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Chapter 8. HAVi > Display Model

8.7. Display Model

There are some specialized requirements for running applications within a consumer electronic environment as opposed to the simpler situation that occurs when an applet is displayed within a PC. Most notably, the screen dimensions and aspect ratios are significantly different between PCs and devices. In the On-Screen Display (OSD) graphics model of today's set-top boxes, output video may be in a number of different configurations, including traditional 4:3 TV display, as well as 16:9 wide screen displays. The graphics resolution and aspect ratio are often locked to the video resolution and aspect ratio. If the video aspect pixel ratio changes, then the graphics pixel aspect ratio may also change. Thus, the key requirements are to determine the resolution and physical characteristics of the current display device, and detect modifications to the resolution and physical characteristics of the current display device.

8.7.1. Screen Reference Model

A model is provided that is designed to best fit the needs of consumer electronics devices. There are four layers of graphic display (see Figure 8.2): (a) the background plane, containing a static image or uniform pattern/color; (b) the video plane displaying the video-stream for the current virtual channel; (c) the application graphics plane displaying the GUI; and (d) the cursor plane displaying icons used for selection and status notification.


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