Bug 1324545 - Implement AudioContext getOutputTimestamp(). r=baku

Differential Revision: https://phabricator.services.mozilla.com/D37281

--HG--
extra : moz-landing-system : lando

dom/media/webaudio/AudioContext.cpp

@@ -36,6 +36,7 @@
 #include "mozilla/dom/OscillatorNodeBinding.h"
 #include "mozilla/dom/PannerNodeBinding.h"
 #include "mozilla/dom/PeriodicWaveBinding.h"
+#include "mozilla/dom/Performance.h"
 #include "mozilla/dom/Promise.h"
 #include "mozilla/dom/StereoPannerNodeBinding.h"
 #include "mozilla/dom/WaveShaperNodeBinding.h"
@@ -525,6 +526,28 @@ AudioListener* AudioContext::Listener() {
 
 double AudioContext::OutputLatency() { return Graph()->AudioOutputLatency(); }
 
+void AudioContext::GetOutputTimestamp(AudioTimestamp& aTimeStamp) {
+  if (!Destination()) {
+    aTimeStamp.mContextTime.Construct(0.0);
+    aTimeStamp.mPerformanceTime.Construct(0.0);
+    return;
+  }
+
+  // The currentTime currently being output is the currentTime minus the audio
+  // output latency.
+  aTimeStamp.mContextTime.Construct(
+      std::max(0.0, CurrentTime() - OutputLatency()));
+  nsPIDOMWindowInner* parent = GetParentObject();
+  Performance* perf = parent ? parent->GetPerformance() : nullptr;
+  if (perf) {
+    // Convert to milliseconds.
+    aTimeStamp.mPerformanceTime.Construct(
+        std::max(0., perf->Now() - (OutputLatency() * 1000.)));
+  } else {
+    aTimeStamp.mPerformanceTime.Construct(0.0);
+  }
+}
+
 Worklet* AudioContext::GetAudioWorklet(ErrorResult& aRv) {
   if (!mWorklet) {
     mWorklet = AudioWorkletImpl::CreateWorklet(this, aRv);

dom/media/webaudio/AudioContext.h

@@ -9,6 +9,7 @@
 
 #include "AudioParamDescriptorMap.h"
 #include "mozilla/dom/OfflineAudioContextBinding.h"
+#include "mozilla/dom/AudioContextBinding.h"
 #include "MediaBufferDecoder.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/DOMEventTargetHelper.h"
@@ -200,6 +201,8 @@ class AudioContext final : public DOMEventTargetHelper,
 
   double OutputLatency();
 
+  void GetOutputTimestamp(AudioTimestamp& aTimeStamp);
+
   Worklet* GetAudioWorklet(ErrorResult& aRv);
 
   bool IsRunning() const;

dom/webidl/AudioContext.webidl

@@ -14,13 +14,18 @@ dictionary AudioContextOptions {
              float        sampleRate = 0;
 };
 
+dictionary AudioTimestamp {
+  double contextTime;
+  DOMHighResTimeStamp performanceTime;
+};
+
 [Pref="dom.webaudio.enabled",
  Constructor(optional AudioContextOptions contextOptions = {})]
 interface AudioContext : BaseAudioContext {
 
-    // Bug 1324545: AudioTimestamp                  getOutputTimestamp ();
     readonly        attribute double               baseLatency;
     readonly        attribute double               outputLatency;
+    AudioTimestamp                  getOutputTimestamp();
 
     [Throws]
     Promise<void> suspend();

testing/web-platform/meta/webaudio/idlharness.https.window.js.ini

@@ -20,9 +20,6 @@
   [AudioParam interface: calling cancelAndHoldAtTime(double) on new AudioBufferSourceNode(context).playbackRate with too few arguments must throw TypeError]
     expected: FAIL
 
-  [AudioContext interface: context must inherit property "getOutputTimestamp()" with the proper type]
-    expected: FAIL
-
   [AudioListener interface: context.listener must inherit property "forwardX" with the proper type]
     expected: FAIL
 
@@ -44,9 +41,6 @@
   [MediaElementAudioSourceNode interface: new MediaElementAudioSourceNode(context, {mediaElement: new Audio}) must inherit property "mediaElement" with the proper type]
     expected: FAIL
 
-  [AudioContext interface: operation getOutputTimestamp()]
-    expected: FAIL
-
   [Stringification of new AudioProcessingEvent('', {\n        playbackTime: 0, inputBuffer: buffer, outputBuffer: buffer\n      })]
     expected: FAIL
 

testing/web-platform/meta/webaudio/the-audio-api/the-audiocontext-interface/audiocontext-getoutputtimestamp.html.ini

@@ -1,2 +0,0 @@
-[audiocontext-getoutputtimestamp.html]
-  expected: ERROR