YCbCr
422
5 Tap
Polyphase
Scaler
YCbCr
422
2 tap bilinear
scaler
5 tap polyphase
scaler
mix
YCbCr
in
ev
YCbCr out
intp conf
[ conf * (1-conf) * YCbCr5 ]
conf
YCbCr2
YCbCr5
Edge
Detection
Yi
Internal Modules
195
SPRUHI7A – December 2012 – Revised June 2016
Copyright © 2012–2016, Texas Instruments Incorporated
High-Definition Video Processing Subsystem (HDVPSS)
1.2.11.2.3.1 Polyphase Scaler (in Vertical Scaler)
The vertical polyphase scaler is mainly implemented using a 32-phase 5-tap polyphase filter.
Figure 1-145. Mixed 2-tap and 5-tap vertical interpolation
NOTE:
In SC_M modules present in this device, edge detection and 2-tap bilinear filter modules are not
available.
1.2.11.2.3.1.1 Polyphase Filter Selection
The scaler (SC) uses 5-tap polyphase filtering for vertical up-scaling.
Figure 1-146. Vertical Polyphase Scaler Block Diagram (SC)
1.2.11.2.3.2 Running Average Filter
When a poly-phase filter is used, usually it has to have many taps in order to achieve acceptable quality
for very small downscaling ratio, which requires the use of many line buffers. In HDVPSS, we have a
weighted Running Average filter for downscaling when the scaling factor is small (for example, when the
scaling ratio is less than 0.5). This highly optimized design requires only one line buffer for luma and one
for chroma, which still achieving acceptable quality. The output of the running average filter is based on
weighted average of pixels in the current and previous rows in vertical direction. Initializations of
accumulators affect the weights.