Bug 1216460 - [2.2] Refactor SourceBuffer frame eviction and threshold defaults. r=jya

* Move eviction handling out of SourceBuffer into TrackBuffersManager
* Separate audio and video eviction thresholds
* Reduce default audio eviction threshold to 15MB

dom/media/mediasource/SourceBuffer.cpp

@@ -295,8 +295,6 @@ SourceBuffer::SourceBuffer(MediaSource* aMediaSource, const nsACString& aType)
 {
   MOZ_ASSERT(NS_IsMainThread());
   MOZ_ASSERT(aMediaSource);
-  mEvictionThreshold = Preferences::GetUint("media.mediasource.eviction_threshold",
-                                            100 * (1 << 20));
   bool generateTimestamps = false;
   if (aType.LowerCaseEqualsLiteral("audio/mpeg") ||
       aType.LowerCaseEqualsLiteral("audio/aac")) {
@@ -524,11 +522,9 @@ SourceBuffer::PrepareAppend(const uint8_t* aData, uint32_t aLength, ErrorResult&
   TimeUnit newBufferStartTime;
   // Attempt to evict the amount of data we are about to add by lowering the
   // threshold.
-  uint32_t toEvict =
-    (mEvictionThreshold > aLength) ? mEvictionThreshold - aLength : aLength;
   Result evicted =
     mContentManager->EvictData(TimeUnit::FromSeconds(mMediaSource->GetDecoder()->GetCurrentTime()),
-                               toEvict, &newBufferStartTime);
+                               aLength, &newBufferStartTime);
   if (evicted == Result::DATA_EVICTED) {
     MSE_DEBUG("AppendData Evict; current buffered start=%f",
               GetBufferedStart());
@@ -541,7 +537,8 @@ SourceBuffer::PrepareAppend(const uint8_t* aData, uint32_t aLength, ErrorResult&
   // See if we have enough free space to append our new data.
   // As we can only evict once we have playable data, we must give a chance
   // to the DASH player to provide a complete media segment.
-  if (aLength > mEvictionThreshold || evicted == Result::BUFFER_FULL) {
+  if (aLength > mContentManager->EvictionThreshold() ||
+      evicted == Result::BUFFER_FULL) {
     aRv.Throw(NS_ERROR_DOM_QUOTA_EXCEEDED_ERR);
     return nullptr;
   }

dom/media/mediasource/SourceBuffer.h

@@ -253,8 +253,6 @@ private:
 
   RefPtr<MediaSource> mMediaSource;
 
-  uint32_t mEvictionThreshold;
-
   RefPtr<SourceBufferContentManager> mContentManager;
   RefPtr<SourceBufferAttributes> mAttributes;
 

dom/media/mediasource/SourceBufferContentManager.h

@@ -107,6 +107,7 @@ public:
   virtual void SetGroupStartTimestamp(const media::TimeUnit& aGroupStartTimestamp) {}
   virtual void RestartGroupStartTimestamp() {}
   virtual media::TimeUnit GroupEndTimestamp() = 0;
+  virtual int64_t EvictionThreshold() const = 0;
 
 protected:
   virtual ~SourceBufferContentManager() { }

dom/media/mediasource/SourceBufferResource.h

@@ -111,9 +111,9 @@ public:
     ReentrantMonitorAutoEnter mon(mMonitor);
     return mEnded;
   }
-  // Remove data from resource if it holds more than the threshold
-  // number of bytes. Returns amount evicted.
-  uint32_t EvictData(uint64_t aPlaybackOffset, int64_t aThreshold,
+  // Remove data from resource if it holds more than the threshold reduced by
+  // the given number of bytes. Returns amount evicted.
+  uint32_t EvictData(uint64_t aPlaybackOffset, int64_t aThresholdReduct,
                      ErrorResult& aRv);
 
   // Remove data from resource before the given offset.

