Game Development Reference
In-Depth Information
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Fig. 5.2
Transform a residual block in diagonal down-left intra mode with directional DCT (Zeng
and Fu
2008
;Zhaoetal.
2012
)
step, directional
DCT
performs seven 1-D DCTs along each of the diagonal down-
left directed lines and a
DC
correction process is implemented after the first 1-D
DCT to handle the so-called mean weighting defect (Zeng and Fu
2008
). In the
second step, the DC components of each 1-D transform coefficients are aligned and
four 1-D DCT is performed along the diagonal down-right directed lines. Finally, in
the third step, the DC components are aligned again and the transform coefficients
are quantized and scanned to a 1-D vector, after that, the 1-D vector is delivered to
entropy encoder.
The
MDDT
method proposes to use
KLT
for intrapredicted residues. For intrapre-
diction, since the reference samples always come from the left and right block
boundary, and there are typically various prediction directions, the intrapredicted
residues present certain distribution statistics for a specific intraprediction. As shown
Fig. 5.3
Normalized distributions of residue magnitudes in different intraprediction modes (Zhao
et al.
2012
)
a
vertical,
b
horizontal,
c
dc,
d
diagonal down-left,
e
diagonal down-right,
f
top-right,
g
bottom-down,
h
top-left,
i
bottom-up
