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/*
* Copyright (c) 2014 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/remb_suppressor.h"
#include <math.h>
#include "webrtc/system_wrappers/interface/field_trial.h"
namespace webrtc {
// If BWE falls more than this fraction from one REMB to the next,
// classify this as a glitch.
static const double kMaxBweDropRatio = 0.45;
// If we are sending less then this fraction of the last REMB when a glitch
// is detected, start suppressing REMB.
static const double kMinSendBitrateFraction = 0.75;
// Minimum fractional BWE growth per second needed to keep suppressing.
static const double kMinGrowth = 0.015;
RembSuppressor::RembSuppressor(Clock* clock)
: enabled_(false),
clock_(clock),
last_remb_bps_(0),
bitrate_sent_bps_(0),
last_remb_ignored_bps_(0),
last_remb_ignore_time_ms_(0),
remb_silence_start_(0) {
}
RembSuppressor::~RembSuppressor() {
}
bool RembSuppressor::SuppresNewRemb(uint32_t bitrate_bps) {
if (!Enabled())
return false;
if (remb_silence_start_ == 0) {
// Not currently suppressing. Check if there is a bit rate drop
// significant enough to warrant suppression.
return StartSuppressing(bitrate_bps);
}
// Check if signs point to recovery, otherwise back off suppression.
if (!ContinueSuppressing(bitrate_bps)) {
remb_silence_start_ = 0;
last_remb_ignored_bps_ = 0;
last_remb_ignore_time_ms_ = 0;
return false;
}
return true;
}
bool RembSuppressor::StartSuppressing(uint32_t bitrate_bps) {
if (bitrate_bps <
static_cast<uint32_t>(last_remb_bps_ * kMaxBweDropRatio + 0.5)) {
if (bitrate_sent_bps_ <
static_cast<uint32_t>(last_remb_bps_ * kMinSendBitrateFraction + 0.5)) {
int64_t now = clock_->TimeInMilliseconds();
remb_silence_start_ = now;
last_remb_ignore_time_ms_ = now;
last_remb_ignored_bps_ = bitrate_bps;
return true;
}
}
last_remb_bps_ = bitrate_bps;
return false;
}
bool RembSuppressor::ContinueSuppressing(uint32_t bitrate_bps) {
int64_t now = clock_->TimeInMilliseconds();
if (bitrate_bps >= last_remb_bps_) {
// We have fully recovered, stop suppressing!
return false;
}
// If exactly the same REMB, we probably don't have a new estimate. Keep on
// suppressing. However, if REMB is going down or just not increasing fast
// enough (kMinGrowth = 0.015 => REMB should increase by at least 1.5% / s)
// it looks like the link capacity has actually deteriorated and we are
// currently over-utilizing; back off.
if (bitrate_bps != last_remb_ignored_bps_) {
double delta_t = (now - last_remb_ignore_time_ms_) / 1000.0;
double min_increase = pow(1.0 + kMinGrowth, delta_t);
if (bitrate_bps < last_remb_ignored_bps_ * min_increase) {
return false;
}
}
last_remb_ignored_bps_ = bitrate_bps;
last_remb_ignore_time_ms_ = now;
return true;
}
void RembSuppressor::SetBitrateSent(uint32_t bitrate_bps) {
bitrate_sent_bps_ = bitrate_bps;
}
bool RembSuppressor::Enabled() {
return enabled_;
}
void RembSuppressor::SetEnabled(bool enabled) {
enabled_ = enabled &&
webrtc::field_trial::FindFullName(
"WebRTC-ConditionalRembSuppression") == "Enabled";
}
} // namespace webrtc
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