diff --git a/dom/media/DecodedStream.cpp b/dom/media/DecodedStream.cpp
index 0430c23c6054..dcc950228f72 100644
--- a/dom/media/DecodedStream.cpp
+++ b/dom/media/DecodedStream.cpp
@@ -628,13 +628,18 @@ DecodedStream::SendData(double aVolume, bool aIsSameOrigin)
   return finished;
 }
 
-CheckedInt64
+int64_t
 DecodedStream::AudioEndTime() const
 {
   ReentrantMonitorAutoEnter mon(GetReentrantMonitor());
-  MOZ_ASSERT(mStartTime.isSome(), "Must be called after StartPlayback()");
-  return mStartTime.ref() +
-         FramesToUsecs(mData->mAudioFramesWritten, mInfo.mAudio.mRate);
+  if (mStartTime.isSome() && mInfo.HasAudio()) {
+    CheckedInt64 t = mStartTime.ref() +
+      FramesToUsecs(mData->mAudioFramesWritten, mInfo.mAudio.mRate);
+    if (t.isValid()) {
+      return t.value();
+    }
+  }
+  return -1;
 }
 
 int64_t
diff --git a/dom/media/DecodedStream.h b/dom/media/DecodedStream.h
index edba87cebc37..8b25b95c9f7d 100644
--- a/dom/media/DecodedStream.h
+++ b/dom/media/DecodedStream.h
@@ -111,7 +111,7 @@ public:
   void Connect(ProcessedMediaStream* aStream, bool aFinishWhenEnded);
   void Remove(MediaStream* aStream);
   void SetPlaying(bool aPlaying);
-  CheckedInt64 AudioEndTime() const;
+  int64_t AudioEndTime() const;
   int64_t GetPosition() const;
   bool IsFinished() const;
 
diff --git a/dom/media/MediaDecoderStateMachine.cpp b/dom/media/MediaDecoderStateMachine.cpp
index d4f2fc432e11..b66849879b22 100644
--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -372,13 +372,6 @@ void MediaDecoderStateMachine::SendStreamData()
 
   bool finished = mDecodedStream->SendData(mVolume, mDecoder->IsSameOriginMedia());
 
-  if (mInfo.HasAudio()) {
-    CheckedInt64 playedUsecs = mDecodedStream->AudioEndTime();
-    if (playedUsecs.isValid()) {
-      OnAudioEndTimeUpdate(playedUsecs.value());
-    }
-  }
-
   const auto clockTime = GetClock();
   while (true) {
     const AudioData* a = AudioQueue().PeekFront();
@@ -3080,11 +3073,14 @@ MediaDecoderStateMachine::AudioEndTime() const
   AssertCurrentThreadInMonitor();
   if (mAudioSink) {
     return mAudioSink->GetEndTime();
+  } else if (mAudioCaptured) {
+    return mDecodedStream->AudioEndTime();
   }
   // Don't call this after mAudioSink becomes null since we can't distinguish
-  // "before StartAudioThread" and "after StopAudioThread".
-  MOZ_ASSERT(mAudioCaptured || !mAudioCompleted);
-  return mAudioEndTime;
+  // "before StartAudioThread" and "after StopAudioThread" where mAudioSink
+  // is null in both cases.
+  MOZ_ASSERT(!mAudioCompleted);
+  return -1;
 }
 
 void MediaDecoderStateMachine::OnAudioEndTimeUpdate(int64_t aAudioEndTime)