AudioContext "interrupted" state

index.bs

@@ -717,7 +717,8 @@ for="BaseAudioContext">[[control thread state]]</dfn> that take values from
 enum AudioContextState {
     "suspended",
     "running",
-    "closed"
+    "closed",
+    "interrupted"
 };
 </pre>
 
@@ -745,6 +746,12 @@ enum AudioContextState {
             <td>
                 This context has been released, and can no longer be used to
                 process audio. All system audio resources have been released.
+        <tr>
+            <td>
+                "<dfn>interrupted</dfn>"
+            <td>
+                This context is currently interrupted and cannot process audio
+                until the [=interruption=] ends.
 </table>
 </div>
 
@@ -1965,26 +1972,39 @@ Methods</h4>
 
             1. If [=this=]'s [=relevant global object=]'s [=associated Document=] is not [=fully active=] then return [=a promise rejected with=] "{{InvalidStateError}}" {{DOMException}}.
 
-            1. Let <var>promise</var> be a new Promise.
+            2. Let <var>promise</var> be a new Promise.
 
-            2. If the {{[[control thread state]]}} on the
+            3. If the {{[[control thread state]]}} on the
                 {{AudioContext}} is <code>closed</code> reject the
                 promise with {{InvalidStateError}}, abort these steps,
                 returning <var>promise</var>.
 
-            3. Set {{[[suspended by user]]}} to <code>false</code>.
+            4. Set {{[[suspended by user]]}} to <code>false</code>.
+
+            5. If the {{[[control thread state]]}} on the
+                {{AudioContext}} is <code>suspended</code> and there is an ongoing [=interruption=]:
 
-            4. If the context is not <a>allowed to start</a>, append
+                1. Queue a media element task</a> to execute the following steps:
+
+                    1. Set the {{BaseAudioContext/state}} attribute of the {{AudioContext}} to "{{AudioContextState/interrupted}}".
+
+                    2. [=Queue a media element task=] to [=fire an event=] named
+                            {{BaseAudioContext/statechange}} at the {{AudioContext}}.
+
+                2. Reject the promise with {{InvalidStateError}}, abort these steps,
+                returning <var>promise</var>.
+
+            6. If the context is not <a>allowed to start</a>, append
                 <var>promise</var> to {{BaseAudioContext/[[pending promises]]}} and
                 {{AudioContext/[[pending resume promises]]}} and abort these steps, returning
                 <var>promise</var>.
 
-            5. Set the {{[[control thread state]]}} on the
+            7. Set the {{[[control thread state]]}} on the
                 {{AudioContext}} to <code>running</code>.
 
-            6. <a>Queue a control message</a> to resume the {{AudioContext}}.
+            8. <a>Queue a control message</a> to resume the {{AudioContext}}.
 
-            7. Return <var>promise</var>.
+            9. Return <var>promise</var>.
         </div>
 
         <div id="context-resume" algorithm="run a control message in AudioContext">
@@ -4196,7 +4216,7 @@ Methods</h4>
         scheduled parameter changes with times greater than or equal to
         {{AudioParam/cancelAndHoldAtTime()/cancelTime!!argument}}. However, in addition, the automation
         value that would have happened at {{AudioParam/cancelAndHoldAtTime()/cancelTime!!argument}} is
-        then proprogated for all future time until other automation
+        then propagated for all future time until other automation
         events are introduced.
 
         The behavior of the timeline in the face of
@@ -11662,7 +11682,7 @@ and a <a>rendering thread</a>.
 
 The <dfn>control thread</dfn> is the thread from which the
 {{AudioContext}} is instantiated, and from which authors
-manipulate the audio graph, that is, from where the operation on a
+manipulate the audio graph, that is, from where the operations on a
 {{BaseAudioContext}} are invoked. The <dfn>rendering thread</dfn>
 is the thread on which the actual audio output is computed, in
 reaction to the calls from the <a>control thread</a>. It can be a
@@ -11769,7 +11789,7 @@ The algorithm for rendering a block of audio from a {{BaseAudioContext}}
 in the algorithm of <a href="#rendering-a-graph">rendering a graph</a>.
 
