Game Development Reference
In-Depth Information
3.2.4 Transform
Two level transform coding is utilized to further compress the predicted residual. For
CU with symmetric prediction unit partition, the TU size can be 2N
×
2N or N
×
N
signaled by a transform split flag. Thus, the maximum transform size is 64
×
64, and
the minimum is 4
32, an Integer Transform (IT)
that closely approximates the performance of the discrete cosine transform (DCT)
is used; while for 64
×
4. For TU size from 4
×
4to32
×
64 transform, a logical transform (LOT) (Lee et al.
2012
)is
applied to the residual. A 5-3 tap integer wavelet transform is first performed on a
64
×
×
64 block discarding the LH, HL, and HH-bands, and then a normal 32
×
32 IT
is applied to the LL-band. For a CU that has an asymmetric PU partition, 2N
2N
IT is used in the first level and a non-square transform (Li et al.
2013
)isusedinthe
second level, as shown in Fig.
3.6
.
×
3.2.5 Entropy Coding
After transform and quantization, a two level coding scheme is applied to the trans-
form coefficient blocks (Wang et al.
2012
). A coefficient block is partitioned into
Fig. 3.6
Two level transform coding
