blob: dedba4d7ec1d65b3d65dabbb8cc89089616a461a [file] [log] [blame]
* 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 "webrtc/modules/rtp_rtcp/source/time_util.h"
#include <algorithm>
namespace webrtc {
namespace {
// TODO(danilchap): Make generic, optimize and move to base.
inline int64_t DivideRoundToNearest(int64_t x, uint32_t y) {
// Caller ensure x is positive by converting unsigned value into it.
// So this Divide doesn't need to handle negative argument case.
return (x + y / 2) / y;
} // namespace
int64_t CompactNtpRttToMs(uint32_t compact_ntp_interval) {
// 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 are less likely than non-monotonic ntp clock,
// those values consider to be negative and convert to minimum value of 1ms.
if (compact_ntp_interval > 0x80000000)
return 1;
// Convert to 64bit value to avoid multiplication overflow.
int64_t value = static_cast<int64_t>(compact_ntp_interval);
// To convert to milliseconds need to divide by 2^16 to get seconds,
// then multiply by 1000 to get milliseconds. To avoid float operations,
// multiplication and division swapped.
int64_t ms = DivideRoundToNearest(value * 1000, 1 << 16);
// Rtt value 0 considered too good to be true and increases to 1.
return std::max<int64_t>(ms, 1);
} // namespace webrtc