Video and Image Processing Suite User Guide

ID 683416
Date 4/04/2022
Document Table of Contents

13. Chroma Resampler II IP Core

The Chroma Resampler II IP core resamples video data to and from common sampling formats.

The human eye is more sensitive to brightness than tone. Taking advantage of this characteristic, video transmitted in the Y’CbCr color space often subsamples the color components (Cb and Cr) to save on data bandwidth.

The Chroma Resampler II IP core allows you to change between 4:4:4 and 4:2:2 sampling rates where:

  • 4:4:4 specifies full resolution in planes 1, 2, and 3 (Y, Cb and Cr respectively)
  • 4:2:2 specifies full resolution in plane 1 and half width resolution in planes 2 and 3 (Y, Cb and Cr respectively)
Table 40.  Chroma Resampler II Sampling Support for Algorithms
Sampling (4:2:2 to 4:4:4 Algorithm
Nearest Neighbor Bilinear Filtered
Upsampling Yes Yes Yes
Downsampling Yes Yes Yes
Horizontal Resampling Yes No No
Vertical Resampling Yes No No

You can configure the Chroma Resampler II IP core to operate in one of two generalized modes: fixed mode and variable mode.

Table 41.  Chroma Resampler Modes
Fixed mode Variable mode
  • Both the input and output Avalon-ST Video interfaces are fixed to a set subsampling format, either 4:2:2 or 4:4:4.
  • Select either a fixed 4:4:4 to 4:2:2 downsampling operation, or a fixed 4:2:2 to 4:4:4 upsampling operation.
  • Enable fixed mode by setting the Variable 3 color interface parameter to NEITHER.
  • Does not support 4:2:0 format and does not provide the option for run-time control of the subsampling on either interface.
  • Configure either the input or output Avalon-ST video interface as a variable subsampling interface.
  • Has 3 color planes per pixel and may transmit data formatted as 4:4:4, 4:2:2 or 4:2:0 data, with the selected subsampling option set at run time through the Avalon-MM Slave control interface.
  • Enable variable mode by setting the Variable 3 color interface parameter to INPUT or OUTPUT.
    Note: If you leave the Variable 3 color interface parameter by the default selection, the IP core retains a fixed subsampling format of either 4:4:4 or 4:2:2.

The variable mode is mainly to be use with interface standards, such as HDMI 2.0, which allow color space and subsampling to vary at run time. Because most of the VIP IP cores support only a fixed subsampling (either 4:4:4 or 4:2:2), the Chroma Resampler II IP core is allows a variable-to-fixed conversion (Variable 3 color interface = INPUT) at the input to the processing pipeline, and a fixed-to-variable conversion (Variable 3 color interface = OUTPUT) at the output of the processing pipeline