Subtitle Files - Ultech Corporation DV2000 User Manual

5.3 Subtitle Files

There are two ways for character generators to display text on screen. The "traditional"
method involves sending commands and text to the character generator by way of a serial
communications port. The CG interprets the commands and turns the text strings into on-
screen characters. The CG renders the characters in real time based on attributes you have
specified, such as color, font, and position. A future version of DV2000 software will
provide this capability—the command set will be backwards compatible with ULTECH's
SG401 analog subtitle/character generator.
A more modern way of generating text on screen is to create the subtitles off-line in the form
of bit-mapped images. Each subtitle becomes an individual bit-mapped image file. The
advantage of this approach is that the CG does not have to deal with fonts, nor does it have
to deal with rules involving the conversion of commands and text strings into on-screen
characters. With this method, subtitles are created on a PC using any font installed on the
PC. You can see on the PC's monitor how the subtitle will look when displayed on a TV
screen.
Subtitling using the bit-mapped method involves two sets of files: a single subtitle "script"
file and a series of bit-mapped files, one for each subtitle. In the DVD world, subtitle script
files are known as "navigation" files. The DV2000 uses a simple file format that is opti-
mized for subtitling. Files in this format have a file extension of ".usf", and are therefore
referred to as "USF" files, or simply "subtitle files".
.USF File Format
ULTECH subtitle script files contain a single command, subtitle. The command takes the
parameters time code, and optionally, filename, x position and y position. The first parameter
is the time that the file is to appear on the display. If the filename is omitted, then the display
is erased at the time code. Thus a subtitle command with a time code and a filename means
"display this graphic file at time t at position x,y"; and a subtitle command with only a time
code means "erase whatever is on the display at time t". Note: The commands should appear
in chronological order in the file.
Example:
SUBTITLE 00:01:00:09 nine.uyc 0 0
SUBTITLE 00:01:00:10 ten.uyc
SUBTITLE 00:01:00:11
This example displays the bitmap nine.uyc in position 0,0 at time code one hour and nine
seconds, at time code one hour and ten seconds ten.uyc is displayed, and finally at one hour
and eleven seconds the display is erased. This specialized command makes the creation and
reading of subtitle files easy and intuitive.
The subtitle application reads bit mapped graphics files in ULTECH's ".uyc" format. The
following section discusses this format in detail.
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