Data Broadcasting using the VBI Data broadcasting is a term used for the point to mulitpoint (‘one to many’) broadcasting of data. Today, radio and broadcasting are the primary means of delivering information electronically to con- sumers. The principal delivery mechanisms for current data broadcasting services include: • FM broadcasting radio channels (FM subcarrier services). • Television broadcast channels via the Vertical Blanking Interval (VBI), sideband or full field (FF). • Cable television broadcast channels via the Vertical Blanking Interval (VBI), sideband or full channel. • Satellite broadcast channels via the Vertical Blanking Interval (VBI), sideband or full channel (C-band, VSAT and Ku-band services). • Telephone networks (fixed or mobile). • Paging channels.

Data broadcasting can use all of a dedicated channel, a portion of an existing radio or television channel, or a portion of a digital channel.

There are a wide choice of platforms for user access systems. Some common examples are:

• Multimedia PCs. • Dedicated TV receivers. • Set Top Boxes.

The following figure shows a block diagram of a databroadcast system using the TV signal VBI or FF to carry data and a Multimedia PC based User Access System.

Insert data Tuner or down converter Philips onto VBI SAA5284

Content Providers’s database Host system

Host data- base User interface Broadcast eg: , HTML Browser via Example USER ACCESS SYSTEM satellite,

cable or

terrestrial

The VBI data would be demodulated and stored in the SAA5284’s on-board 2 kbyte RAM (known as the packet buffer). Every 40 ms1 the host will read this data from the packet buffer (notified by interrupt or polling). Further processing of the packets to reconstruct the original data can then be performed in software on the host CPU.

Philips Semiconductors Multimedia Data Broadcast and Teletext Solutions Philips Semiconductors has been the leading supplier of both hardware and software teletext solutions since the introduction of the service. Philips is now able to offer a full range of devices and software drivers, to integrate teletext and data acquisition with the PC and other multimedia products. Whether your application needs to receive a single page of teletext in order to keep up to date with the latest share prices, requires instant access to a broadcaster’s whole teletext database, or needs to receive other data servies now being created to use the VBI, we can offer a straightforward and easy to use solution.

Hardware solutions Philips Semiconductors offers two families for multimedia data acquisition. The first is based on tradi- tional TV ICs designed to receive European teletext services (625 line ). These devices are page oriented and are not suitable for data stream applications. They require only connec- tions of power, video and I2C to the rest of the system. The I2C bus is used to control the device and read out the acquired data for display via the host system. Software products PCText 1 & 2 are available 1.Depending on number of VBI lines used per field. for PC compatible platforms to source & display teletext data on the PC screen. Several devices are available in this family, from a simple one page decoder to a solution that can hold up to 1000 pages in a separate DRAM. The popular SAA5281 device can receive up to four pages of teletext simultane- ously, and allows the PC to build up a separate page cache four pages at a time.

Philips Semiconductors has recently introduced a new device family which has been designed specifically for the multimedia and PC industry. The SAA5284 is capable of acquiring all the main VBI data standards currently in use. These include European World Standard Teletext (WST), US WST, North American Basic Teletext Standard (NABTS, used by recent PC industry format proposals), Video Programming System (VPS), Wide Screen Signalling System (WSS), US Closed Captioning, Chinese teletext, Japanese teletext, and the device is even programmable to allow for new data framing code formats.

SAA5284 is a mixed signal full custom IC. It takes analogue baseband video (CVBS) input on one of two register selectable inputs. Multiple standards of video data from selectable VBI lines or from the whole field are acquired and stored in the on-board 2 kbyte SRAM (or packet buffer). This data is then accessible via a multistandard parallel interface, I2C or a digital video interface. Interrupt and DMA support are provided.

When designing the SAA5284, the architectural split of the processing of VBI data between hardware and software (running on the host CPU) was analysed at length. The result is that flexibility in processing acquired VBI data is maintained, as this is done mainly in host CPU software. Meanwhile, all data acquisition and caching functions are carried out on the IC to minimise loading on the host CPU. Data demodulation is performed in hardware by a dedicated adaptive digital filter. This maximises data demodulation performance in the presence of distortion and noise on the TV signal.

