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// Copyright 2021 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "cast/standalone_sender/streaming_video_encoder.h"
#include "util/chrono_helpers.h"
namespace openscreen {
namespace cast {
StreamingVideoEncoder::StreamingVideoEncoder(const Parameters& params,
TaskRunner* task_runner,
Sender* sender)
: params_(params), main_task_runner_(task_runner), sender_(sender) {
OSP_DCHECK_LE(1, params_.num_encode_threads);
OSP_DCHECK_LE(kMinQuantizer, params_.min_quantizer);
OSP_DCHECK_LE(params_.min_quantizer, params_.max_cpu_saver_quantizer);
OSP_DCHECK_LE(params_.max_cpu_saver_quantizer, params_.max_quantizer);
OSP_DCHECK_LE(params_.max_quantizer, kMaxQuantizer);
OSP_DCHECK_LT(0.0, params_.max_time_utilization);
OSP_DCHECK_LE(params_.max_time_utilization, 1.0);
OSP_DCHECK(main_task_runner_);
OSP_DCHECK(sender_);
}
StreamingVideoEncoder::~StreamingVideoEncoder() {}
void StreamingVideoEncoder::UpdateSpeedSettingForNextFrame(const Stats& stats) {
OSP_DCHECK_EQ(std::this_thread::get_id(), encode_thread_.get_id());
// Combine the speed setting that was used to encode the last frame, and the
// quantizer the encoder chose into a single speed metric.
const double speed = current_speed_setting_ +
kEquivalentEncodingSpeedStepPerQuantizerStep *
std::max(0, stats.quantizer - params_.min_quantizer);
// Like |Stats::perfect_quantizer|, this computes a "hindsight" speed setting
// for the last frame, one that may have potentially allowed for a
// better-quality quantizer choice by the encoder, while also keeping CPU
// utilization within budget.
const double perfect_speed =
speed * stats.time_utilization() / params_.max_time_utilization;
// Update the ideal speed setting, to be used for the next frame. An
// exponentially-decaying weighted average is used here to smooth-out noise.
// The weight is based on the duration of the frame that was encoded.
constexpr Clock::duration kDecayHalfLife = milliseconds(120);
const double ticks = stats.frame_duration.count();
const double weight = ticks / (ticks + kDecayHalfLife.count());
ideal_speed_setting_ =
weight * perfect_speed + (1.0 - weight) * ideal_speed_setting_;
OSP_DCHECK(std::isfinite(ideal_speed_setting_));
}
} // namespace cast
} // namespace openscreen
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