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/*
* Copyright (c) 2011 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 "modules/video_coding/timing/inter_frame_delay_variation_calculator.h"
#include "absl/types/optional.h"
#include "api/units/frequency.h"
#include "api/units/time_delta.h"
#include "modules/include/module_common_types_public.h"
namespace webrtc {
namespace {
constexpr Frequency k90kHz = Frequency::KiloHertz(90);
}
InterFrameDelayVariationCalculator::InterFrameDelayVariationCalculator() {
Reset();
}
void InterFrameDelayVariationCalculator::Reset() {
prev_wall_clock_ = absl::nullopt;
prev_rtp_timestamp_unwrapped_ = 0;
}
absl::optional<TimeDelta> InterFrameDelayVariationCalculator::Calculate(
uint32_t rtp_timestamp,
Timestamp now) {
int64_t rtp_timestamp_unwrapped = unwrapper_.Unwrap(rtp_timestamp);
if (!prev_wall_clock_) {
prev_wall_clock_ = now;
prev_rtp_timestamp_unwrapped_ = rtp_timestamp_unwrapped;
// Inter-frame delay variation is undefined for a single frame.
// TODO(brandtr): Should this return absl::nullopt instead?
return TimeDelta::Zero();
}
// Account for reordering in jitter variance estimate in the future?
// Note that this also captures incomplete frames which are grabbed for
// decoding after a later frame has been complete, i.e. real packet losses.
uint32_t cropped_prev = static_cast<uint32_t>(prev_rtp_timestamp_unwrapped_);
if (rtp_timestamp_unwrapped < prev_rtp_timestamp_unwrapped_ ||
!IsNewerTimestamp(rtp_timestamp, cropped_prev)) {
return absl::nullopt;
}
// Compute the compensated timestamp difference.
TimeDelta delta_wall = now - *prev_wall_clock_;
int64_t d_rtp_ticks = rtp_timestamp_unwrapped - prev_rtp_timestamp_unwrapped_;
TimeDelta delta_rtp = d_rtp_ticks / k90kHz;
// The inter-frame delay variation is the second order difference between the
// RTP and wall clocks of the two frames, or in other words, the first order
// difference between `delta_rtp` and `delta_wall`.
TimeDelta inter_frame_delay_variation = delta_wall - delta_rtp;
prev_wall_clock_ = now;
prev_rtp_timestamp_unwrapped_ = rtp_timestamp_unwrapped;
return inter_frame_delay_variation;
}
} // namespace webrtc
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