Graphics Reference
In-Depth Information
Tabl e 9. 11
Video sequences used for the subjective quality comparison in
order of presentation (top to bottom)
Frame
count
Frame
rate (fps)
Bit
depth
Resolution
Sequence name
3,840
2,160
IntoTrees
400
50
8
3,840
2,160
OldTownCross
400
50
8
3,840
2,160
ParkJoy
400
50
8
3,840
2,160
DucksTakeOff
400
50
8
9.5.1.1
Encoder Settings
The encoders were configured for high coding efficiency operation. More specifi-
cally, the HEVC encoder was configured for Main profile and to use a prediction
structure similar to that described in Sect.
9.2.3.2
with the period of the intra
pictures set to 48 frames. The AVC encoder was configured to use default parameter
values except for those parameters that required an explicit setting (e.g., the
keyint parameter, used to specify the intra frame period, was set to 48). Several
AVC encodings were performed for each video sequence, each with a different
quantization parameter (QP) value. In each case, the encoding that yielded an
average bit rate closest to 2.5 times that of the corresponding HEVC encoding was
selected (i.e., the bit rate of the HEVC encoded sequence was approximately 60 %
lower than that of the AVC encoded sequence).
9.5.1.2
Subjective Evaluation Conditions
Twenty-seven (27) volunteer viewing subjects were used for the subjective experi-
ments. Fifteen (15) of the viewers had little or no previous experience in evaluating
video sequences. The viewing was conducted in a somewhat-darkened room using
a XBR55X900A 55
00
UHD Sony Bravia LED monitor. Additional key elements of
the subjective evaluation and video presentation methodology are listed below:
1. Untrained viewers participated one at a time with each viewer seated in a chair
that was positioned approximately 1.5 meters from the monitor and centered.
2. For each of the four test sequences listed in Table
9.11
, the HEVC and AVC
encoded video sequences were cropped in the horizontal dimension and spliced
together side-by-side.
2
The relative position of the compared encodings was
randomized and the experiments were executed in a double-blind manner.
3. The sequences were displayed at their native spatial resolutions; however, the
display rate was set to 30 frames per second (fps) (i.e., the sequences were
displayed at 60 % of their native 50 fps frame rate).
2
The horizontal cropping removed one half of the pixels so as to enable both the HEVC and AVC
encoded sequences to be displayed side-by-side on the 3840 pixel-wide 4K monitor.
