Datasheet

Functional Description
R
Datasheet 193
5.4.8.3 Sub-picture Support
Sub-picture is used for two purposes: Subtitles for movie captions, which are superimposed on a
main picture, and for menus to provide some visual operation environments for the user.
DVD allows movie subtitles to be recorded as sub-pictures. On a DVD disc, it is called “Subtitle”
because it has been prepared for storing captions. Since the disc can have a maximum of 32 tracks
for Subtitles, they can be used for various applications, for example, as Subtitles in different
languages.
There are two kinds of menus, the system menus and other In-Title menus. First, the system
menus are displayed and operated at startup of or during the playback of the disc or from the stop
state. Second, In-Title menus can be programmed as a combination of sub-picture and highlight
commands to be displayed during playback of the disc.
The GMCH supports sub-picture for DVD and DBS by mixing the two video streams via alpha
blending. Unlike color keying, alpha blending provides a softer effect and each pixel that is
displayed is a composite between the two video stream pixels. The GMCH can utilize four
methods when dealing with sub-pictures. This flexibility means that the GMCH can work with all
sub-picture formats.
5.5 Display Interface
The GMCH has four dedicated display interfaces, the analog port, the LFP LVDS interface, and
the DVO B/C interface. The DVO B and DVO C interface can support TV-out encoders, external
DACs, LVDS transmitters, and TMDS transmitters. Each display port has control signals that
may be used to control, configure and/or determine the capabilities of an external device. The data
that is sent out the display port is selected from one of the two possible sources; display pipe A or
display pipe B.
5.5.1 Analog Display Port Characteristics
The analog display port provides a RGB signal output along with a HSYNC and VSYNC signal.
There is an associated DDC signal pair that is implemented using GPIO pins dedicated to the
analog port. The intended target device is for a CRT based monitor with a VGA connector.
5.5.1.1 Integrated RAMDAC
The display function contains a 350 MHz integrated 24-bit RAM-based Digital-to-Analog
Converter (RAMDAC) that transforms up to 2048 x 1536 digital pixels from the graphics and
video subsystems to a maximum pixel analog data for the CRT monitor at a maximum refresh rate
of 75-Hz for the Intel 852GME GMCH. Three, 8-bit DACs provide the R, G, and B signals to the
monitor.
5.5.1.2 DDC (Display Data Channel)
DDC is defined by VESA. Its purpose is to allow communication between the host system and
display. Both configuration and control information can be exchanged allowing plug-and-play
systems to be realized. Support for DDC 1 and 2 is implemented.