diff options
Diffstat (limited to 'cast/standalone_sender/streaming_video_encoder.cc')
-rw-r--r-- | cast/standalone_sender/streaming_video_encoder.cc | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/cast/standalone_sender/streaming_video_encoder.cc b/cast/standalone_sender/streaming_video_encoder.cc new file mode 100644 index 00000000..0e15ab2c --- /dev/null +++ b/cast/standalone_sender/streaming_video_encoder.cc @@ -0,0 +1,57 @@ +// 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 |