Instruction manual

HDE-3000 - 67 -
TIFF
The TIFF format is important as one of its variants seems to be the format of
choice for DVD subtitles. The LINK TIFF converter handles non-compressed 256
color “color map” type TIFF files in single or multiple strips. Like PCX, TIFF does not
support alpha, so the converter considers the first entry in the color palette to be the
transparent “color”; all other entrees in the palette are opaque colors. Use the file
converter “TIF2UYC.EXE” to convert these files to “YC” format. Note, this converter
also handles RGB TIFF files in which case the transparent color is C0C0C0.
DVD TIFF files come in two formats: full size and cropped. A full size TIFF file
occupies the entire 720 x 480 pixel plane (720 x 512 for PAL), regardless of how big
the actual subtitle is. A cropped TIFF file is just large enough to hold the subtitle
image. For example, a cropped TIFF file may be 260 pixels wide by 80 pixels high.
Full size TIFF files are normally very wasteful of disk space, and may require more
time to transmit, load, and render on screen. Because of this, LINK has created a
compressed version of the “UYC” format that drastically reduces file size and load
time. This format has the extension “UYC”. Use the file converter “TIF2UYC.EXE”
to convert files to compressed “UYC” format.
YC File Viewer
LINK provides a utility program that enables you to view UYC graphics files on a
PC. This allows users and software developers to inspect files without the need for
HDE-3000 hardware. The program is called “ViewUYC.exe” and runs under
Microsoft Windows. ViewUYC lets you view foreground RGB colors independently
from the alpha channel.
6.8 UYC File Format
Digital Video (SMPTE 125M—4:2:2 Component) information consists of luminance (Y)
and color difference (CR & CB) values. For each line of active video there are 720
luminance values and 360 pairs of color difference values. The information for each line is
transmitted in the following order:
CB0, Y0, CR0, Y1, CB1, Y2, CR1, Y3, ..... CB359, Y718, CR359, Y719
HDE-3000 groups this information into “pixel pairs”. The first pixel pair of a line consists
of the Y values for both pixels (Y0 & Y1) and the CB & CR values for the pixel pair (CB0 &
CR0). The values are each 8 bits and are organized into two 16 bit words (Y0 is the least
significant byte of the Y word and CB0 is the least significant byte of the C word). Alpha
information is also used by HDE-3000 to control the opacity of the overlaid graphics. An 8
bit alpha value is assigned to each pixel and organized into a third 16 bit word (alpha0 is the
least significant byte of the alpha word and aligns with the same pixel as Y0). There are 256
levels of opacity for each pixel. An alpha value of zero is transparent, so the pixel will be
100% background video. An alpha value of 255 is opaque, so the pixel will be 100%
overlay. All of the values in between select levels of semi-transparency for the pixel.
The information for each pixel pair consists of 1 word of Y values, 1 word of color
difference values, and 1 word of alpha values.