Page 136 - ITU Journal, ICT Discoveries, Volume 3, No. 1, June 2020 Special issue: The future of video and immersive media

ITU Journal: ICT Discoveries, Vol. 3(1), June 2020

Table 2 – Coding performance comparison of LCEVC
(LTM 4.0) over AVC/HEVC anchor (JM/HM)
8
Video data set PSNR VMAF MOS 6
(base & anchor codec) MOS 4
Avg. A (H.264/AVC) −36.46% −43.44% −44.98% 2
Avg. A (H.265/HEVC) −8.77% −24.34% −43.05%
Avg. B (H.264/AVC) 12.40% −20.68% −31.98% 0
0 10,000 20,000 30,000
Subjective tests using formal Mean Opinion Scores Bit rate (kbps)
(MOS) according to ITU-R BT.2095 [11] were Fig. 4 – RD-curves for sequence A1 using
performed by the GBTech Laboratories under the H.264/AVC as base and anchor codec
supervision of Vittorio Baroncini, Chair of MPEG
Test Group. The results highlight greater MOS
benefits than what has been suggested by objective ParkRunning3
metrics. The results per sequence are also shown in 35
Table 2 and were calculated using the Bjøntegaard 33
metric. The better correlation of VMAF with PSNR (dB) 31
subjective MOS results is likely due to VMAF having 29
been designed to assess the visual quality of
encodes at different resolutions with the “convex 27 0 10,000 20,000 30,000
hull” methodology [12], and thus in the presence of Bit rate (kbps)
spatial scaling. PSNR is known to be less reliable at
approximating subjective assessments when 90
comparing different codecs, especially in the
presence of scaling [13][14]. 80
Figures 4 to 11 show the rate-distortion (RD) curves VMAF 70
for each sequence in the data set A using the 60
reference implementation of LCEVC, as well as 50
H.264/AVC and H.265/HEVC as the base and anchor 0 10,000 20,000 30,000
Bit rate (kbps)
codecs.
LTM 4 (JM/HM) JM/HM 6

4
Campfire MOS
38 2

PSNR (dB) 36 0 0 10,000 20,000 30,000

34
Bit rate (kbps)
32 Fig. 5 – RD-curves for sequence A2 using
0 10,000 20,000 30,000
Bit rate (kbps) H.264/AVC as base and anchor codec

100 FoodMarket4
40
90 38
VMAF 80 PSNR (dB) 36
34
70 32
30
0 10,000 20,000 30,000 28
Bit rate (kbps) 0 5,000 10,000 15,000
Bit rate (kbps)

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