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/*
* Copyright (c) 2022 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/timestamp_extrapolator.h"
#include <stdint.h>
#include <limits>
#include <optional>
#include "api/units/frequency.h"
#include "api/units/time_delta.h"
#include "api/units/timestamp.h"
#include "system_wrappers/include/clock.h"
#include "test/gmock.h"
#include "test/gtest.h"
namespace webrtc {
using ::testing::Eq;
using ::testing::Optional;
namespace {
constexpr Frequency kRtpHz = Frequency::KiloHertz(90);
constexpr Frequency k25Fps = Frequency::Hertz(25);
constexpr TimeDelta k25FpsDelay = 1 / k25Fps;
} // namespace
TEST(TimestampExtrapolatorTest, ExtrapolationOccursAfter2Packets) {
SimulatedClock clock(Timestamp::Millis(1337));
TimestampExtrapolator ts_extrapolator(clock.CurrentTime());
// No packets so no timestamp.
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(90000), Eq(std::nullopt));
uint32_t rtp = 90000;
clock.AdvanceTime(k25FpsDelay);
// First result is a bit confusing since it is based off the "start" time,
// which is arbitrary.
ts_extrapolator.Update(clock.CurrentTime(), rtp);
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp),
Optional(clock.CurrentTime()));
rtp += kRtpHz / k25Fps;
clock.AdvanceTime(k25FpsDelay);
ts_extrapolator.Update(clock.CurrentTime(), rtp);
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp),
Optional(clock.CurrentTime()));
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp + 90000),
Optional(clock.CurrentTime() + TimeDelta::Seconds(1)));
}
TEST(TimestampExtrapolatorTest, ResetsAfter10SecondPause) {
SimulatedClock clock(Timestamp::Millis(1337));
TimestampExtrapolator ts_extrapolator(clock.CurrentTime());
uint32_t rtp = 90000;
ts_extrapolator.Update(clock.CurrentTime(), rtp);
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp),
Optional(clock.CurrentTime()));
rtp += kRtpHz / k25Fps;
clock.AdvanceTime(k25FpsDelay);
ts_extrapolator.Update(clock.CurrentTime(), rtp);
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp),
Optional(clock.CurrentTime()));
rtp += 10 * kRtpHz.hertz();
clock.AdvanceTime(TimeDelta::Seconds(10) + TimeDelta::Micros(1));
ts_extrapolator.Update(clock.CurrentTime(), rtp);
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp),
Optional(clock.CurrentTime()));
}
TEST(TimestampExtrapolatorTest, TimestampExtrapolatesMultipleRtpWrapArounds) {
SimulatedClock clock(Timestamp::Millis(1337));
TimestampExtrapolator ts_extrapolator(clock.CurrentTime());
uint32_t rtp = std::numeric_limits<uint32_t>::max();
ts_extrapolator.Update(clock.CurrentTime(), rtp);
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp),
Optional(clock.CurrentTime()));
// One overflow. Static cast to avoid undefined behaviour with +=.
rtp += static_cast<uint32_t>(kRtpHz / k25Fps);
clock.AdvanceTime(k25FpsDelay);
ts_extrapolator.Update(clock.CurrentTime(), rtp);
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp),
Optional(clock.CurrentTime()));
// Assert that extrapolation works across the boundary as expected.
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp + 90000),
Optional(clock.CurrentTime() + TimeDelta::Seconds(1)));
// This is not quite 1s since the math always rounds up.
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp - 90000),
Optional(clock.CurrentTime() - TimeDelta::Millis(999)));
// In order to avoid a wrap arounds reset, add a packet every 10s until we
// overflow twice.
constexpr TimeDelta kRtpOverflowDelay =
std::numeric_limits<uint32_t>::max() / kRtpHz;
const Timestamp overflow_time = clock.CurrentTime() + kRtpOverflowDelay * 2;
while (clock.CurrentTime() < overflow_time) {
clock.AdvanceTime(TimeDelta::Seconds(10));
// Static-cast before += to avoid undefined behaviour of overflow.
rtp += static_cast<uint32_t>(kRtpHz * TimeDelta::Seconds(10));
ts_extrapolator.Update(clock.CurrentTime(), rtp);
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp),
Optional(clock.CurrentTime()));
}
}
TEST(TimestampExtrapolatorTest, NegativeRtpTimestampWrapAround) {
SimulatedClock clock(Timestamp::Millis(1337));
TimestampExtrapolator ts_extrapolator(clock.CurrentTime());
uint32_t rtp = 0;
ts_extrapolator.Update(clock.CurrentTime(), rtp);
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp),
Optional(clock.CurrentTime()));
// Go backwards! Static cast to avoid undefined behaviour with -=.
rtp -= static_cast<uint32_t>(kRtpHz.hertz());
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp),
Optional(clock.CurrentTime() - TimeDelta::Seconds(1)));
}
TEST(TimestampExtrapolatorTest, NegativeRtpTimestampWrapAroundSecondScenario) {
SimulatedClock clock(Timestamp::Millis(1337));
TimestampExtrapolator ts_extrapolator(clock.CurrentTime());
uint32_t rtp = 0;
ts_extrapolator.Update(clock.CurrentTime(), rtp);
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp),
Optional(clock.CurrentTime()));
// Go backwards! Static cast to avoid undefined behaviour with -=.
rtp -= static_cast<uint32_t>(kRtpHz * TimeDelta::Seconds(10));
ts_extrapolator.Update(clock.CurrentTime(), rtp);
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp), std::nullopt);
}
TEST(TimestampExtrapolatorTest, Slow90KHzClock) {
// This simulates a slow camera, which produces frames at 24Hz instead of
// 25Hz. The extrapolator should be able to resolve this with enough data.
