Adding FecController to audio network adaptor.

webrtc/modules/audio_coding/audio_network_adaptor/fec_controller.h

+/*
+ *  Copyright (c) 2016 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_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_FEC_CONTROLLER_H_
+#define WEBRTC_MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_FEC_CONTROLLER_H_
+
+#include <memory>
+
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/modules/audio_coding/audio_network_adaptor/controller.h"
+#include "webrtc/modules/audio_coding/audio_network_adaptor/smoothing_filter.h"
+
+namespace webrtc {
+
+class FecController final : public Controller {
+ public:
+  struct Config {
+    struct Threshold {
+      // Threshold defines a curve in the bandwidth/packet-loss domain. The
+      // curve is characterized by the two conjunction points: A and B.
+      //
+      // packet ^  |
+      //  loss  | A|
+      //        |   \        A: (low_bandwidth_bps, low_bandwidth_packet_loss)
+      //        |    \       B: (high_bandwidth_bps, high_bandwidth_packet_loss)
+      //        |    B\________
+      //        |---------------> bandwidth
+      Threshold(int low_bandwidth_bps,
+                float low_bandwidth_packet_loss,
+                int high_bandwidth_bps,
+                float high_bandwidth_packet_loss);
+      int low_bandwidth_bps;
+      float low_bandwidth_packet_loss;
+      int high_bandwidth_bps;
+      float high_bandwidth_packet_loss;
+    };
+
+    // |fec_enabling_threshold| defines a curve, above which FEC should be
+    // enabled. |fec_disabling_threshold| defines a curve, under which FEC
+    // should be disabled. See below
+    //
+    // packet-loss ^   |  |
+    //             |   |  |   FEC
+    //             |    \  \   ON
+    //             | FEC \  \_______ fec_enabling_threshold
+    //             | OFF  \_________ fec_disabling_threshold
+    //             |-----------------> bandwidth
+    Config(bool initial_fec_enabled,
+           const Threshold& fec_enabling_threshold,
+           const Threshold& fec_disabling_threshold,
+           int time_constant_ms,
+           Clock* clock);
+    bool initial_fec_enabled;
+    Threshold fec_enabling_threshold;
+    Threshold fec_disabling_threshold;
+    int time_constant_ms;
+    Clock* clock;
+  };
+
+  explicit FecController(const Config& config);
+
+  // Dependency injection for testing.
+  FecController(const Config& config,
+                std::unique_ptr<SmoothingFilter> smoothing_filter);
+
+  ~FecController() override;
+
+  void MakeDecision(const NetworkMetrics& metrics,
+                    AudioNetworkAdaptor::EncoderRuntimeConfig* config) override;
+
+ private:
+  // Characterize Threshold with packet_loss = slope * bandwidth + offset.
+  struct ThresholdInfo {
+    explicit ThresholdInfo(const Config::Threshold& threshold);
+    float slope;
+    float offset;
+  };
+
+  float GetPacketLossThreshold(
+      int bandwidth_bps,
+      const FecController::ThresholdInfo& threshold_info) const;
+  bool FecEnablingDecision(const NetworkMetrics& metrics) const;
+  bool FecDisablingDecision(const NetworkMetrics& metrics) const;
+
+  const Config config_;
+  bool fec_enabled_;
+  std::unique_ptr<SmoothingFilter> packet_loss_smoothed_;
+
+  const ThresholdInfo fec_enabling_threshold_info_;
+  const ThresholdInfo fec_disabling_threshold_info_;
+
+  RTC_DISALLOW_COPY_AND_ASSIGN(FecController);
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_FEC_CONTROLLER_H_