Removing the TFRC Rate Control

webrtc/modules/bitrate_controller/send_side_bandwidth_estimation.cc

 /*
  *  Copyright (c) 2012 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.
  */
 
 #include "webrtc/modules/bitrate_controller/send_side_bandwidth_estimation.h"
 
 #include <cmath>
 
 #include "webrtc/base/checks.h"
 #include "webrtc/system_wrappers/interface/field_trial.h"
 #include "webrtc/system_wrappers/interface/logging.h"
 #include "webrtc/system_wrappers/interface/metrics.h"
 
 namespace webrtc {
 namespace {
 const int64_t kBweIncreaseIntervalMs = 1000;
 const int64_t kBweDecreaseIntervalMs = 300;
 const int64_t kStartPhaseMs = 2000;
 const int64_t kBweConverganceTimeMs = 20000;
 const int kLimitNumPackets = 20;
-const int kAvgPacketSizeBytes = 1000;
 const int kDefaultMinBitrateBps = 10000;
 const int kDefaultMaxBitrateBps = 1000000000;
 const int64_t kLowBitrateLogPeriodMs = 10000;
 
 struct UmaRampUpMetric {
   const char* metric_name;
   int bitrate_kbps;
 };
 
 const UmaRampUpMetric kUmaRampupMetrics[] = {
     {"WebRTC.BWE.RampUpTimeTo500kbpsInMs", 500},
     {"WebRTC.BWE.RampUpTimeTo1000kbpsInMs", 1000},
     {"WebRTC.BWE.RampUpTimeTo2000kbpsInMs", 2000}};
 const size_t kNumUmaRampupMetrics =
     sizeof(kUmaRampupMetrics) / sizeof(kUmaRampupMetrics[0]);
 
-// Calculate the rate that TCP-Friendly Rate Control (TFRC) would apply.
-// The formula in RFC 3448, Section 3.1, is used.
-uint32_t CalcTfrcBps(int64_t rtt, uint8_t loss) {
-  if (rtt == 0 || loss == 0) {
-    // Input variables out of range.
-    return 0;
-  }
-  double R = static_cast<double>(rtt) / 1000;  // RTT in seconds.
-  int b = 1;  // Number of packets acknowledged by a single TCP acknowledgement:
-              // recommended = 1.
-  double t_RTO = 4.0 * R;  // TCP retransmission timeout value in seconds
-                           // recommended = 4*R.
-  double p = static_cast<double>(loss) / 255;  // Packet loss rate in [0, 1).
-  double s = static_cast<double>(kAvgPacketSizeBytes);
-
-  // Calculate send rate in bytes/second.
-  double X =
-      s / (R * std::sqrt(2 * b * p / 3) +
-           (t_RTO * (3 * std::sqrt(3 * b * p / 8) * p * (1 + 32 * p * p))));
-
-  // Convert to bits/second.
-  return (static_cast<uint32_t>(X * 8));
-}
 }
 
 SendSideBandwidthEstimation::SendSideBandwidthEstimation()
     : accumulate_lost_packets_Q8_(0),
       accumulate_expected_packets_(0),
       bitrate_(0),
       min_bitrate_configured_(kDefaultMinBitrateBps),
       max_bitrate_configured_(kDefaultMaxBitrateBps),
       last_low_bitrate_log_ms_(-1),
       time_last_receiver_block_ms_(0),
@@ skipping 161 matching lines @@
       if ((now_ms - time_last_decrease_ms_) >=
           (kBweDecreaseIntervalMs + last_round_trip_time_ms_)) {
         time_last_decrease_ms_ = now_ms;
 
         // Reduce rate:
         //   newRate = rate * (1 - 0.5*lossRate);
         //   where packetLoss = 256*lossRate;
         bitrate_ = static_cast<uint32_t>(
             (bitrate_ * static_cast<double>(512 - last_fraction_loss_)) /
             512.0);
-
-        // Calculate what rate TFRC would apply in this situation and to not
-        // reduce further than it.
-        bitrate_ = std::max(
-            bitrate_,
-            CalcTfrcBps(last_round_trip_time_ms_, last_fraction_loss_));
       }
     }
   }
   bitrate_ = CapBitrateToThresholds(now_ms, bitrate_);
 }
 
 bool SendSideBandwidthEstimation::IsInStartPhase(int64_t now_ms) const {
   return first_report_time_ms_ == -1 ||
          now_ms - first_report_time_ms_ < kStartPhaseMs;
 }
@@ skipping 32 matching lines @@
       LOG(LS_WARNING) << "Estimated available bandwidth " << bitrate / 1000
                       << " kbps is below configured min bitrate "
                       << min_bitrate_configured_ / 1000 << " kbps.";
       last_low_bitrate_log_ms_ = now_ms;
     }
     bitrate = min_bitrate_configured_;
   }
   return bitrate;
 }
 }  // namespace webrtc