dmGetUST man page on IRIX

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dmGetUST(3dm)							 dmGetUST(3dm)

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

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

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

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

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

									Page 2

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