Graphics Reference
In-Depth Information
(compared with 8
8
9-bit in H.264/AVC) in order to reconstruct the coefficient
levels.
8.8.3.4
Context Initialization Tables
As already discussed in Sect.
8.7
, the memory requirements for storing the context
initialization tables in HEVC have been reduced to a large extent when compared to
those of H.264/AVC. Accounting for the reduction in number of contexts, number
of bits per InitValue and number of InitValue sets, HEVC has an 9
smaller context
initialization table than H.264/AVC.
8.9
Conclusions
Entropy coding was a highly active area of development throughout the HEVC
standardization process with proposals for both coding efficiency and throughput
improvement. The trade-off between the two requirements were carefully evaluated
in multiple Core Experiments and Ad Hoc Groups [
8
,
11
,
13
,
37
,
97
]. Beside coding-
efficiency improving technology, many techniques were incorporated to improve
throughput including reducing regular coded bins, grouping bypass bins together,
grouping bins that use the same contexts together, reducing context selection
dependencies, and reducing the total number of signaled bins. CABAC memory
requirements were also significantly reduced. The final design of CABAC in
HEVC shows that by accounting for implementation cost
and
coding efficiency
when designing entropy coding algorithms results in a design that can maximize
processing speed and minimize area cost, while delivering high coding efficiency in
the latest video coding standard.
References
1. Alshina E, Alshin A (2011) Multi-parameter probability up-date for CABAC, Joint Collabo-
rative Team on Video Coding (JCT-VC), Document JCTVC-F254, Torino, July 2011
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