High Definition Video Playback

Note: Microsoft received considerable feedback on this section and are evaluating updates for the RC milestone. However, it has not changed significantly for the Beta. Changes under consideration include adding a few clips to exercise higher-end performance, and lowering the scoring associated with playing clips 1, 2, 4 to level 3 or 4.

HD playback is a very important scenario for Windows 7. WinSAT (Windows System Assessment Tool) includes support for detailed analysis of a system’s ability to play back HD video in WMV, MPEG-2 and H.264 formats. This ability is reflected in the graphics score (not the gaming graphics score).

There are many ways to judge and measure video playback capability. WinSAT has been enhanced to measure and assess the system’s ability to reliability and accurately deliver video frames to the display and to the system resources needed to deliver the video.

For playback, the two key metrics are timeliness and dropped frames. Timeliness means delivering frames to the display isochronously –inside a specified window of time. Resource utilization metrics include GPU time, CPU time, graphics memory and system memory.

In addition, HD video is not a single format; it encompasses several codecs, sizes, bit rates and other characteristics. For Windows 7, Microsoft worked with the video playback team and agreed upon 6 video clips with the following formats :

In the context of WinSAT and WinEI, Microsoft is defining the term video playback accuracy to be a measure of dropped or late frames. By measuring a small set of canonical video clips, a system’s overall ability to accurately playback various video formats can be reported. For this scenario, the WinEI scores will map relatively directly to user experience :

• < 5.0 means the system does not support HD video playback.
  - The graphics score for systems that fail to playback all the HD video clips will be limited to a score of 4.9.
   
• 5.0+ means the system supports basic HD video playback. 
  - To achieve 5.0, the system must be able to successfully playback all of the basic clips (1, 2 and 4); and the existing (Windows Vista) standard definition WMV clip.
   
• 6.0+ means the system is a robust HD video playback platform.
  - For this level, the system must be able to play all the HD video clips successfully.

The video clips are short (five seconds) and thus do not include many key frames. Therefore, the video playback assessment will have zero tolerance for dropped or late frames.

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