blob: bed9f875ee24e6d104d334c88275493345d1984e [file] [log] [blame]
* 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.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);
InterFrameDelay::InterFrameDelay() {
// Resets the delay estimate.
void InterFrameDelay::Reset() {
prev_wall_clock_ = absl::nullopt;
prev_rtp_timestamp_unwrapped_ = 0;
// Calculates the delay of a frame with the given timestamp.
// This method is called when the frame is complete.
absl::optional<TimeDelta> InterFrameDelay::CalculateDelay(
uint32_t rtp_timestamp,
Timestamp now) {
int64_t rtp_timestamp_unwrapped = unwrapper_.Unwrap(rtp_timestamp);
if (!prev_wall_clock_) {
// First set of data, initialization, wait for next frame.
prev_wall_clock_ = now;
prev_rtp_timestamp_unwrapped_ = rtp_timestamp_unwrapped;
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_last = static_cast<uint32_t>(prev_rtp_timestamp_unwrapped_);
if (rtp_timestamp_unwrapped < prev_rtp_timestamp_unwrapped_ ||
!IsNewerTimestamp(rtp_timestamp, cropped_last)) {
return absl::nullopt;
// Compute the compensated timestamp difference.
int64_t d_rtp_ticks = rtp_timestamp_unwrapped - prev_rtp_timestamp_unwrapped_;
TimeDelta dts = d_rtp_ticks / k90kHz;
TimeDelta dt = now - *prev_wall_clock_;
// frameDelay is the difference of dT and dTS -- i.e. the difference of the
// wall clock time difference and the timestamp difference between two
// following frames.
TimeDelta delay = dt - dts;
prev_rtp_timestamp_unwrapped_ = rtp_timestamp_unwrapped;
prev_wall_clock_ = now;
return delay;
} // namespace webrtc