Difference between revisions of "OpenIGTLink/Timestamp"
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Revision as of 19:24, 10 January 2008
Home < OpenIGTLink < Timestamp
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
- 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:
- Install NTP on all devices
- 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
