*nix Documentation Project
·  Home
 +   man pages
·  Linux HOWTOs
·  FreeBSD Tips
·  *niX Forums

  man pages->IRIX man pages -> dmedia/dmGetUST (3d)              


dmGetUST(3dm)							 dmGetUST(3dm)

NAME    [Toc]    [Back]

     dmGetUST, dmGetUSTCurrentTimePair - get digital media Unadjusted System
     Time (UST)

SYNOPSIS    [Toc]    [Back]

     #include <dmedia/dmedia.h>
     Link with -ldmedia

     int dmGetUST(unsigned long	long *ust)
     int dmGetUSTCurrentTimePair(unsigned long long *ust,
				 struct	timeval	*tv)

DESCRIPTION    [Toc]    [Back]

     dmGetUST(3dm) returns a high-resolution, unsigned 64-bit number to
     processes using libdmedia.	The value of UST is the	number of nanoseconds
     since the system was booted. Though the resolution	is 1 nanosecond, the
     actual accuracy may be somewhat lower and varies from system to system.
     Unlike other representations of time under	UNIX, the value	from which
     this timestamp derives is never adjusted; therefore it is guaranteed to
     be	monotonically increasing.

     Typically,	the UST	is used	as a timestamp;	that is, it is paired with a
     specific item or location in a digital media stream. Normally,
     dmGetUST(3dm) is not used to do this; each	medium has its own method for
     obtaining these timestamps. For example, the UST associated with an audio
     sample frame number can be	obtained using the ALgetframetime(3A) call,
     and the UST associated with a video buffer	can be obtained	using the
     vlGetUSTMSCPair(3dm) call.	 In the	MIDI and tserialio libraries, UST
     stamps are	paired with bytes of data which	came in	or will	go out a
     serial port.

     The function dmGetUSTCurrentTimePair(3dm) returns a UST measurement and a
     time of day measurement (see gettimeofday(3)) which represent the same
     instant of	time.  This is often useful for	relating the UST clocks	of two
     different machines.  The usefulness of this function is limited by	the
     reliability of the	UNIX time of day clock,	which (unlike the UST clock)
     can be adjusted by	system administrators and network time daemons.

RETURN VALUE    [Toc]    [Back]

     Both functions return 0 if	successful or -1 on error.

NOTES    [Toc]    [Back]

     Although this function returns an unsigned	64 bit number, most libraries
     which manipulate UST (and MSC where appropriate) use the stamp_t symbol,
     which is defined as a signed 64-bit number.  The signed representation is
     generally more convenient,	since USTs and MSCs are	most often used	in
     signed arithmetic calculations.  We recommend that	you cast the value
     returned by dmGetUST(3dm) directly	into a stamp_t,	as in:
	stamp_t	now;
	dmGetUST((unsigned long	long *)(&now));

									Page 1

dmGetUST(3dm)							 dmGetUST(3dm)

     The period	of the 64-bit unsigned UST clock is 584	years, and the period
     of	the signed 64-bit UST clock is 292 years, so practical code need not
     concern itself with UST wrap in either case.

SEE ALSO    [Toc]    [Back]

     ALintro(3A), ALgetframetime(3A), mdSetOrigin(3dm),	mdSend(3dm),
     mdReceive(3dm), mdIntro(3dm), vlGetUSTMSCPair(3dm), tserialio(3)

									PPPPaaaaggggeeee 2222
[ Back ]
 Similar pages
Name OS Title
dmbufustmsc IRIX get and set unadjusted system time and media stream counter value pair
alGetEventUST IRIX get Unadjusted System Time of audio event
annotator IRIX 3D Annotation with Digital Media Notes
dmSetAudioDefaults IRIX parameters for digital-media audio
dmSetImageDefaults IRIX parameters for digital-media images
dmTCAddTC IRIX digital media timecode mathematics
dmTCFramesBetween IRIX digital media timecode mathematics
dmTCFramesPerDay IRIX digital media timecode mathematics
dmTCToSeconds IRIX digital media timecode mathematics
dmTCToString IRIX digital media timecode mathematics
Copyright © 2004-2005 DeniX Solutions SRL
newsletter delivery service