PC 98 Television Output Requirements

This section summarizes the key design issues and requirements for television output capabilities, which are recommended for all PC 98 system types and required for any Entertainment PC 98 system that does not include a large-screen entertainment monitor.

The requirements in this section apply only if the television output capability is present on a PC 98 system or on a graphics adapter that supports television output capabilities. Some television output capabilities listed in this section are required for Entertainment PC 98 only.

The required support allows an NTSC or PAL television to be used as a primary or secondary display surface for the Windows operating system and for Windows-based applications. Such a display surface allows more realistic game, video, and multimedia experiences for users who want to use a large-screen television that they already own.

If television output capabilities are provided in a PC 98 system, support is required for either NTSC or PAL standards. NTSC refers to the television standards first developed in the United States and used in Canada, Japan, and Mexico. PAL refers to the television standards first developed in Germany and used in Austria, Belgium Brazil, Denmark, Finland, the Netherlands, Norway, Sweden, Switzerland, and the United Kingdom.

For more information about world television standards, see the web site at http://www.bbc.co.uk/aberdeen/eng_info/.

31. Adapter supports both NTSC and PAL output

It is recommended that the television output adapter supports both output standards. If NTSC is supported, then the NTSC system must support 640 × 400 and 640 × 480 at 60 Hz. If PAL is supported, then the PAL system must support 640 × 480 and 800 × 600 at 50 Hz.

Whether either or both output standards are supported, software must be capable of independently enabling and disabling television and VGA output.

Note: For NTSC, the 60-Hz mode described in this section is actually 59.940 Hz.

32. Default boot mode supports appropriate locale

PC 98 systems and graphics adapters must enable television output automatically as the primary display if a VGA monitor is not attached, defaulting to modes compatible with television output in the geographic region for which the adapter was localized. NTSC adapters should default to 60-Hz modes; PAL adapters should default to 50-Hz modes. Ideally, an adapter would support both modes and provide a safe means for the default selection to be changed by a user.

33. Adapter supports underscan scaling

For Consumer PC 98 and Entertainment PC 98 systems, the television output adapter must be able to correct horizontal and vertical overscan using hardware scaling. This allows 640 × 480 resolution modes to fit onto NTSC displays and 800 × 600 resolution modes to fit onto PAL displays.

Driver software must be capable of enabling and disabling scaling and also of adjusting scaling for compatibility with a variety of television monitors. As television monitors age, overscan reduces, so less scaling is required.

34. Adapter supports flicker filter

The television output adapter must use multi-line (3-tap minimum) hardware filtering techniques for flicker reduction. Enable, disable, and adjust capabilities for the flicker filter must be software controllable. Also, overscan should be software-enabled when the PC is playing full-screen video.

35. Adapter provides proper termination

Proper termination is required so that optimal picture quality from any connector does not require displays to be attached to other connectors. For example, a VGA monitor must not be required in order for the S-Video output to appear properly.

36. Adapter supports RCA-style composite video and S-Video connectors

Compared to RCA-style composite video, S-Video dramatically improves the picture quality of the NTSC or PAL scan converter. This standard is designed to reduce cross talk between chrominance and luminance signals and to increase the luminance bandwidth capability of the television. For a description of this standard, see http://www.bbc.co.uk/aberdeen/eng_info/.

A Solent Club for Amateur Radio and Television (SCART; also called Peritel) connector can be supported for European markets, but is not required for North American markets. Notice that most European television sets have two SCART sockets. One allows stereo audio and composite video I/O switchable to RGB inputs. The other supports switching from composite input to S-Video input. The first can be used to connect a satellite receiver for RGB capability. The other can be used to connect a VCR using S-Video for television output. A camcorder usually has connections for composite video, stereo audio, and S-Video. For a description of the SCART standard, see the web site at http://www.bbc.co.uk/aberdeen/eng_info/.

37. Adapter supports both VGA and television output

Recommended: Simultaneous output to VGA monitor and television.

In addition to television output, the PC 98 system also must support VGA output to ensure that users with existing large-screen VGA monitors can use this output capability.

38. Software supports positioning

Software must be able to program the television output hardware to position the television image in increments of 4 pixels horizontally and 4 scan lines vertically.

39. Software supports detection of television connection

For Consumer PC 98 and Entertainment PC 98 systems, software must be able to read the television output hardware to detect whether a television is attached to S-Video or composite output connectors. (Detection of a VGA monitor is achieved using the separate DDC requirement for graphics adapters and monitors.)

This is required to allow the operating system and graphics drivers to correctly support display output during the startup sequence (for example, determining what resolution and refresh rate to use) and to allow the applications to adjust their user interfaces appropriately to the screen capabilities.