ITK Release 4/Video/Time Stamp

Reference Systems

VRPN - UNC

URL

http://www.cs.unc.edu/Research/vrpn/vrpn_getting_started.html

Time Stamp Structure

<source lang="cpp"> struct timeval

 {
   __time_t tv_sec;		/* Seconds.  */
   __suseconds_t tv_usec;	/* Microseconds.  */
 };

</source>

OpenCV

• include/opencv/cv.h: double timestamp
• src/cv/_cvipp.h: float timestamp
• 3rdparty/include/ffmpeg_/avformat.h: int64_t timestamp;

KWSys

• static double GetTime();

ITK RealTimeClock

• itkRealTimeClock.h
• itkRealTimeClock.cxx

System Time

• http://en.wikipedia.org/wiki/System_time

Scales

• int32 : can count in microseconds, up to 4.5 years
  • 2**32 / (30 * 3600 * 24.0 * 365 ) = 4.5 years

• double : can count in microseconds, up to 285 years
  • 2^53 / ( 1000000 * 3600 * 24.0 * 365 ) = 285

• int64 : can count in microseconds, up to 584942 years
  • 2**64 / ( 1000000 * 3600 * 24.0 * 365 ) = 584942
  • (or in nanoseconds up to 584 years)

Units

• Should the time units be specified ?
  • Use microseconds ?

Proposal

• Use double as internal representation
• Use micro-seconds as unit
• Have convenience methods to return time in other units
  • seconds, hours, days
• Have convenience methods for computing differences between two times