SimulatedClock clock(Timestamp::Millis(1337));
TimestampExtrapolator ts_extrapolator(clock.CurrentTime());
constexpr TimeDelta k24FpsDelay = 1 / Frequency::Hertz(24);
uint32_t rtp = 90000;
ts_extrapolator.Update(clock.CurrentTime(), rtp);
// Slow camera will increment RTP at 25 FPS rate even though its producing at
// 24 FPS. After 25 frames the extrapolator should settle at this rate.
for (int i = 0; i < 25; ++i) {
rtp += kRtpHz / k25Fps;
clock.AdvanceTime(k24FpsDelay);
ts_extrapolator.Update(clock.CurrentTime(), rtp);
}
// The camera would normally produce 25 frames in 90K ticks, but is slow
// so takes 1s + k24FpsDelay for 90K ticks.
constexpr Frequency kSlowRtpHz = 90000 / (25 * k24FpsDelay);
// The extrapolator will be predicting that time at millisecond precision.
auto ts = ts_extrapolator.ExtrapolateLocalTime(rtp + kSlowRtpHz.hertz());
ASSERT_TRUE(ts.has_value());
EXPECT_EQ(ts->ms(), clock.TimeInMilliseconds() + 1000);
}
TEST(TimestampExtrapolatorTest, Fast90KHzClock) {
// This simulates a fast camera, which produces frames at 26Hz instead of
// 25Hz. The extrapolator should be able to resolve this with enough data.
SimulatedClock clock(Timestamp::Millis(1337));
TimestampExtrapolator ts_extrapolator(clock.CurrentTime());
constexpr TimeDelta k26FpsDelay = 1 / Frequency::Hertz(26);
uint32_t rtp = 90000;
ts_extrapolator.Update(clock.CurrentTime(), rtp);
// Fast camera will increment RTP at 25 FPS rate even though its producing at
// 26 FPS. After 25 frames the extrapolator should settle at this rate.
for (int i = 0; i < 25; ++i) {
rtp += kRtpHz / k25Fps;
clock.AdvanceTime(k26FpsDelay);
ts_extrapolator.Update(clock.CurrentTime(), rtp);
}
// The camera would normally produce 25 frames in 90K ticks, but is slow
// so takes 1s + k24FpsDelay for 90K ticks.
constexpr Frequency kSlowRtpHz = 90000 / (25 * k26FpsDelay);
// The extrapolator will be predicting that time at millisecond precision.
auto ts = ts_extrapolator.ExtrapolateLocalTime(rtp + kSlowRtpHz.hertz());
ASSERT_TRUE(ts.has_value());
EXPECT_EQ(ts->ms(), clock.TimeInMilliseconds() + 1000);
}
TEST(TimestampExtrapolatorTest, TimestampJump) {
// This simulates a jump in RTP timestamp, which could occur if a camera was
// swapped for example.
SimulatedClock clock(Timestamp::Millis(1337));
TimestampExtrapolator ts_extrapolator(clock.CurrentTime());
uint32_t rtp = 90000;
clock.AdvanceTime(k25FpsDelay);
ts_extrapolator.Update(clock.CurrentTime(), rtp);
rtp += kRtpHz / k25Fps;
clock.AdvanceTime(k25FpsDelay);
ts_extrapolator.Update(clock.CurrentTime(), rtp);
rtp += kRtpHz / k25Fps;
clock.AdvanceTime(k25FpsDelay);
ts_extrapolator.Update(clock.CurrentTime(), rtp);
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp),
Optional(clock.CurrentTime()));
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp + 90000),
Optional(clock.CurrentTime() + TimeDelta::Seconds(1)));
// Jump RTP.
uint32_t new_rtp = 1337 * 90000;
clock.AdvanceTime(k25FpsDelay);
ts_extrapolator.Update(clock.CurrentTime(), new_rtp);
new_rtp += kRtpHz / k25Fps;
clock.AdvanceTime(k25FpsDelay);
ts_extrapolator.Update(clock.CurrentTime(), new_rtp);
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(new_rtp),
Optional(clock.CurrentTime()));
}
TEST(TimestampExtrapolatorTest, GapInReceivedFrames) {
SimulatedClock clock(
Timestamp::Seconds(std::numeric_limits<uint32_t>::max() / 90000 - 31));
TimestampExtrapolator ts_extrapolator(clock.CurrentTime());
uint32_t rtp = std::numeric_limits<uint32_t>::max();
clock.AdvanceTime(k25FpsDelay);
ts_extrapolator.Update(clock.CurrentTime(), rtp);
rtp += 30 * 90000;
clock.AdvanceTime(TimeDelta::Seconds(30));
ts_extrapolator.Update(clock.CurrentTime(), rtp);
EXPECT_THAT(ts_extrapolator.ExtrapolateLocalTime(rtp),
Optional(clock.CurrentTime()));
}
} // namespace webrtc