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Appendix
Data Capture
Text memory 10 pages
Inventory of transmitted Teletext pages stored in the Transmitted Page Table (TPT) and Subtitle Page
Table (SPT)
Data Capture for US Closed Caption
Data Capture for 525/625 line WST, VPS (PDC system A) and Wide Screen Signalling (WSS) bit
decoding Automatic selection between 525 WST/625 WST
Automatic selection between 625 WST/VPS on line 16 of VBI
Real-time capture and decoding for WST Teletext in Hardware, to enable optimised -processor
throughput
Automatic detection of FASTEXT transmission
Real-time packet 26 engine in Hardware for processing accented, G2 and G3 characters
Signal quality detector for video and WST/VPS data types
Comprehensive teletext language coverage
Full Field and Vertical Blanking lnterval (VBI) data capture of WST data
Display
Teletext and Enhanced OSD modes
Features of lever 1.5 WST and US Close Caption
Serial and Parallel Display Attributes
Single/Double/Quadruple Width and Height for characters
Scrolling of display region
Variable flash rate controlled by software
Enhanced display features including overlining, underlining and italics
Soft colours using CLUT with 4096 colour palette
Globally selectable scan lines per row (9/10/13/16) and character matrix [12x10, 12xl3, 12x16 (VxH)]
Fringing (Shadow) selectable from N-S-E-W direction
Fringe colour selectable
Meshing of defined area
Contrast reduction of defined area
Cursor
Special Graphics Characters with two planes, allowing four colours per character
32 software redefinable On-Screen display characters
4 WST Character sets (GO/G2) in single device (e.g. Latin, Cyrillic, Greek, Arabic)
G1 Mosaic graphics, Limited G3 Line drawing characters
WST Character sets and Closed Caption Character set in single device
Data Capture
The Data Capture section takes in the analogue Composite Vidéo and Blanking Signal (CVBS), and from
this extracts the required data, which is then decoded and stored in memory.
The extraction of the data is performed in the digital domain. The first stage is to convert the analogue
CVBS signal into a digital form. This is done using an ADC sampling at 12MHz. The data and clock
recovery is then performed by a Multi-Rate Video Input Processor (MuIVIP). From the recovered data
and clock the following data types are extracted WST Teletext (625/525), Closed Caption, VPS, WSS.
The extracted data is stored in either memory (DRAM) via the Memory Interface or in SFR locations.
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Service manual WP-795
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