Grass Valley Switcher Products - Manual (Page 132)

132 Switcher Products — Protocols Manual
Section 6 — Still Store Image File Format
Kalypso and Zodiak still store systems use a pair of files to describe an
image rather than embedding information about the image into a single
file. Since FTP is the primary interface to the still store, it is not possible to
transfer part of a file. A separate “metadata” file provides rapid access to
information about the image without transferring the image itself.
Still store “images” refer to one of the following:
• Video only still
• Video plus key still
• Video only animation
• Video plus key animation
In many cases, the still store supplies small, animated icons or bugs. To
increase efficiency, images do not have to be a full television frame. During
the capture process, the image can be “fenced” to a 1/2 x 1/2, 1/3 x 1/3, or
1/5 x 1/5 of the full size image. Only the fenced region is written to the file.
On Zodiak systems, the animation and fencing features were implemented
in Zodiak Release 3 software. Earlier Zodiak software versions supported
only full size still images.
Each image has an identifier handle. This handle must be unique within a
directory from which the still store loads images. A DOS standard 8.3 file
name and extension express the image handle and bind the data and meta-
data files together. A separate image name (stored in the metadata file) is
used for display purposes.
Image files names have a specific format:
• Metadata files are of the form I000nnnn.gva
• Data files are of the form I000nnnn.gvi
The first four characters are the letter I followed by three zeros.
The last four characters represent the image handle: a number between
0001 and 2000 (0001 – 0050 for Zodiak version 2). Leading zeros must be
included. The still store matches image and metadata files according to
their file names. If the information contained in the file pair disagree, the
image will not load properly. The metadata file has space for the image
handle, but this field is unused. The image handle contained in the file
name is sufficient to identify the image.
In order to create a still store image, the application must be able to convert
the graphics data into CCIR 601, SMPTE 274M, or SMPTE 296M format,
pack it in the proper order and write it to the data file. It also must generate
a metadata file that accurately describes the contents of the matching data
file. The metadata file of an existing image also holds the key to unpack the
matching image data should the application wish to ingest an image
created by the still store.