Introduce ThresholdCurve (avoids code duplication between PLR/RPLR-based FecController)

webrtc/modules/audio_coding/audio_network_adaptor/fec_controller_rplr_based.h

Index: webrtc/modules/audio_coding/audio_network_adaptor/fec_controller_rplr_based.h
diff --git a/webrtc/modules/audio_coding/audio_network_adaptor/fec_controller_rplr_based.h b/webrtc/modules/audio_coding/audio_network_adaptor/fec_controller_rplr_based.h
index e03ccacf28185bb10433bb36c78b28fc98cca0d4..849f43cc0b363fefc873660e19a1e2282e3a2173 100644
--- a/webrtc/modules/audio_coding/audio_network_adaptor/fec_controller_rplr_based.h
+++ b/webrtc/modules/audio_coding/audio_network_adaptor/fec_controller_rplr_based.h
@@ -15,35 +15,13 @@
 
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/modules/audio_coding/audio_network_adaptor/controller.h"
+#include "webrtc/modules/audio_coding/audio_network_adaptor/util/threshold_curve.h"
 
 namespace webrtc {
 
 class FecControllerRplrBased 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.
-      //
-      // recoverable
-      // packet      ^   |
-      //  loss       | A |
-      //             |    \   A: (low_bandwidth_bps,
-      //             |     \      low_bandwidth_recoverable_packet_loss)
-      //             |      \  B: (high_bandwidth_bps,
-      //             |       \     high_bandwidth_recoverable_packet_loss)
-      //             |      B \________
-      //             |---------------> bandwidth
-      Threshold(int low_bandwidth_bps,
-                float low_bandwidth_recoverable_packet_loss,
-                int high_bandwidth_bps,
-                float high_bandwidth_recoverable_packet_loss);
-      int low_bandwidth_bps;
-      float low_bandwidth_recoverable_packet_loss;
-      int high_bandwidth_bps;
-      float high_bandwidth_recoverable_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
@@ -56,11 +34,11 @@ class FecControllerRplrBased final : public Controller {
     //             | OFF  \_________ fec_disabling_threshold
     //             |-----------------> bandwidth
     Config(bool initial_fec_enabled,
-           const Threshold& fec_enabling_threshold,
-           const Threshold& fec_disabling_threshold);
+           const ThresholdCurve& fec_enabling_threshold,
+           const ThresholdCurve& fec_disabling_threshold);
     bool initial_fec_enabled;
-    Threshold fec_enabling_threshold;
-    Threshold fec_disabling_threshold;
+    ThresholdCurve fec_enabling_threshold;
+    ThresholdCurve fec_disabling_threshold;
   };
 
   explicit FecControllerRplrBased(const Config& config);
@@ -72,18 +50,6 @@ class FecControllerRplrBased final : public Controller {
   void MakeDecision(AudioNetworkAdaptor::EncoderRuntimeConfig* config) override;
 
  private:
-  // Characterize Threshold with:
-  // recoverable_packet_loss = slope * bandwidth + offset.
-  struct ThresholdInfo {
-    explicit ThresholdInfo(const Config::Threshold& threshold);
-    float slope;
-    float offset;
-  };
-
-  float GetPacketLossThreshold(int bandwidth_bps,
-                               const Config::Threshold& threshold,
-                               const ThresholdInfo& threshold_info) const;
-
   bool FecEnablingDecision() const;
   bool FecDisablingDecision() const;
 
@@ -92,9 +58,6 @@ class FecControllerRplrBased final : public Controller {
   rtc::Optional<int> uplink_bandwidth_bps_;
   rtc::Optional<float> uplink_recoverable_packet_loss_;
 
-  const ThresholdInfo fec_enabling_threshold_info_;
-  const ThresholdInfo fec_disabling_threshold_info_;
-
   RTC_DISALLOW_COPY_AND_ASSIGN(FecControllerRplrBased);
 };