blob: ca52ed9e69e36416fd3c4d3ab3291e67468f4afb [file] [log] [blame]
/*
* Copyright 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.
*/
#include "common_video/include/bitrate_adjuster.h"
#include <algorithm>
#include <cmath>
#include "rtc_base/logging.h"
#include "rtc_base/time_utils.h"
namespace webrtc {
// Update bitrate at most once every second.
const uint32_t BitrateAdjuster::kBitrateUpdateIntervalMs = 1000;
// Update bitrate at most once every 30 frames.
const uint32_t BitrateAdjuster::kBitrateUpdateFrameInterval = 30;
// 10 percent of original.
const float BitrateAdjuster::kBitrateTolerancePct = .1f;
const float BitrateAdjuster::kBytesPerMsToBitsPerSecond = 8 * 1000;
BitrateAdjuster::BitrateAdjuster(float min_adjusted_bitrate_pct,
float max_adjusted_bitrate_pct)
: min_adjusted_bitrate_pct_(min_adjusted_bitrate_pct),
max_adjusted_bitrate_pct_(max_adjusted_bitrate_pct),
bitrate_tracker_(1.5 * kBitrateUpdateIntervalMs,
kBytesPerMsToBitsPerSecond) {
Reset();
}
void BitrateAdjuster::SetTargetBitrateBps(uint32_t bitrate_bps) {
rtc::CritScope cs(&crit_);
// If the change in target bitrate is large, update the adjusted bitrate
// immediately since it's likely we have gained or lost a sizeable amount of
// bandwidth and we'll want to respond quickly.
// If the change in target bitrate fits within the existing tolerance of
// encoder output, wait for the next adjustment time to preserve
// existing penalties and not forcibly reset the adjusted bitrate to target.
// However, if we received many small deltas within an update time
// window and one of them exceeds the tolerance when compared to the last
// target we updated against, treat it as a large change in target bitrate.
if (!IsWithinTolerance(bitrate_bps, target_bitrate_bps_) ||
!IsWithinTolerance(bitrate_bps, last_adjusted_target_bitrate_bps_)) {
adjusted_bitrate_bps_ = bitrate_bps;
last_adjusted_target_bitrate_bps_ = bitrate_bps;
}
target_bitrate_bps_ = bitrate_bps;
}
uint32_t BitrateAdjuster::GetTargetBitrateBps() const {
rtc::CritScope cs(&crit_);
return target_bitrate_bps_;
}
uint32_t BitrateAdjuster::GetAdjustedBitrateBps() const {
rtc::CritScope cs(&crit_);
return adjusted_bitrate_bps_;
}
absl::optional<uint32_t> BitrateAdjuster::GetEstimatedBitrateBps() {
rtc::CritScope cs(&crit_);
return bitrate_tracker_.Rate(rtc::TimeMillis());
}
void BitrateAdjuster::Update(size_t frame_size) {
rtc::CritScope cs(&crit_);
uint32_t current_time_ms = rtc::TimeMillis();
bitrate_tracker_.Update(frame_size, current_time_ms);
UpdateBitrate(current_time_ms);
}
bool BitrateAdjuster::IsWithinTolerance(uint32_t bitrate_bps,
uint32_t target_bitrate_bps) {
if (target_bitrate_bps == 0) {
return false;
}
float delta = std::abs(static_cast<float>(bitrate_bps) -
static_cast<float>(target_bitrate_bps));
float delta_pct = delta / target_bitrate_bps;
return delta_pct < kBitrateTolerancePct;
}
uint32_t BitrateAdjuster::GetMinAdjustedBitrateBps() const {
return min_adjusted_bitrate_pct_ * target_bitrate_bps_;
}
uint32_t BitrateAdjuster::GetMaxAdjustedBitrateBps() const {
return max_adjusted_bitrate_pct_ * target_bitrate_bps_;
}
// Only safe to call this after Update calls have stopped
void BitrateAdjuster::Reset() {
rtc::CritScope cs(&crit_);
target_bitrate_bps_ = 0;
adjusted_bitrate_bps_ = 0;
last_adjusted_target_bitrate_bps_ = 0;
last_bitrate_update_time_ms_ = 0;
frames_since_last_update_ = 0;
bitrate_tracker_.Reset();
}
void BitrateAdjuster::UpdateBitrate(uint32_t current_time_ms) {
uint32_t time_since_last_update_ms =
current_time_ms - last_bitrate_update_time_ms_;
// Don't attempt to update bitrate unless enough time and frames have passed.
++frames_since_last_update_;
if (time_since_last_update_ms < kBitrateUpdateIntervalMs ||
frames_since_last_update_ < kBitrateUpdateFrameInterval) {
return;
}
float target_bitrate_bps = target_bitrate_bps_;
float estimated_bitrate_bps =
bitrate_tracker_.Rate(current_time_ms).value_or(target_bitrate_bps);
float error = target_bitrate_bps - estimated_bitrate_bps;
// Adjust if we've overshot by any amount or if we've undershot too much.
if (estimated_bitrate_bps > target_bitrate_bps ||
error > kBitrateTolerancePct * target_bitrate_bps) {
// Adjust the bitrate by a fraction of the error.
float adjustment = .5 * error;
float adjusted_bitrate_bps = target_bitrate_bps + adjustment;
// Clamp the adjustment.
float min_bitrate_bps = GetMinAdjustedBitrateBps();
float max_bitrate_bps = GetMaxAdjustedBitrateBps();
adjusted_bitrate_bps = std::max(adjusted_bitrate_bps, min_bitrate_bps);
adjusted_bitrate_bps = std::min(adjusted_bitrate_bps, max_bitrate_bps);
// Set the adjustment if it's not already set.
float last_adjusted_bitrate_bps = adjusted_bitrate_bps_;
if (adjusted_bitrate_bps != last_adjusted_bitrate_bps) {
RTC_LOG(LS_VERBOSE) << "Adjusting encoder bitrate:"
"\n target_bitrate:"
<< static_cast<uint32_t>(target_bitrate_bps)
<< "\n estimated_bitrate:"
<< static_cast<uint32_t>(estimated_bitrate_bps)
<< "\n last_adjusted_bitrate:"
<< static_cast<uint32_t>(last_adjusted_bitrate_bps)
<< "\n adjusted_bitrate:"
<< static_cast<uint32_t>(adjusted_bitrate_bps);
adjusted_bitrate_bps_ = adjusted_bitrate_bps;
}
}
last_bitrate_update_time_ms_ = current_time_ms;
frames_since_last_update_ = 0;
last_adjusted_target_bitrate_bps_ = target_bitrate_bps_;
}
} // namespace webrtc