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/*
* Copyright 2021 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/framerate_controller.h"
#include <limits>
#include "rtc_base/time_utils.h"
namespace webrtc {
namespace {
constexpr double kMinFramerate = 0.5;
} // namespace
FramerateController::FramerateController()
: FramerateController(std::numeric_limits<double>::max()) {}
FramerateController::FramerateController(double max_framerate)
: max_framerate_(max_framerate) {}
FramerateController::~FramerateController() {}
void FramerateController::SetMaxFramerate(double max_framerate) {
max_framerate_ = max_framerate;
}
double FramerateController::GetMaxFramerate() const {
return max_framerate_;
}
bool FramerateController::ShouldDropFrame(int64_t in_timestamp_ns) {
if (max_framerate_ < kMinFramerate)
return true;
// If `max_framerate_` is not set (i.e. maxdouble), `frame_interval_ns` is
// rounded to 0.
int64_t frame_interval_ns = rtc::kNumNanosecsPerSec / max_framerate_;
if (frame_interval_ns <= 0) {
// Frame rate throttling not enabled.
return false;
}
if (next_frame_timestamp_ns_) {
// Time until next frame should be outputted.
const int64_t time_until_next_frame_ns =
(*next_frame_timestamp_ns_ - in_timestamp_ns);
// Continue if timestamp is within expected range.
if (std::abs(time_until_next_frame_ns) < 2 * frame_interval_ns) {
// Drop if a frame shouldn't be outputted yet.
if (time_until_next_frame_ns > 0)
return true;
// Time to output new frame.
*next_frame_timestamp_ns_ += frame_interval_ns;
return false;
}
}
// First timestamp received or timestamp is way outside expected range, so
// reset. Set first timestamp target to just half the interval to prefer
// keeping frames in case of jitter.
next_frame_timestamp_ns_ = in_timestamp_ns + frame_interval_ns / 2;
return false;
}
void FramerateController::Reset() {
max_framerate_ = std::numeric_limits<double>::max();
next_frame_timestamp_ns_ = absl::nullopt;
}
void FramerateController::KeepFrame(int64_t in_timestamp_ns) {
if (ShouldDropFrame(in_timestamp_ns)) {
if (max_framerate_ < kMinFramerate)
return;
int64_t frame_interval_ns = rtc::kNumNanosecsPerSec / max_framerate_;
if (next_frame_timestamp_ns_)
*next_frame_timestamp_ns_ += frame_interval_ns;
}
}
} // namespace webrtc
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