Grab Constant Spaced Sequence
Grab Constant Spaced Sequence
Under this option DigImage is able to efficiently acquire a series of
buffers at a constant spacing, grabbing as rapidly as every complete frame
(two fields). If N images are to be grabbed, then the first image will be
placed in buffer N and the last in buffer 1. Images will be grabbed to the
onboard frame buffers in groups of up to 4 or 16 (for the DT2862 or DT2861,
respectively), and transferred to extended memory as required. Note
however, that if the images are separated by more than about 1s, then it
will be more efficient to use the 'T Grab frames at specific times'
facility.
Start time (offset) ?
This entry specifies the time, relative to the current time, at which the
first buffer will be acquired. The time is specified using the normal
DigImage time format of minutes:seconds (see the <shift><f1> general help
option for more details).
Sample spacing (even number of fields) ?
The spacing of the images is specified in terms of the individual video
fields. As DigImage deals with complete frames consisting of the even and
odd fields, the Sample spacing should be specified as an even number of
fields (each field is 1/50s or 1/60 for PAL or NTSC, respectively). If an
odd number is specified, then a spacing of one less than this value is
used. The maximum spacing is 1s (50 or 60 fields).
Number of buffers to acquire ?
Between one and one less than the total number of buffers available to
DigImage may be acquired using this operation. If N buffers are specified,
then the first image is placed in buffer N, the second in buffer N-1 and
the last in buffer 1.
On completion Reposition tape or Leave ?
The answer to this question specifies the action to be taken once all the
frames have been acquired. The video tape may be either repositioned (R) to
the starting point of the sequence, or left (L) where it is after the last
frame has been grabbed.
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DigImage User Documentation
Stuart Dalziel,
last page update: 19 February 1996