ITK Release 4/Video/Time Stamp: Difference between revisions

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** seconds, hours, days
** seconds, hours, days
* Have convenience methods for computing differences between two times
* Have convenience methods for computing differences between two times
* Encapsulated type:
** External time representation = double in microseconds
** Internal time representation is private and is not exposed

Revision as of 14:33, 29 November 2010

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

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 (before losing any precision)
    • 2^53 / ( 1000000 * 3600 * 24.0 * 365 ) = 285
    • after that it will be counting in tens of microseconds...
  • 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
  • Encapsulated type:
    • External time representation = double in microseconds
    • Internal time representation is private and is not exposed
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