89 lines
2.7 KiB
C++
89 lines
2.7 KiB
C++
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/*
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* Copyright 2021 The WebRTC Project Authors. All rights reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "common_video/framerate_controller.h"
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#include <limits>
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#include "rtc_base/time_utils.h"
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namespace webrtc {
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namespace {
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constexpr double kMinFramerate = 0.5;
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} // namespace
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FramerateController::FramerateController()
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: FramerateController(std::numeric_limits<double>::max()) {}
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FramerateController::FramerateController(double max_framerate)
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: max_framerate_(max_framerate) {}
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FramerateController::~FramerateController() {}
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void FramerateController::SetMaxFramerate(double max_framerate) {
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max_framerate_ = max_framerate;
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}
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double FramerateController::GetMaxFramerate() const {
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return max_framerate_;
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}
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bool FramerateController::ShouldDropFrame(int64_t in_timestamp_ns) {
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if (max_framerate_ < kMinFramerate)
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return true;
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// If `max_framerate_` is not set (i.e. maxdouble), `frame_interval_ns` is
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// rounded to 0.
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int64_t frame_interval_ns = rtc::kNumNanosecsPerSec / max_framerate_;
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if (frame_interval_ns <= 0) {
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// Frame rate throttling not enabled.
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return false;
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}
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if (next_frame_timestamp_ns_) {
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// Time until next frame should be outputted.
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const int64_t time_until_next_frame_ns =
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(*next_frame_timestamp_ns_ - in_timestamp_ns);
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// Continue if timestamp is within expected range.
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if (std::abs(time_until_next_frame_ns) < 2 * frame_interval_ns) {
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// Drop if a frame shouldn't be outputted yet.
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if (time_until_next_frame_ns > 0)
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return true;
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// Time to output new frame.
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*next_frame_timestamp_ns_ += frame_interval_ns;
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return false;
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}
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}
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// First timestamp received or timestamp is way outside expected range, so
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// reset. Set first timestamp target to just half the interval to prefer
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// keeping frames in case of jitter.
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next_frame_timestamp_ns_ = in_timestamp_ns + frame_interval_ns / 2;
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return false;
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}
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void FramerateController::Reset() {
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max_framerate_ = std::numeric_limits<double>::max();
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next_frame_timestamp_ns_ = absl::nullopt;
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}
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void FramerateController::KeepFrame(int64_t in_timestamp_ns) {
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if (ShouldDropFrame(in_timestamp_ns)) {
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if (max_framerate_ < kMinFramerate)
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return;
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int64_t frame_interval_ns = rtc::kNumNanosecsPerSec / max_framerate_;
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if (next_frame_timestamp_ns_)
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*next_frame_timestamp_ns_ += frame_interval_ns;
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}
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}
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} // namespace webrtc
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