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/*
* Copyright (c) 2016 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/rtp_rtcp/source/ntp_time_util.h"
#include <algorithm>
#include <cstdint>
#include "api/units/time_delta.h"
#include "rtc_base/numerics/divide_round.h"
#include "rtc_base/time_utils.h"
namespace webrtc {
uint32_t SaturatedToCompactNtp(TimeDelta delta) {
constexpr uint32_t kMaxCompactNtp = 0xFFFFFFFF;
constexpr int kCompactNtpInSecond = 0x10000;
if (delta <= TimeDelta::Zero())
return 0;
if (delta.us() >= kMaxCompactNtp * kNumMicrosecsPerSec / kCompactNtpInSecond)
return kMaxCompactNtp;
// To convert to compact ntp need to divide by 1e6 to get seconds,
// then multiply by 0x10000 to get the final result.
// To avoid float operations, multiplication and division swapped.
return DivideRoundToNearest(delta.us() * kCompactNtpInSecond,
kNumMicrosecsPerSec);
}
TimeDelta CompactNtpIntervalToTimeDelta(uint32_t compact_ntp_interval) {
// Convert to 64bit value to avoid multiplication overflow.
int64_t value = int64_t{compact_ntp_interval};
if (compact_ntp_interval > 0x8000'0000) {
value -= (int64_t{1} << 32);
}
// To convert to TimeDelta need to divide by 2^16 to get seconds,
// then multiply by 1'000'000 to get microseconds. To avoid float operations,
// multiplication and division are swapped.
int64_t us = DivideRoundToNearest(value * kNumMicrosecsPerSec, 1 << 16);
return TimeDelta::Micros(us);
}
TimeDelta CompactNtpRttToTimeDelta(uint32_t compact_ntp_interval) {
static constexpr TimeDelta kMinRtt = TimeDelta::Millis(1);
// Interval to convert expected to be positive, e.g. RTT or delay.
// Because interval can be derived from non-monotonic ntp clock,
// it might become negative that is indistinguishable from very large values.
// Since very large RTT/delay is less likely than non-monotonic ntp clock,
// such value is considered negative and converted to minimum value of 1ms.
// Small RTT value is considered too good to be true and increased to 1ms.
return std::max(CompactNtpIntervalToTimeDelta(compact_ntp_interval), kMinRtt);
}
} // namespace webrtc
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