Change TWCC send interval to reduce overhead on low BW situations.

webrtc/modules/remote_bitrate_estimator/remote_estimator_proxy.cc

 /*
  *  Copyright (c) 2015 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/remote_bitrate_estimator/remote_estimator_proxy.h"
 
 #include <limits>
+#include <utility>
 
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/system_wrappers/include/clock.h"
 #include "webrtc/modules/pacing/packet_router.h"
 #include "webrtc/modules/rtp_rtcp/source/rtcp_packet/transport_feedback.h"
 #include "webrtc/modules/rtp_rtcp/include/rtp_rtcp.h"
 
 namespace webrtc {
 
 // TODO(sprang): Tune these!
-const int RemoteEstimatorProxy::kDefaultProcessIntervalMs = 50;
+const int RemoteEstimatorProxy::kHighBitrateProcessIntervalMs = 50;
+const int RemoteEstimatorProxy::kLowBitrateProcessIntervalMs = 200;
+const int RemoteEstimatorProxy::kSwitchToLowBitrateProcessIntervalBps = 50000;
+const int RemoteEstimatorProxy::kSwitchToHighBitrateProcessIntervalBps = 100000;

[stefan-webrtc, 2016/10/17 18:55:21]

I'm starting to lean towards making the interval a linear function of bitrate
instead. Something like this:
interval = std::max(250 - bitrate, 50)

WDYT?

+const int RemoteEstimatorProxy::kMinPacketCountRecievedBitrate = 50;
 const int RemoteEstimatorProxy::kBackWindowMs = 500;
 
 // The maximum allowed value for a timestamp in milliseconds. This is lower
 // than the numerical limit since we often convert to microseconds.
 static constexpr int64_t kMaxTimeMs =
     std::numeric_limits<int64_t>::max() / 1000;
 
-RemoteEstimatorProxy::RemoteEstimatorProxy(Clock* clock,
-                                           PacketRouter* packet_router)
+RemoteEstimatorProxy::RemoteEstimatorProxy(
+    Clock* clock,
+    PacketRouter* packet_router,
+    std::unique_ptr<rtc::RateTracker> recieved_bitrate_tracker)
     : clock_(clock),
       packet_router_(packet_router),
       last_process_time_ms_(-1),
       media_ssrc_(0),
       feedback_sequence_(0),
-      window_start_seq_(-1) {}
+      window_start_seq_(-1),
+      process_interval_ms_(kHighBitrateProcessIntervalMs),
+      received_bitrate_tracker_bps_(std::move(recieved_bitrate_tracker)) {}
 
 RemoteEstimatorProxy::~RemoteEstimatorProxy() {}
 
 void RemoteEstimatorProxy::IncomingPacketFeedbackVector(
     const std::vector<PacketInfo>& packet_feedback_vector) {
   rtc::CritScope cs(&lock_);
   for (PacketInfo info : packet_feedback_vector)
     OnPacketArrival(info.sequence_number, info.arrival_time_ms);
 }
 
 void RemoteEstimatorProxy::IncomingPacket(int64_t arrival_time_ms,
                                           size_t payload_size,
                                           const RTPHeader& header) {
   if (!header.extension.hasTransportSequenceNumber) {
     LOG(LS_WARNING) << "RemoteEstimatorProxy: Incoming packet "
                        "is missing the transport sequence number extension!";
     return;
   }
   rtc::CritScope cs(&lock_);
   media_ssrc_ = header.ssrc;
-
+  received_bitrate_tracker_bps_->AddSamples(payload_size * 8);
   OnPacketArrival(header.extension.transportSequenceNumber, arrival_time_ms);
 }
 
 bool RemoteEstimatorProxy::LatestEstimate(std::vector<unsigned int>* ssrcs,
                                           unsigned int* bitrate_bps) const {
   return false;
 }
 
 int64_t RemoteEstimatorProxy::TimeUntilNextProcess() {
   int64_t now = clock_->TimeInMilliseconds();
   int64_t time_until_next = 0;
+  {
+    rtc::CritScope cs(&lock_);
+    if (received_bitrate_tracker_bps_->TotalSampleCount() >
+        kMinPacketCountRecievedBitrate) {
+      double recieved_bitrate = received_bitrate_tracker_bps_->ComputeRate();
+      if (recieved_bitrate <= kSwitchToLowBitrateProcessIntervalBps)
+        process_interval_ms_ = kLowBitrateProcessIntervalMs;
+      if (recieved_bitrate >= kSwitchToHighBitrateProcessIntervalBps)
+        process_interval_ms_ = kHighBitrateProcessIntervalMs;
+    }
+  }
   if (last_process_time_ms_ != -1 &&
-      now - last_process_time_ms_ < kDefaultProcessIntervalMs) {
-    time_until_next = (last_process_time_ms_ + kDefaultProcessIntervalMs - now);
+      now - last_process_time_ms_ < process_interval_ms_) {
+    time_until_next = (last_process_time_ms_ + process_interval_ms_ - now);
   }
   return time_until_next;
 }
 
 void RemoteEstimatorProxy::Process() {
   last_process_time_ms_ = clock_->TimeInMilliseconds();
 
   bool more_to_build = true;
   while (more_to_build) {
     rtcp::TransportFeedback feedback_packet;
@@ skipping 88 matching lines @@
     // Note: Don't erase items from packet_arrival_times_ after sending, in case
     // they need to be re-sent after a reordering. Removal will be handled
     // by OnPacketArrival once packets are too old.
     window_start_seq_ = it->first + 1;
   }
 
   return true;
 }
 
 }  // namespace webrtc