Graphics Reference
In-Depth Information
Tabl e 4. 1
Relationship between intra prediction mode number and
associated names
Intra prediction mode number
Associated names
0
INTRA_PLANAR
1
INTRA_DC
2 :::34
INTRA_ANGULAR[i], i D 2 :::34
...
...
p
[-1][-1]
p
[0][-1]
p
[
N
-1][-1]
p
[2
N
-1][-1]
p
[-1][0]
p
[-1][
N
-1]
p
[-1][2
N
-1]
Fig. 4.1
An example of reference samples
p
[
x
][
1],
p
[
1][
y
] HEVC intra prediction uses for a
block of size
N
N
samples
of all the defined prediction modes for all the block sizes. Due to the very large
amount of different block size—prediction mode combinations all the prediction
modes have been designed in a way to allow easy algorithmic implementations
for arbitrary block sizes and prediction directions as discussed in the following
sections.
In order to improve the likelihood of finding good prediction candidates, HEVC
supports different filtering alternatives for pre-processing the reference samples
prior to applying those in the actual intra prediction process. Similarly, some of
the prediction modes include a post-processing step to refine the sample surface
continuity on the block boundaries as described in the following sections. Typical
characteristics of the different intra prediction modes are illustrated in Fig.
4.2
.
The figure represents the final predictions obtained with all the 35 HEVC intra
prediction modes when using reference samples shown in Fig.
4.1
as input. Effects
of the post-processing are visible for the DC prediction and angular modes 10
and 26 for which the prediction block boundaries include a component from the
neighboring sample values.
