SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
This module down-samples the chroma components from 444-420 format; effectively reducing the chroma resolution to 50% in both the horizontal and vertical direction.
The downsampling is performed using a 3 Tap fitering [1 2 1] followed by decimation. The conversion logic generates chroma in co-sited/co-located format in both the horizontal and vertical direction.
Figure 6-113 shows the block diagram of the format conversion module. The Chorma output can be optionally downshifted from 12 bits to 8 bits using the LUT/SFT module. Only one copy of the Horizontal averaging filter is required since there is a decimation step following the filtering. Only even locations of both Cb/Cr are retained while the odd locations are decimated, however from design perspective the Hz Averager module works on Cb on even cycles and Cr on odd cycles.
Additionally another mode of operation is to support planar YUV422 mode. In this case the chroma is only downsampled in the horizontal direction and the vertical averaging/downsampling is disabled.
The mode is referred to pseudo 422 since actual 422 mode requires the data to be interleaved between the Y and the chroma channels. In this case the interleaving of Y & C is handled by LSE whereas the Flexible CC module will only generate Y & Cb/Cr (interleaved) planes separately.