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and delay. Note that it is important to include both quality measures; relying solely
on objective quality evaluations could, in cases, underestimate the amount of bit
rate reduction and hence affect our analysis of compression efficiency. Subjective
quality evaluations on the other hand, although difficult to conduct, correlate directly
with perceptual experience of the viewers. This chapter is organized as follows.
Section
9.1
provides the background information and forms the basis for the sections
that will follow. In Sect.
9.2
encoder settings and testing conditions are described
by considering various encoder configurations according to complexity and delay
requirements; moreover, a list of test sequences used, test cases and the description
of non-normative R-D optimization tools that contribute significantly to coding
efficiency improvement are also covered in this section. In Sect.
9.3
, objective
quality evaluations of HEVC and AVC reference implementations are investigated.
In Sect.
9.4
, we present the results of HEVC subjective quality testing and visual
assessments of HEVC and AVC. Section
9.5
describes an informal subjective video
quality comparison of production-quality HEVC and AVC encoders in the context
of 4K streaming applications. Conclusions appear in Sect.
9.6
.
9.2
Encoder Setting
To conduct HEVC and AVC performance evaluations, a well-defined encoder
setting and testing environment need to be established. In this section, we will
describe, the HEVC and AVC reference encoder software (SW) used in our
investigations. In addition, we will also describe various encoder configurations and
prediction structures that are appropriate for different application requirements in
terms of coding efficiency, complexity and delay.
9.2.1
Encoder Software
In the standardization of HEVC, the reference software, which is called HM (HEVC
Test Model, reference software) [
15
] has been developed as a common SW platform
for further improvement and study. Using SVN servers, the HM reference software
is maintained at two sites [
16
]: HHI (Heinrich Hertz Institute) maintains the main
SVN server and BBC (British Broadcasting Corporation) maintains the mirroring
repository site.
The reference software for AVC, which is called JM (Joint Test Model), has
been developed, as a common test platform, for AVC performance evaluations. The
JM reference software is maintained at SVN server [
6
]. In this chapter, in order to
compare the coding performance of HEVC with AVC, HM12.1 and JM18.5 SW are
used for HEVC and AVC encoders, respectively.
