1 /*
2  *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 #ifndef WEBRTC_MODULES_RTP_RTCP_SOURCE_TIME_UTIL_H_
12 #define WEBRTC_MODULES_RTP_RTCP_SOURCE_TIME_UTIL_H_
13 
14 #include "webrtc/base/basictypes.h"
15 #include "webrtc/system_wrappers/include/ntp_time.h"
16 
17 namespace webrtc {
18 
19 // Converts NTP timestamp to RTP timestamp.
NtpToRtp(NtpTime ntp,uint32_t freq)20 inline uint32_t NtpToRtp(NtpTime ntp, uint32_t freq) {
21   uint32_t tmp = (static_cast<uint64_t>(ntp.fractions()) * freq) >> 32;
22   return ntp.seconds() * freq + tmp;
23 }
24 // Return the current RTP timestamp from the NTP timestamp
25 // returned by the specified clock.
CurrentRtp(const Clock & clock,uint32_t freq)26 inline uint32_t CurrentRtp(const Clock& clock, uint32_t freq) {
27   return NtpToRtp(NtpTime(clock), freq);
28 }
29 
30 // Helper function for compact ntp representation:
31 // RFC 3550, Section 4. Time Format.
32 // Wallclock time is represented using the timestamp format of
33 // the Network Time Protocol (NTP).
34 // ...
35 // In some fields where a more compact representation is
36 // appropriate, only the middle 32 bits are used; that is, the low 16
37 // bits of the integer part and the high 16 bits of the fractional part.
CompactNtp(NtpTime ntp)38 inline uint32_t CompactNtp(NtpTime ntp) {
39   return (ntp.seconds() << 16) | (ntp.fractions() >> 16);
40 }
41 // Converts interval between compact ntp timestamps to milliseconds.
42 // This interval can be upto ~18.2 hours (2^16 seconds).
CompactNtpIntervalToMs(uint32_t compact_ntp_interval)43 inline uint32_t CompactNtpIntervalToMs(uint32_t compact_ntp_interval) {
44   return static_cast<uint64_t>(compact_ntp_interval) * 1000 / (1 << 16);
45 }
46 
47 }  // namespace webrtc
48 #endif  // WEBRTC_MODULES_RTP_RTCP_SOURCE_TIME_UTIL_H_
49