dom/media/mediasource/TrackBuffersManager.cpp

@@ -99,8 +99,10 @@ TrackBuffersManager::TrackBuffersManager(dom::SourceBufferAttributes* aAttribute
   , mTaskQueue(aParentDecoder->GetDemuxer()->GetTaskQueue())
   , mSourceBufferAttributes(aAttributes)
   , mParentDecoder(new nsMainThreadPtrHolder<MediaSourceDecoder>(aParentDecoder, false /* strict */))
-  , mEvictionThreshold(Preferences::GetUint("media.mediasource.eviction_threshold",
-                                            100 * (1 << 20)))
+  , mVideoEvictionThreshold(Preferences::GetUint("media.mediasource.eviction_threshold.video",
+                                                 100 * 1024 * 1024))
+  , mAudioEvictionThreshold(Preferences::GetUint("media.mediasource.eviction_threshold.audio",
+                                                 15 * 1024 * 1024))
   , mEvictionOccurred(false)
   , mMonitor("TrackBuffersManager")
   , mAppendRunning(false)
@@ -202,9 +204,13 @@ TrackBuffersManager::EvictData(TimeUnit aPlaybackTime,
                                TimeUnit* aBufferStartTime)
 {
   MOZ_ASSERT(NS_IsMainThread());
-  MSE_DEBUG("");
 
-  int64_t toEvict = GetSize() - aThreshold;
+  const int64_t toEvict = GetSize() -
+    std::max(EvictionThreshold() - aThresholdReduct, aThresholdReduct);
+
+  MSE_DEBUG("buffered=%lldkb, eviction threshold=%ukb, evict=%lldkb",
+            GetSize() / 1024, EvictionThreshold() / 1024, toEvict / 1024);
+
   if (toEvict <= 0) {
     return EvictDataResult::NO_DATA_EVICTED;
   }
@@ -351,6 +357,15 @@ TrackBuffersManager::CompleteResetParserState()
   mAppendPromise.RejectIfExists(NS_ERROR_ABORT, __func__);
 }
 
+int64_t
+TrackBuffersManager::EvictionThreshold() const
+{
+  if (HasVideo()) {
+    return mVideoEvictionThreshold;
+  }
+  return mAudioEvictionThreshold;
+}
+
 void
 TrackBuffersManager::DoEvictData(const TimeUnit& aPlaybackTime,
                                  int64_t aSizeToEvict)
@@ -501,7 +516,7 @@ TrackBuffersManager::CodedFrameRemoval(TimeInterval aInterval)
   mSizeSourceBuffer = mVideoTracks.mSizeBuffer + mAudioTracks.mSizeBuffer;
 
   // 4. If buffer full flag equals true and this object is ready to accept more bytes, then set the buffer full flag to false.
-  if (mBufferFull && mSizeSourceBuffer < mEvictionThreshold) {
+  if (mBufferFull && mSizeSourceBuffer < EvictionThreshold()) {
     mBufferFull = false;
   }
   mEvictionOccurred = true;
@@ -1237,7 +1252,7 @@ TrackBuffersManager::CompleteCodedFrameProcessing()
 
   // Return to step 6.4 of Segment Parser Loop algorithm
   // 4. If this SourceBuffer is full and cannot accept more media data, then set the buffer full flag to true.
-  if (mSizeSourceBuffer >= mEvictionThreshold) {
+  if (mSizeSourceBuffer >= EvictionThreshold()) {
     mBufferFull = true;
     mEvictionOccurred = false;
   }

dom/media/mediasource/TrackBuffersManager.h

@@ -77,6 +77,7 @@ public:
   void SetGroupStartTimestamp(const media::TimeUnit& aGroupStartTimestamp) override;
   void RestartGroupStartTimestamp() override;
   media::TimeUnit GroupEndTimestamp() override;
+  int64_t EvictionThreshold() const override;
 
   // Interface for MediaSourceDemuxer
   MediaInfo GetMetadata();
@@ -344,7 +345,8 @@ private:
 
   // Global size of this source buffer content.
   Atomic<int64_t> mSizeSourceBuffer;
-  uint32_t mEvictionThreshold;
+  int64_t mVideoEvictionThreshold;
+  int64_t mAudioEvictionThreshold;
   Atomic<bool> mEvictionOccurred;
 
   // Monitor to protect following objects accessed across multipple threads.