MPEG-2 Playback Requirements

The requirements in this section apply for MPEG-2 decoders. All requirements apply for both software and hardware decoders or any combination of both unless otherwise noted in a specific requirement. The requirements in this section apply for devices that support playback of an MPEG-2 stream from any source, including DVD, digital or broadcast satellite systems, ATSC DTV, hard drives, and so on.

Any PC 98 system that includes the ability to play back MPEG-2 must meet the requirements listed here to ensure quality playback of MPEG-2 data. A PC with an MPEG-2 playback application and MPEG-2 decoder is an example of a system that must meet these requirements.

For example, an Office PC 98 system that includes a DVD-ROM drive for storage purposes but does not include DVD-Video playback software is exempt from these requirements but must warn users that the feature is not supported.

For decoder driver requirements, see the “Device Drivers and Installation for Video and Broadcast Components” section later in this chapter. For related MPEG-2 audio playback requirements, see the “Audio Components” chapter in Part 4 of this guide.

Important: An MPEG-2 hardware decoder must meet the PC 98 requirements for bus mastering. If a hardware solution is implemented that is not integrated in the graphics accelerator, a video port must also be included as part of the video subsystem, as defined in the “System Requirements for Video and Broadcast Components” section earlier in this chapter.

11. System warns users if it cannot play DVD movies

Consumer PC 98 Office PC 98 Entertainment PC 98

Required Required if no DVD-Video Required

An Office PC 98 system that includes a DVD-ROM drive used only for storage purposes must warn end users that DVD-Video playback is not supported whenever such media is inserted in the drive. All system types that support playback of DVD-Video discs must warn users if a DVD-Video disc from another region is inserted in the drive.

12. MPEG-2 playback meets PC 98 requirements

Consumer PC 98 Office PC 98 Entertainment PC 98

Required Required with DVD-Video Required

All MPEG-2 decoder implementations—whether implemented as hardware, software, or a combination of both—must be capable of the following:

MPEG-2 Main Profile at Main Level (MP@ML) playback, with no dropped frames. Playback requirements include full-frame rate decode of MPEG-2 MP@ML input streams, up to and including the following frame sizes and rates:

720 × 480 at 60 fields per second720 × 480 at 24 frames per second

720 × 576 at 50 fields per second720 × 576 at 24 frames per second

Decoded frame rate is measured at the graphics frame buffer. The actual rate at which video is displayed (or rendered) is covered in the following requirement for smooth frame delivery.

Smooth frame delivery. Video frames must be displayed within one-half frame of the intended display time. This requirement is satisfied for implementations in which video frames are completely rendered into a DirectDraw surface and flipped using the DirectDraw Flip API or a hardware autoflip within one-half frame of the intended display time.

It is generally accepted in the video broadcast industry that any level of frame slippage or jitter will be noticeable to viewers and will be considered an annoyance compared to the smooth viewing experience provided by standard broadcast television, VCRs, and so on.

Rates for decoding and displaying data. This requires MPEG-2 data rates of up to 9.8 Mb/s for Consumer PC 98 and Office PC 98, and 15 Mb/s for Entertainment PC 98.

Synchronized audio and video. Audio and video must be synchronized to within one video frame.

Proper handling of field-based content. This requirement includes the dynamic field/frame switching capability.

No tearing. This requires proper video buffering, such as double buffering.

Correct display of multiple aspect ratio content. This requirement includes support for Pan Scan and letterbox-formatted content.

Closed captioning support. Line 21 data must be parsed out of the extension_and_user_data and made available for decoding for both DVD and digital broadcast satellite line 21 syntax.

Output of all remaining frames at the end of the data sequence. This requirement ensures output of all remaining frames when the decoder receives one of the following:

A sequence_end_code message (which differs from an Ipin::EndOfStream() function call)

A time discontinuity

Splicing MPEG. Decoders must properly interpret the Closed_Gop flag by dropping B frames before the first I frame after either a data discontinuity is received or the Broken_Link flag is set.

Notice the related video and MPEG-2 support requirements for graphics adapters, such as YUV (4:2:0 and 4:2:2) off-screen overlay surface and up/down bilinear interpolated scaling as defined in the “Hardware Acceleration for Video Playback” section in the “Graphics Adapters” chapter in Part 4 of this guide.

13. Retail adapters with hardware MPEG-2 decoders enable a standard video port connection to the graphics adapter

Required

Retail upgrade adapters sold independent of PC systems can use PCI for video transfer to the graphics adapter but must also enable a video port connection to the graphics adapter.

It is expected that an advanced video port specification will be standardized by the VESA Video Port committee within the PC 98 time frame. It is strongly recommended that MPEG-2 implementations on all PC systems and retail adapters comply with this standard as soon as possible after standardization. This will become a requirement in future versions of these design guidelines.

14. MPEG-2 decoder supports pull-down algorithm

Recommended

An MPEG-2 software or hardware decoder should be able to detect and behave accordingly when 3:2 pulldown (or any other algorithm) is being used to display 24-fps video. The kernel-mode video transport component in DirectDraw 5.0 requires this information from the decoder in order to know when a particular field-skipping algorithm is being used so it knows which fields to skip.

Notice that even if the subsystem supports 3:2 pulldown out of the decoder, the encoder should still be able to receive the 3:2 content.

For more information, see the DirectX 5.0 DDK; see also the article on http://www.microsoft/com/hwdev/devdes/.

Consumer PC 98	Office PC 98	Entertainment PC 98

Required	Required if no DVD-Video	Required