This hardware/software divide is fully exploited by a range of PC drivers and funtional software modules available for use with SAA5284. These include VxDs and DLLs to perform many functions.

The following figure shows an application circuit for using the SAA5284 in a typical PC ISA add-in card

type of application. .

+5 VA +5 VD

16 41 6

D7 20 VDDX VDDA VDDD D6 21 7 0VA 100n 22 12 BLACK D5 D4 23 13 24 27 k IREF D3 75R 25 D2 15 26 CVBS0 CVBS0 D1 100n 27 14 CVBS1 D0 CVBS1 0 D<7..0> 100n 8 28 OSCIN A0 A0 SAA5284 29 22p 12 MHz* A1 A1 75R 7 30 OSCOUT A2 A2 31 22p 9 INT IRQx OSCGND 32 0VA RDY I/O RDY 33 3 SDA WR IOW 4 SCL 34 RD IOR 2 36 HREF DMARQ DRQx ** 42 LLC 43 DMACK 37 LLC2 1 39 VPOIN1 RESET RESET 38 5 ** need only be VPOIN0 DENB n/c connected if 35 DMA used, else 0VD CS0 connect to +5VD VSSA VSSD VSSD VSSD SEL1 SEL0 CS1 17 40 18 19 11 10 44 * Option of 13.5, 15 and 16 Mhz 11 or direct feed from external clock B1 B0 9 0VA 0VD DACKx ** address decode eg: 1 PLUS153 or I0 AEN 74 series logic I1 2 3 supply decoupling I2 3 19 B9 B8 I3 4 18 5 5VA 5VD 17 B7 I4 +5 V B6 I5 6 16 7 n/c 15 B5 I6 B4 8 100n µ 14 I7 2 2 13 B3 12 B2 9 100n 2µ2 GND Vcc A<9..3> 10 20 0V 0VA 0VD 0VD 5VD

Figure 01 Application Circuit Diagram for ISA Card

PCText PCText is a family of software drivers designed to support the user friendly access of WST on a PC. All versions of the driver are delivered as WindowsTM Dynamic Linked Libraries which are compatible with both Windows 3.1 TM and Windows 95TM. The libraries provide a high level interface to the teletext sys- tem, which avoids the software developer having to know anything about the WST spec. The User Inter- face software merely asks the driver for a page of teletext, and the driver then draws the page without further commands being needed. All versions support Fastext, copying the page as ascii text or a bit- map, printing the page and can support multiple teletext viewers simultaneously. When used with a SAA5249, SAA5254 or SAA5281, the software communicates via I2C (driver not included). Up to 30 pages can be cached for instant access. PCText2 adds a scaleable truetype TM font, Table Of Pages and embeded page requests, whilst main- taining a superset of the PCText1 function interface. PCText3 accesses the SAA5284 via a parallel interface, and has extensions to the high level API. This version can be configured to use allocated system memory to store as many broadcast pages as desired. This offers the opportunity to implement a true ‘instant access’ teletext system, where the PC holds a complete, up to date copy of the broadcast database. All three versions of the PCText driver are availabel under license from Philips Semiconductors.

PCText 1 PCText 2 PCText 3

No Knowledge Of Teletext Needed to use driver X X X Level One Teletext decoding and display X X X Western European Language Coverage X X X Fastext Support X X X Table Of Pages X X Text & Bitmap, Save, Print and Copy Support X X X Easy Interfacing To C, C++, Visual Basic, Delphi X X X Supplied as Windows DLL’s X X X Scaleable Font X X Embedded Hyperlink Page Numbers X X Intelligent Pre Acquisition X X X Fixed Side 30 page cache X X User defined page cache X Supports SAA5246, 5249, 5254, 5281 X X Supports SAA5284 X Available Now Now May 97