Low-complexity mode decision for MVC Liquan Shen, Zhi Liu, Ping
An, Ran Ma and Zhaoyang Zhang CSVT 2010 1
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Outline Introduction Early SKIP mode decision Adaptively early
termination Fast mode size decision Selectively intra coding in
inter frame Overall algorithm Experiment results 2
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Introduction Two frames of the same time instant from different
views correspond to the same content with similar video
characteristic.(prediction mode, RDcost, motion vector) SKIP mode
and RDcost correlation among inter-views are not fully studied
Early SKIP mode decision Adaptively early termination Fast mode
size decision Selectively intra coding in inter frame 3 View 0 View
1View 2
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Early SKIP mode decision Observation Many MBs finally end up
with being decided as SKIP mode because they belong to background
or motionless object. Previous method If SKIP mode has an RDcost
less than a predefined threshold, the variable size ME and DE
process are skipped. How to find a reasonable threshold is a
serious problem This approach method Coding mode among inter-views
are similar. Utilizing DE to find corresponding MBs among different
views, coding information can be effectively shared and reused from
the coded view channel. 4
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Early SKIP mode decision Idea When the corresponding MB in the
frame of the same time instant from the neighbor view is with SKIP
mode, the MB tends to have SKIP mode as well. 5 GDV
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Early SKIP mode decision In this work, coding information is
derived from the forward inter-view reference frame. GDV is not
exactly disparity between the current MB and the corresponding one,
the mode of the corresponding MB and its eight neighboring MBs are
used to estimate mode characteristics of a MB. A MB after
quantization with all zero coefficient (All-zero block) is
preferred to be coded with SKIP mode. Once the SAD between a block
and its matching block is smaller than a threshold, the current MB
is early decided as SKIP mode. 6
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Early SKIP mode decision I the MBs whose corresponding MB and
its eight neighboring MBs in the previously coded view are all
coded with SKIP mode. II remaining MBs in the current frame 7 36%
13.6%
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Adaptive early termination Idea The majority of best prediction
modes after mode decision are with large sizes such as 16x16, 16x8,
8x16. Threshold-based early termination N: 9 When the RDcost of
current MB is smaller than the threshold early termination 8
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Adaptive early termination 9 < 0.2% 96%
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Fast inter mode size decision 10 [9] L. Shen, T. Yan, Z. Liu;
Z. Zhang; P. An; Lei Yang, Fast mode decision for multiview video
coding, in Proc. IEEE ICIP, Nov. 2009, pp. 2593-2596.
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Fast inter mode size decision 11
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Fast inter mode size decision Fast sub-mode decision Based on
the information from the corresponding 8x8 block and its eight
neighboring blocks in the previously coded view. One of them with
4x4 complex sub-mode perform all sub-mode One of them with 8x4 or
4x8 normal sub-mode perform 8x8, 8x4, 4x8 Otherwise perform only
8x8 12
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Selective intra prediction in inter frame The intra mode are
enabled when a MB satisfies one of the following two conditions:
One MB among the corresponding MB and its eight neighboring MBs in
the previously coded view is coded with intra modes. RDcost value
of inter prediction for current MB is larger than the maximum of
RDcost from these nine corresponding MBs. 13 Enableskip
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Overall algorithm Step1: start mode decision for a MB Step2:
locate the corresponding MB and its eight neighboring MBs from the
previously coded view by GDV Step3: derive the prediction mode and
RDcost of these MBs 14
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Overall algorithm Step4: if the corresponding MB and its eight
neighboring MBs are all coded with SKIP mode or the SAD value of
SKIP mode for the current MB satisfied the AZB condition, perform
early SKIP mode decision Step5: compute Thr for RDcost based on
Eq.1 and MC based on Eq.2 Step6: test inter16x16 and get the
minimal RDcost. If RDcost is smaller than Thr, go to Step12; else
if the current MB is simple mode, go to Step10; else go to Step8
(Early termination&Fast inter mode size decision) 15
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Overall algorithm Step7: test inter16x8 and get the minimal
RDcost. If the minimal RDcost is smaller than Thr, goto Step12;
else if the current MB is normal mode, go to Step10; else go to
Step9(Early termination&Fast inter mode size decision) Step8:
test inter8x16 and get the minimal RDcost. If the minimal RDcost is
smaller than Thr, goto Step12; else if the current MB is normal
mode, go to Step10; else go to Step9(Early termination&Fast
inter mode size decision) Step9: for each 8x8, when one of the
corresponding block and its eight neighboring blocks With 4x4, test
all sub-mode With 4x8 or 8x4, test inter8x8, 8x4, 4x8 Otherwise,
test inter8x8 if RDcost is smaller than Thr, go to Step12; else go
to Step10 (Early termination) 16
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Overall algorithm Step10: check the conditions to skip intra
prediciton If RDcost of inter prediction for current MB is smaller
than the maximum of RDcosts from the corresponding MB and its eight
neighboring MBs and these MBs are all coded with inter modes, skip
intra prediction and go to Step 12; else go to Step 11. Step11:
perform intra prediction Step12: determine the best prediction
mode. Go to Step1 and proceed with next MB 17
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Experiment results JMVM 6.0 GOP 16 Search range 64 QP varies
from 24 to 36 Enable motion skip mode Compare to JMVM & the
fast inter frame prediction algorithm for MVC (FIFPMVC) [7] &
the selective DE and variable size ME algorithm (SDEME) [8] &
fast mode decision algorithm (FMD) [9] Three views of test
sequences are chosen for simulation. The second view is used for
the implementation of the proposed algorithm [7] X. M. Li, D. B.
Zhao, X. Y. Ji, Q. Wang, W. Gao, A fast inter frame prediction
algorithm for multi-view video coding, in Proc. IEEE ICIP, Sep.
2007, pp. 417-420,. [8] L. Shen, Z. Liu, S. Liu, Z. Zhang, and P.
An, Selective disparity estimation and variable size motion
estimation based on motion homogeneity for multi-view coding, IEEE
Trans. Broadcast., vol. 55, no. 4, pp. 761-766, Dec. 2009. [9] L.
Shen, T. Yan, Z. Liu; Z. Zhang; P. An; Lei Yang, Fast mode decision
for multiview video coding, in Proc. IEEE ICIP, Nov. 2009, pp.
2593-2596. 18