k-rate playbackRate and detune reaches final value

third_party/WebKit/Source/modules/webaudio/AudioParamTimeline.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 839 matching lines @@
     // Optimize the case where the last event is in the past.
     ParamEvent* lastEvent = m_events[m_events.size() - 1].get();
     ParamEvent::Type lastEventType = lastEvent->getType();
     double lastEventTime = lastEvent->time();
 
     // If the last event is in the past and the event has ended, then we can
     // just propagate the same value.  Except for SetTarget which lasts
     // "forever".  SetValueCurve also has an explicit SetValue at the end of
     // the curve, so we don't need to worry that SetValueCurve time is a
     // start time, not an end time.
-    if (lastEventTime < currentTime && lastEventType != ParamEvent::SetTarget) {
+    //
+    // Allow at least one render quantum to go by before handling this
+    // to allow k-rate parameters to finish processing the event. See
+    // crbug.com/672857. Due to possible roundoff, arbirtrarily wait
+    // for 1.5 render quanta instead of 1.

[hongchan, 2017/01/12 23:32:16]

What is the possible side effect of waiting 1.5 RQ?

[Raymond Toy, 2017/01/12 23:49:10]

I think the only side-effect would be that we now end up clearing the event list
after 2 RQ after the last event instead of immediately. I think it's useful to
be able to empty the event list so that we can do the fast path if no events are
added again.

+    if (lastEventTime +
+                1.5 * AudioUtilities::kRenderQuantumFrames / sampleRate <
+            currentTime &&
+        lastEventType != ParamEvent::SetTarget) {

[hongchan, 2017/01/12 23:32:15]

Wow. Is this what 'git cl format' offers? Could you please confirm it?

[Raymond Toy, 2017/01/12 23:46:51]

Yep.  This isn't how I had originally indented it. I tried again and put
everything on one line, and git cl format produces this again.

       // The event has finished, so just copy the default value out.
       // Since all events are now also in the past, we can just remove all
       // timeline events too because |defaultValue| has the expected
       // value.
       for (unsigned i = 0; i < numberOfValues; ++i)
         values[i] = defaultValue;
       m_smoothedValue = defaultValue;
       m_events.clear();
       return defaultValue;
     }
@@ skipping 691 matching lines @@
   // propagate the last value to the end of the values buffer.
   for (; writeIndex < numberOfValues; ++writeIndex)
     values[writeIndex] = value;
 
   // This value is used to set the .value attribute of the AudioParam.  it
   // should be the last computed value.
   return values[numberOfValues - 1];
 }
 
 }  // namespace blink