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Terms

Output resolution

The resolution on the output device. the dimensions seen on the television 1080, 720, etc. These can be set in

Device Settings -> Video Display -> Output resolution

Video planeA plane dedicated to video-only output
Graphics planeA destination for rendering. Is often used to mean a frame-buffer
ScreenThe television
Device settings library (DS)RDK Component to interact with various hardware components on the STB.  HDMI, Component, and Composite video display ports are managed via the device settings library, as is the front panel brightness. 

Graphics

Application maintains a scene graph of Guide resources and draws these resources in a back-to-front ordering. The scene graph is rendered either via OpenGL ES or DirectFB. 

Planes and Coordinates Spaces

There are three coordinate spaces that the graphics developer needs to be aware of when working with graphics related code or when consulting with SOC developers on the proper implementation of various integration points. 

NOTE: All coordinate systems all have an origin in the upper left corner and increase down and right.

  1. Guide Plane - This is the coordinate space that the Guide Resources are using. These coordinates are already transformed into an absolute size and position. The size of this space is of particular importance to the UI engine. 
  2. Graphics Plane Space - This is typically the size of the graphics Framebuffer. Under special circumstances, the Graphics Plane may not the exactly the same size as the Framebuffer, but it is still backed by a Framebuffer. The terms Graphics Plane and Framebuffer are often used interchangeably. 
  3. Screen Space - This is the output resolution.

Scaling

Below is a hypothetical example of how the setup might look on a 4k display.

  1. The Guide resources are drawn to a coordinate space of 1280x720. 
  2. Application scales those resources using an OpenGL fragement shader onto a 1920x1080 Framebuffer.  Remember  "Framebuffer" and Graphics Plane are the same thing. 
  3. The underlying display driver further scales the Framebuffer to match the Screen Size. 


So in affect, the application drew a GUIDE in 1280x720 and it appeared perfectly scaled on a 3840x2160 TV. 

There are a couple assumptions made at this point:

  1. The Graphics Plane is ALWAYS scaled to match the Screen Size.
  2. The Graphics Plane and the Framebuffer are of equal size. Or at least the SOC presents the Framebuffer as the size of the Graphics Plane.
  3. The Guide Plane is 1280x720 as a matter of convenience. The application is capable of rendering a UI in any arbitrary Guide Plane size.

TrueSD

When the Output Resolution is considered to be standard definition, the Guide Plane is adjusted from the default 1280x720 to 640x480 with an exception for TrueSD mode.











Overview


Graphics Protocols


Graphics Drivers


Rendering


Browser Framework


QT


WPE


Westeros


Western


pxScene


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