From f8cd6def9a3aea3f097cd273f0d5ae8c4460b437 Mon Sep 17 00:00:00 2001
From: Alastor Wu <alwu@mozilla.com>
Date: Thu, 21 Jan 2016 10:19:19 +0800
Subject: [PATCH] Bug 1238906 - part1 : check whether audio data is audible.
 r=jwwang

--HG--
extra : rebase_source : 46869a13ba565e0af5413cc2bb387e7c7e0c2df8
---
 dom/media/MediaData.cpp                | 17 +++++++++++++++
 dom/media/MediaData.h                  |  4 ++++
 dom/media/MediaDecoderStateMachine.cpp | 29 ++++++++++++++++++++++++++
 dom/media/MediaDecoderStateMachine.h   |  5 +++++
 4 files changed, 55 insertions(+)

diff --git a/dom/media/MediaData.cpp b/dom/media/MediaData.cpp
index d2f9cc06e283..3ccba39e2f7e 100644
--- a/dom/media/MediaData.cpp
+++ b/dom/media/MediaData.cpp
@@ -54,6 +54,23 @@ AudioData::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
   return size;
 }
 
+bool
+AudioData::IsAudible() const
+{
+  if (!mAudioData) {
+    return false;
+  }
+
+  for (uint32_t frame = 0; frame < mFrames; ++frame) {
+    for (uint32_t channel = 0; channel < mChannels; ++channel) {
+      if (mAudioData[frame * mChannels + channel] != 0) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
 /* static */
 already_AddRefed<AudioData>
 AudioData::TransferAndUpdateTimestampAndDuration(AudioData* aOther,
diff --git a/dom/media/MediaData.h b/dom/media/MediaData.h
index 09e9673cc085..9bf8c6793ca3 100644
--- a/dom/media/MediaData.h
+++ b/dom/media/MediaData.h
@@ -149,6 +149,10 @@ public:
   // If mAudioBuffer is null, creates it from mAudioData.
   void EnsureAudioBuffer();
 
+  // To check whether mAudioData has audible signal, it's used to distinguish
+  // the audiable data and silent data.
+  bool IsAudible() const;
+
   const uint32_t mChannels;
   const uint32_t mRate;
   // At least one of mAudioBuffer/mAudioData must be non-null.
diff --git a/dom/media/MediaDecoderStateMachine.cpp b/dom/media/MediaDecoderStateMachine.cpp
index f092df465e30..9ee0f7b67c47 100644
--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -116,6 +116,11 @@ static const int AUDIO_DURATION_USECS = 40000;
 // increase it by more.
 static const int THRESHOLD_FACTOR = 2;
 
+// When the continuous silent data is over this threshold, means the a/v does
+// not produce any sound. This time is decided by UX suggestion, see
+// https://bugzilla.mozilla.org/show_bug.cgi?id=1235612#c18
+static const uint32_t SILENT_DATA_THRESHOLD_USECS = 10000000;
+
 namespace detail {
 
 // If we have less than this much undecoded data available, we'll consider
@@ -236,6 +241,8 @@ MediaDecoderStateMachine::MediaDecoderStateMachine(MediaDecoder* aDecoder,
   mOutputStreamManager(new OutputStreamManager()),
   mResource(aDecoder->GetResource()),
   mAudioOffloading(false),
+  mIsAudioDataAudible(false),
+  mSilentDataDuration(0),
   mBuffered(mTaskQueue, TimeIntervals(),
             "MediaDecoderStateMachine::mBuffered (Mirror)"),
   mEstimatedDuration(mTaskQueue, NullableTimeUnit(),
@@ -709,14 +716,36 @@ MediaDecoderStateMachine::PushFront(MediaData* aSample, MediaData::Type aSampleT
   UpdateNextFrameStatus();
 }
 
+void
+MediaDecoderStateMachine::CheckIsAudible(const MediaData* aSample)
+{
+  MOZ_ASSERT(OnTaskQueue());
+  MOZ_ASSERT(aSample->mType == MediaData::AUDIO_DATA);
+
+  const AudioData* data = aSample->As<AudioData>();
+  bool isAudible = data->IsAudible();
+  if (isAudible && !mIsAudioDataAudible) {
+    mIsAudioDataAudible = true;
+    mSilentDataDuration = 0;
+  } else if (isAudible && mIsAudioDataAudible) {
+    mSilentDataDuration += data->mDuration;
+    if (mSilentDataDuration > SILENT_DATA_THRESHOLD_USECS) {
+      mIsAudioDataAudible = false;
+      mSilentDataDuration = 0;
+    }
+  }
+}
+
 void
 MediaDecoderStateMachine::OnAudioPopped(const RefPtr<MediaData>& aSample)
 {
   MOZ_ASSERT(OnTaskQueue());
+
   mPlaybackOffset = std::max(mPlaybackOffset.Ref(), aSample->mOffset);
   UpdateNextFrameStatus();
   DispatchAudioDecodeTaskIfNeeded();
   MaybeStartBuffering();
+  CheckIsAudible(aSample);
 }
 
 void
diff --git a/dom/media/MediaDecoderStateMachine.h b/dom/media/MediaDecoderStateMachine.h
index 7e85ed281172..95ce63f72526 100644
--- a/dom/media/MediaDecoderStateMachine.h
+++ b/dom/media/MediaDecoderStateMachine.h
@@ -405,6 +405,7 @@ protected:
   void OnAudioPopped(const RefPtr<MediaData>& aSample);
   void OnVideoPopped(const RefPtr<MediaData>& aSample);
 
+  void CheckIsAudible(const MediaData* aSample);
   void VolumeChanged();
   void LogicalPlaybackRateChanged();
   void PreservesPitchChanged();
@@ -1195,6 +1196,10 @@ private:
   // Playback will not start when audio is offloading.
   bool mAudioOffloading;
 
+  // Used to distiguish continuous silent audio data.
+  bool mIsAudioDataAudible;
+  uint32_t mSilentDataDuration;
+
 #ifdef MOZ_EME
   void OnCDMProxyReady(RefPtr<CDMProxy> aProxy);
   void OnCDMProxyNotReady();