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18.1. About the Scaler
The scaler can resize an incoming video field to produce an output field of any size, restricted only defined minimum and maximum widths and heights. You set the desired output field width and height at runtime via the register map (if the Avalon memory-mapped control agent interface is enabled), or via fixed parameters (if the Avalon memory-mapped control agent interface is not enabled). Full variants define the input field width and height by the image info packets received at the input interface. Lite variants define the input field width and height via the register map. With defined input and output widths and heights, the scaler applies the correct horizontal and vertical scaling ratios (which may be different).
The following bounds apply to the input and output field widths.
- Input field width must be less than or equal to the value set in the maximum input field width parameter.
- Output field width must be less than or equal to the value set in the maximum output field width parameter
- Output field width must be greater than or equal to the value set in the number of pixels in parallel parameter
You may also choose to turn off scaling in the horizontal or vertical directions if either is not required. In this case, the output width or height will be unaltered, regardless of the settings in the register map. Also, the scaler only supports scaling for video with 4:4:4 chroma siting. Full variants assert the error flag for any of these restrictions.
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