Reland of VCMCodecTimer: Change filter from max to 95th percentile

webrtc/modules/video_coding/codec_timer.h

 /*
  *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_MODULES_VIDEO_CODING_CODEC_TIMER_H_
 #define WEBRTC_MODULES_VIDEO_CODING_CODEC_TIMER_H_
 
+#include <queue>
+
 #include "webrtc/modules/include/module_common_types.h"
+#include "webrtc/modules/video_coding/percentile_filter.h"
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
 
-// MAX_HISTORY_SIZE * SHORT_FILTER_MS defines the window size in milliseconds
-#define MAX_HISTORY_SIZE 10
-#define SHORT_FILTER_MS 1000
-
-class VCMShortMaxSample {
- public:
-  VCMShortMaxSample() : shortMax(0), timeMs(-1) {}
-
-  int32_t shortMax;
-  int64_t timeMs;
-};
-
 class VCMCodecTimer {
  public:
   VCMCodecTimer();
 
-  // Updates the max filtered decode time.
-  void MaxFilter(int32_t newDecodeTimeMs, int64_t nowMs);
+  // Add a new decode time to the filter.
+  void AddTiming(int64_t new_decode_time_ms, int64_t now_ms);
 
-  // Empty the list of timers.
-  void Reset();
-
-  // Get the required decode time in ms.
-  int32_t RequiredDecodeTimeMs(FrameType frameType) const;
+  // Get the required decode time in ms. It is the 95th percentile observed
+  // decode time within a time window.
+  int64_t RequiredDecodeTimeMs() const;
 
  private:
-  void UpdateMaxHistory(int32_t decodeTime, int64_t now);
-  void ProcessHistory(int64_t nowMs);
+  struct Sample {
+    Sample(int64_t decode_time_ms, int64_t sample_time_ms);
+    int64_t decode_time_ms;
+    int64_t sample_time_ms;
+  };
 
-  int32_t _filteredMax;
   // The number of samples ignored so far.
-  int32_t _ignoredSampleCount;
-  int32_t _shortMax;
-  VCMShortMaxSample _history[MAX_HISTORY_SIZE];
+  int ignored_sample_count_;
+  // Queue with history of latest decode time values.
+  std::queue<Sample> history_;
+  // |filter_| contains the same values as |history_|, but in a data structure
+  // that allows efficient retrieval of the percentile value.
+  PercentileFilter filter_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_VIDEO_CODING_CODEC_TIMER_H_