 The {{AudioContext}} <a>rendering thread</a> is driven by a
-<dfn>system-level audio callback</dfn>, that is periodically 
+<dfn>system-level audio callback</dfn>, that is periodically called
 at regular intevals. Each call has a <dfn>system-level audio callback buffer
 size</dfn>, which is a varying number of sample-frames that needs to be
 computed on time before the next <a>system-level audio callback</a> arrives.
@@ -12089,6 +12109,69 @@ running the algorithm for an {{AudioNode}}, using an <a>input
 buffer</a> and the value(s) of the {{AudioParam}}(s) of this
 {{AudioNode}} as the input for this algorithm.
 
+<h3 id="interruption-handling">Handling an interruption on the {{AudioContext}}</h3>
+
+An <dfn>interruption</dfn> is an event generated by the user agent when it needs to halt audio playback for 
+an {{AudioContext}}. For example, The user agent may create an interruption when another application
+requests exclusive access to the audio output hardware. This could happen when there is an incoming
+call from a VoIP application.
+
+The {{AudioContext}} |audioContext| performs the following steps on the <a>rendering thread</a> when an interruption happens.
+
+1. If the |audioContext|'s {{[[rendering thread state]]}} is <code>closed</code> or <code>interrupted</code>:
+
+    1. Abort these steps.
+
+1. If the |audioContext|'s {{[[rendering thread state]]}} is <code>running</code>:
+
+    1. Attempt to <a>release system resources</a>.
+
+    1. [=Queue a media element task=] to execute the following steps:
+
+        1. Set the |audioContext|'s {{[[control thread state]]}} to <code>interrupted</code>.
+
+        1. [=Fire an event=] named {{BaseAudioContext/statechange}} at the |audioContext|.
+
+1. If the |audioContext|'s {{[[rendering thread state]]}} is <code>suspended</code>:
+
+    1. [=Queue a media element task=] to execute the following steps:
+
+        1. Set the |audioContext|'s {{[[control thread state]]}} to <code>interrupted</code>.
+
+1. Set the |audioContext|'s {{[[rendering thread state]]}} to <code>interrupted</code>. 
+
+Note: If the {{AudioContext}} is <code>suspended</code> a {{BaseAudioContext/statechange}} event is not fired for privacy reasons to avoid over-sharing user activity - e.g. when a phone call comes in or when the screen gets locked.
+
+The {{AudioContext}} |audioContext| performs the following steps on the <a>rendering thread</a> when the [=interruption=] ends.
+
+1. If the |audioContext|'s {{[[rendering thread state]]}} is not <code>interrupted</code>:
+
+    1. Abort these steps.
+
+1. If the |audioContext|'s {{[[rendering thread state]]}} was <code>running</code> before the [=interruption=] or if the the |audioContext|'s {{[[rendering thread state]]}} was <code>suspended</code> and {{AudioContext/resume}} was called during the [=interruption=]:
+
+    1. Attempt to <a href="#acquiring">acquire system resources</a>.
+
+    2. Set the {{[[rendering thread state]]}} on the {{AudioContext}} to <code>running</code>.
+
+    3. Start <a href="#rendering-loop">rendering the audio graph</a>.
+
+    4. [=Queue a media element task=] to execute the following steps:
+
+        1. If the {{BaseAudioContext/state}} attribute of the {{AudioContext}} is not already "{{AudioContextState/running}}":
+
+            1. Set the |audioContext|'s {{[[control thread state]]}} to <code>running</code>.
+
+            1. [=Fire an event=] named {{BaseAudioContext/statechange}} at the |audioContext|.
+
+1. If the |audioContext|'s {{[[rendering thread state]]}} was <code>suspended</code> before the [=interruption=]:
+
+    1. Set the {{[[rendering thread state]]}} on the {{AudioContext}} to <code>suspended</code>.
+
+    2. [=Queue a media element task=] to execute the following steps:
+
+        1. Set the |audioContext|'s {{[[control thread state]]}} to <code>suspended</code>.
+
 <h3 id="error-handling-on-a-running-audio-context">
     Handling an error from System Audio Resources on the {{AudioContext}}</h3>