audio
+      mixing capabilities. The expected behavior for mono, stereo, and surround sound systems is
+      defined as follows: </p>
+    <ul>
+      <li> When user-agents produce audio via a mono-aural sound system (i.e. single-speaker setup),
+        the 'voice-balance' property has no effect. </li>
+      <li> When user-agents produce audio through a stereo sound system (e.g. two speakers, a pair
+        of headphones), the left-right distribution of audio signals can precisely match the
+        authored values for the 'voice-balance' property. </li>
+      <li> When user-agents are capable of mixing audio signals through more than 2 channels (e.g.
+        5-speakers surround sound system, including a dedicated center channel), the physical
+        distribution of audio signals resulting from the application of the 'voice-balance' property
+        should be performed so that the listener perceives sound as if it was coming from a basic
+        stereo layout. For example, the center channel as well as the left/right speakers may be
+        used altogether in order to emulate the behavior of the 'center' value. </li>
+    </ul>
+
+    <p class="note"> Note that sound systems may be configured by users in such a way that it would
+      interfere with the left-right audio distribution specified by document authors. Typically, the
+      various "surround" modes available in modern sound systems (including systems based on basic
+      stereo speakers) tend to greatly alter the perceived spatial arrangement of audio signals. The
+      illusion of a three-dimensional sound stage is often achieved using a combination of phase
+      shifting, digital delay, volume control (channel mixing), and other techniques. Some users may
+      even configure their system to "downgrade" any rendered sound to a single mono channel, in
+      which case the effect of the 'voice-balance' property would obviously not be perceivable at
+      all. The rendering fidelity of authored content is therefore dependent on such user
+      customizations, and the 'voice-balance' property merely specifies the desired end-result. </p>
+
     <p class="note"> Note that many speech synthesizers only generate mono sound, and therefore do
       not intrinsically support the 'voice-balance' property. The sound distribution along the
       left-right axis consequently occurs at post-synthesis stage (when the speech-enabled
       user-agent mixes the various audio sources authored within the document) </p>
+
+    <p> Future revisions of the CSS Speech module may include support for three-dimensional audio,
+      which would effectively enable authors to specify "azimuth" and "elevation" values. In the
+      future, content authored using the current specification may therefore be consumed by
+      user-agents which are compliant with the version of CSS Speech that supports three-dimensional
+      audio. In order to prepare for this possibility, the values enabled by the current
+      'voice-balance' property are designed to remain compatible with "azimuth" angles. More
+      precisely, the mapping between the current left-right audio axis (lateral sound stage) and the
+      envisioned 360 degrees plane around the listener's position is defined as follows: </p>
+    <ul>
+      <li>The value '0' maps to zero degrees ('center'). This is in "front" of the listener, not
+        from "behind".</li>
+      <li>The value '-100' maps to -40 degrees ('left'). Negative angles are in the
+        counter-clockwise direction (the audio stage is seen from the top).</li>
+      <li>The value '100' maps to 40 degrees ('right'). Positive angles are in the clockwise
+        direction (the audio stage is seen from the top).</li>
+      <li>Intermediary values on the scale from '-100' to '100' map to the angles between -40 and 40
+        degrees in a numerically linearly-proportional manner. For example, '-50' maps to -20
+        degrees.</li>
+    </ul>
+
     <h2 id="speaking-props">Speaking properties</h2>
     <h3 id="speaking-props-speak">The 'speak' property</h3>
     <table class="propdef" summary="name: syntax">
Received on Wednesday, 13 July 2011 15:59:55 GMT

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