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11th Meeting: Ljubljana, July 2018 2018-07-10 10:22
CE9.5.2: BIO with simplified gradient calculation, adaptive BIO granularity, and applying BIO to chroma components
Authors: C.-Y. Chen MediaTek C.-Y. Lai MediaTek Y.-W. Huang MediaTek Shawmin Lei MediaTek
Abstract
In this contribution, three aspects of bi-prediction optical flow (BIO) modifications as planned in Core Experiment 9.5.2 (CE9.5.2) are proposed. The first aspect is simplified gradient calculation. Compared to JEM-7.0 BIO, gradients of fewer samples are used for one BIO block in this proposal. Beside, gradients are calculated directly on interpolated samples to be used for inter prediction, i.e., samples of motion compensation (MC) results, using a phase independent gradient filter, i.e., one gradient filter for all integer and fractional motion vectors (MVs), while in JEM-7.0 one additional set of interpolation filters different from MC interpolation filters and one additional set of phase dependent gradient filters are used. In addition, the number of reference picture samples accessed during MC for BIO is kept the same as that for non-BIO by applying padding, so the proposed BIO does not increase any MC memory bandwidth. Finally, the division operation is replaced with shift operations only. The second aspect is adaptive BIO granularity (i.e., adaptive BIO block size) according to picture size. BIO derives displacement vectors at BIO block level (i.e., one displacement vector for all samples in one BIO block). The BIO block size is reduced from 4x4 to 2x2 for small pictures, which only impacts Class D sequences more and has zero or negligible effects for rest sequences in the test set. The third aspect is applying BIO to chroma components. Luma displacement vectors are reused and scaled for chroma components. The results are summarized as follows.
Meeting Notes
JVET-K0255 CE9.5.2: BIO with simplified gradient calculation, adaptive BIO granularity, and applying BIO to chroma components [C.-Y. Chen, C.-Y. Lai, Y.-W. Huang, S.-M. Lei (MediaTek)]
References:
JVET-J0018 JVET-J0029 JVET-J1010
Cited:
JVET-K0485 JVET-L0099
PATENTS:
EP3790607B1 0.34 2023-12-27 CA2935378C 0.32 2023-04-18 US9211315B2 0.30 2015-12-15 US11793841B2 0.28 2023-10-24 CN114981779B 0.26 2026-01-13 US20210192287A1 0.24 2021-06-24 KR102908166B1 0.22 2026-01-07 US11476959B2 0.20 2022-10-18
ARCHIVE v2 :
JVET-K0255-v1.docx JVET-K0255_Presentation.pdf JVET-K0255_Table1.xlsm JVET-K0255_Table2.xlsm JVET-K0255_Table3.xlsm JVET-K0255_Table4.xlsm
Decisions
JVET-K0255 CE9.5.2: BIO with simplified gradient calculation, adaptive BIO granularity, and applying BIO to chroma components [C.-Y. Chen, C.-Y. Lai, Y.-W. Huang, S.-M. Lei (MediaTek)]
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