Grass Valley Switcher Products - Manual (Page 145)

Switcher Products — Protocols Manual 145
Image Metadata File Format
Mark In/Out
When an animation is captured, extraneous material before or after the
desired segment is often included. The mark in and out points instruct the
still store to start and end playback at specific points. The frames prior to
the in point and after the out point are not played.
Note that the still store actually plays up to the frame before the mark out
frame number. The mark out frame is not played.
Loops
Animations often are repetitive in nature. That is, the entire animation (or
a portion of it) repeats. In order to save storage space, the still store permits
these repeated regions to be included only once in an animation file. Meta-
data instructions control where a loop repeat occurs and how many times
that segment is repeated.
The loopFrom point is the last frame in a looped region. The loopTo point
is the first frame in a looped region. The loopCount is the number of times
the segment is repeated. When the animation begins playback, it starts at
the mark in point and plays to the loop from point. If a repeat is enabled,
playback then jumps to the loopTo frame number and continues playback.
The number of times loopFrom is encountered is monitored. When this
count matches loopCount, the still store does not jump back to the loopTo
point and plays to the mark out point. A special case of loopCount (-1)
allows the loop region to repeat forever.
Note that loopFrom is normally after loopTo. If loopTo is set after loop-
From, and loopCount is not zero, the still store will jump from the loop-
From point to the loopTo point then play to the mark out point. No repeats
occur, but the material between loopFrom and loopTo is skipped.
Key Offset
Video + key images are often captured in two passes, one for the video and
one for the key. For animations, temporal alignment of the video and key
components may be difficult in a two-pass capture. The keyOffset param-
eter allows the timing of the key signal to be slipped relative to the video so
that the two play back in sync even if they are captured out of sync.
Animations that are generated rather than captured will probably not have
video to key sync problems and will not need to adjust key offset. But the
key offset may need to be considered when importing still store animations
that were captured on the still store.
This parameter is not currently implemented, and should be set to 0. This
means at this time the video and key portions of a video plus key animation
must be temporally aligned.