Graphics Reference
In-Depth Information
Merge Index
Inter-picture
Prediction
Block Merging
Motion
Compensated
Prediction 0
Fractional
Sample
Interpolation
Weighted
Sample
Prediction
Final Motion
Compensated
Prediction
Advanced
Motion Vector
Prediction
Motion
Compensated
Prediction 1
Motion Data Coding
Motion Data
MV: ( x
0
, y
0
)
,( x
1
, y
1
)
RefIdx: t
0
, t
1
MVP Index 0
,1
MVD 0
,1
RefIdx
t
0
, t
1
Fig. 5.2
Inter-picture prediction in HEVC (
grey parts
represent the bi-prediction path)
estimation is not specified within video standards so different encoders can utilize
different complexity-quality tradeoffs in their implementations.
An overview block diagram of the HEVC inter-picture prediction is shown in
Fig.
5.2
. The motion data of a block is correlated with the neighboring blocks.
To exploit this correlation, motion data is not directly coded in the bitstream but
predictively coded based on neighboring motion data. In HEVC, two concepts are
used for that. The predictive coding of the motion vectors was improved in HEVC
by introducing a new tool called advanced motion vector prediction (AMVP) where
the best predictor for each motion block is signaled to the decoder. In addition, a new
technique called inter-prediction block merging derives all motion data of a block
from the neighboring blocks replacing the direct and skip modes in H.264/AVC [
26
].
Section
5.2
describes all aspects of motion data coding in HEVC including AMVP,
inter-prediction block merging and motion data storage reduction. The improved
fractional sample interpolation filter is explained in Sect.
5.3
. Additional weighting
of the MCP or, in case of bi-prediction, the weighting of the two MCPs is further
detailed in Sect.
5.4
. Finally, Sect.
5.5
summarizes and concludes this chapter.
5.2
Motion Data Coding
5.2.1
Advanced Motion Vector Prediction
As in previous video coding standards, the HEVC motion vectors are coded in terms
of horizontal (x) and vertical (y) components as a difference to a so called motion
vector predictor (MVP). The calculation of both motion vector difference (MVD)
components is shown in Eqs. (
5.1
)and(
5.2
).
MVD
x
D
x
MVP
x
(5.1)
MVD
y
D
y
MVP
y
(5.2)
