AL710 Просмотр технического описания (PDF) - AverLogic Technologies Inc

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производитель

AL710

QUAD Video Processor

AverLogic Technologies Inc 

(HLB, VTB)

1/4

screen

AL700/701/710

Full screen

Figure 12: 2X Zoom In Function

In application, Borderline 1 can be turned on first to preview the zooming area on QUAD or

FULL display screen. The previewing window can be moved around by programming

registers (HZOOMSTART, VZOOMSTART), and then change display to ZOOM in mode.

7.8 Overlay Control

AL700/701/710 supports internal and external OSD (On-Screen Display) overlay control. By

embedding SRAM, AL700/701/710 can overlay internal OSD text on top of the video for

the applications like pop-up menu, message text or captions. Also AL700/701/710 can

interface with external OSD chip.

7.8.1 Internal OSD mode

There are 1K-byte Context RAM and 4K-byte Font RAM embedded to support internal

OSD function. Two independent OSD (OSD1 and OSD2) windows are provided and can

be enabled on monitor and/or VCR output respectively. If there is an overlap between

OSD1 and OSD2, the OSD1 will be on the top display layer. The internal OSDs are very

flexible in the way that the font, size, and display location are fully programmable.

There are two kinds of OSD modes supported in the internal OSDs, they are 1-byte mode

and 2-byte mode. The internal Context RAM storages the OSD character codes. The

character codes in the Context RAM would be decoded as the index of the font table in

Font RAM. Also included in the Context RAM is the blinking bit that can enable or

disable the blinking function for the corresponding character. In 2-byte mode, additional

attributes define the foreground and background color information related to the

corresponding character.

The OSD controller will generate OSD key after it reads out the font data. The OSD key

selects the colors to be overlaid on the screen based on the data stored in Context RAM

(in 2-byte mode) or the control registers (in 1-byte mode, #32h<3:0> and #42h<3:0>) that

decide when and where these colors are displayed on the screen. The OSD key is used to

select four out of 16 million (24 bits) OSD colors.

The selected OSD characters and their color data are then passed through the internal

blink control circuits. The blinking frequency is controlled by the BLINKCTRL (register

#21h) with VYSNC as the reference counting clock. The blinking information is stored

as data embedded with character codes stored in Context RAM.

©2001,2002-Copyright by AverLogic Technologies, Corp. Preliminary Version C1.1 22

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