Specification > Timestamp

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Timestamp field summary

• Big Endian format: bits numbered in big-endian fashion from 0 starting at the left, or high-order, position.
• Seconds and fraction of seconds: timestamps are represented as a 64-bit unsigned fixed-point number, in seconds relative to 00:00:00 January 1, 1970, UTC. The integer part is in the first 32 bits (Unix-style timestamp) and the fraction part in the last 32 bits. In the fraction part, the non-significant low order can be set to 0.
• Wrap around: The first 32-bit field will overflow some time in 2106 (second 4,294,967,296)

Obtaining timestamp

• itk::RealTimeClock
• Linux / Mac: ftime()
• Windows: ftime() - 10 ms resolution
• Old Timestamp - 1 sec resoultion: Now, Time, Timer
• System time - 10 msec resolution: GetTickCount, GetTickCount64 or timeGetTime()
• Highres - hardware dependent: QueryPerformanceCounter (Intel IA32 instruction: RDTSC)

Time synchronization

Two solutions:

1. Install NTP on all devices
2. Compute timestamp differences (local NTP can be used)

Resources

• NTP4 Timestamp: RFC 2030 and RFC 1305. (See “3. NTP Timestamp Format”)
• Obtaining Accurate Timestamps under Windows XP