VELREP(OPCS)		Optical Printer Control System		VELREP(OPCS)

NAME
    velrep - special purpose velocity repeat patterns for tandem shooting

USAGE
    velrep [filename] [repcnt]

	'filename' is the name of a '.vrp' file (format described
	below) that contains the commands to define the velocities 
	necessary for tandem shooting.

	'repcnt' is the number of times to loop the velocity
	patterns defined in the .vrp file.

DESCRIPTION
    This command lets advanced users define very specific velocity patterns
    to send to the motors for precise tandem-motor shooting, such as shooting
    YCM B & W separation masters at full speed.

    Basically, any situation where shooting with separate cam and pro commands
    is too slow.

    The .vrp file defines which motors will be running.

    Normally this command is not executed directly by camera operators;
    typically a custom OPCS 'runcmd' command is defined to invoke velrep
    to implement shooting operations. This way, the runcmd programmer
    can hide the filename, which the camera operator shouldn't have to
    deal with.
    
    For instance, one might define a 'ycmshoot' command in the
    OPCSDEFS.OPC file as:

        runcmd ycm ycm.run 1

    ..and creating a one-line 'ycm.run' file that contains:

        @velrep ycm.vrp $1

    Then the operator can just type 'ycm 10', and this will invoke the
    more obscure command 'velrep ycm.vrp 10' behind the scenes.

EXAMPLE
    velrep campro.vrp 5 # repeat the campro.vrp pattern 5 times

THE .VRP FILE FORMAT

<label>:		# text label used to identify blocks of vels
0	0	0	# vels, one for each channel (a, b, c..)
-10	0	0	# '-' prefix indicates run in reverse
10+	10+	10+	# '+' postfix indicates increment/decrement the 
                        #     frame counter by 1. Inc or dec depends on the
			#     vel's direction; 10+ will inc, -10+ will dec.
0!	0	0	# '!' postfix (in 'a' chan ONLY) does 'allstop check'
                        #     (if true, jumps to <label> for 'allstop <label>')
                        #     'allstop <label>' must be defined if ! specified.
			#     Check is done AFTER these vels are sent to motors.
goto <label>		# where to go next after last vels sent
repeat <label>	        # if repeating, go to <label>
allstop <label>	        # if allstop occurs, jumps to <label> to stop the motors
                        # Only one 'allstop <label>' allowed in entire file.
			# '!' postfix indicates where to do the allstop check.
tension +1 +1 -1 ..     # Sets directions motors are primarily running,
                        # either +1 (fwd), -1(rev), or 0 (still) for each chan.
done			# return to OPCS, shooting completed

    o Lines whose first character starts with a '#' are ignored.
      These are comment lines,  and are not parsed by velrep.

    o Each line should have no more than 256 characters.

    o Always checks for BUCKLE and VIEWER as part of allstop checking.


FUTURE
    o Add a way to specify BUCKLE/VIEWER/TRIP checks in the .vrp file.

ORIGIN
    Gregory Ercolano, Altadena, California 12/15/03