mdSetStampMode(3dm)					   mdSetStampMode(3dm)

NAME    [Toc]    [Back]

     mdGetStampMode, mdSetStampMode - control time stamping for	an MDport

SYNOPSIS    [Toc]    [Back]

     #include <dmedia/midi.h>

     int mdSetStampMode(MDport port, int mode)

     int mdGetStampMode(MDport port)

DESCRIPTION    [Toc]    [Back]

     mdSetStampMode controls the interpretation	of the stamp field in an
     MDevent by	the port.  The available interpretation	modes are MD_NOSTAMP,
     MD_DELTASTAMP, MD_RELATIVESTAMP, MD_RELATIVETICKS and MD_DELTATICKS.

     If	an output port is in MD_NOSTAMP	mode, the interface will ignore	the
     stamp and transmit	the event immediately. On input, events	are stamped
     with the UST (unadjusted system time) corresponding to the	arrival	time
     of	the final byte in the message.

     In	MD_DELTASTAMP mode, the	stamp contains the number of nanoseconds
     between the event and its predecessor.  If	the stamp is 0,	the two	events
     are logically coincident in time.	On output, if the stamp	is non-zero,
     the event will be transmitted the specified number	of nanoseconds after
     the preceeding event.

     In	MD_RELATIVESTAMP mode, stamps are relative to the port's origin	time
     (see mdSetStartPoint(3dm)).  A time stamp of 0 indicates that the event
     was received or transmitted at the	origin UST.  If	an event with a	stamp
     of	n is sent to an	interface in this mode,	the driver will	transmit the
     event n nanoseconds after the origin time.	 If the	application falls
     behind and	transmits events whose stamps indicate that the	event should
     have been sent sometime in	the past, the event will be transmitted
     immediately.  If an event with a stamp of n is received, then the last
     byte of the event arrived n nanoseconds after the origin time.

     MD_RELATIVETICKS and MD_DELTATICKS	set the	MDport into a mode that	allows
     the use of	ticks instead of real time to control the timing of MIDI
     events.  Ticks are	defined	in terms compatible with Standard MIDI files;
     at	any given point, the duration of a tick	is equal to the	number of
     microseconds per quarter note (as set by mdSetTempo or a tempo event)
     multiplied	by the current tempo scaling value (set	with mdSetTemposcale)
     and divided by the	current	number of divisions (set with mdSetDivision).
     The advantage of this mode	is that	the duration of	each beat can be
     changed (either synchronously with	a tempo	event or asynchronously	with
     mdSetTempoScale) without altering the stamps on the events.
     MD_RELATIVETICKS allows the ticks to be reckoned from an origin tick that
     is	set with mdSetStartPoint(3A).  MD_DELTATICKS uses simple delta ticks,
     where the stamp's value indicates how many	ticks fall between this	event
     and the time at which its predecessor was transmitted.





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mdSetStampMode(3dm)					   mdSetStampMode(3dm)

DIAGNOSTICS    [Toc]    [Back]

     An	application should set the stamping mode immediately after a port is
     opened.  Once set,	the stamping mode should not be	changed	again.

RETURN VALUE    [Toc]    [Back]

     mdGetStampMode returns the	current	stamp mode for the port.
     mdSetStampMode returns 0 on success and -1	on error.  The following error
     codes are expected:

     EINVAL   -	An undefined stamp mode	was specified.

SEE ALSO    [Toc]    [Back]

     mdSetTempo(3dm), mdSetTemposcale(3dm), mdSetDivision(3dm)


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