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6th Meeting: Hobart, March 2017 2017-04-06 01:50
EE2-JVET related: Division-free bilateral filter
Authors: J. Ström Ericsson K. Andersson Ericsson P. Wennersten Ericsson Martin Pettersson Ericsson J. Enhorn Ericsson Rickard Sjöberg Ericsson
Abstract
During the Hobart meeting, it was requested to have a division-free implementation of the bilateral filter from JVET-F0034 test 2 demonstrated. It was also concluded that the smaller division-lookup-table (division-LUT) of about 1 kB was preferred. This contribution is a response to these requests. To keep the size of the division-LUT small, it is important to reduce the size of both the nominator and the denominator of the division. To reduce the nominator, the filter equation can be rephrased in a mathematically equivalent manner to work with differences instead of absolute values. To reduce the denominator, bilateral filtering is turned off for inter blocks of size 16×16 and larger, which avoids a large center weight coefficient. With these changes, this contribution asserts that it is possible to make a division-free implementation where the division-LUT has a size of 576 bytes. The result by using the division-LUT is identical to the result from using divisions. The reported BD rate numbers are 0.4% / 0.5% / 0.5% / 0.5% for AI / RA / LD / LDP.
Meeting Notes
JVET-F0096 EE2-JVET related: Division-free bilateral filter [J. Ström, K. Andersson, P. Wennersten, M. Pettersson, J. Enhorn, R. Sjöberg (Ericsson)] [late]

During the Hobart meeting, it was requested to have a division-free implementation of the bilateral filter from JVET-F0034 test 2 demonstrated. It was also concluded that a smaller division-lookup-table (division-LUT) of about 1 kB was preferred. This contribution was a response to these requests. To keep the size of the division-LUT small, it is important to reduce the size of both the numerator and the denominator of the division. To reduce the numerator, the filter equation can be recast in a mathematically equivalent manner to work with differences instead of absolute values. To reduce the denominator, bilateral filtering is turned off for inter blocks of size 16×16 and larger, which avoids a large center weight coefficient. With these changes, this contribution asserts that it is possible to make a division-free implementation where the division-LUT has a size of 576 bytes. The result by using the division-LUT is reportedly identical to the result from using divisions. The reported BD rate numbers are −0.4% / −0.5% / −0.5% / −0.5% for AI / RA / LD / LDP, respectively.

Some concern was raised about complexity in particular for the AI case a) in terms of encoder runtime (though less than other tools such as PDPC); b) in terms of decoder side where the tool is in the innermost prediction loop and may require switching at each sample position. However, the expert who raised this concern did not strongly object against adoption to the experimental JEM framework, though his opinion was that this would not be a good tradeoff yet when put into a final standard.

Other experts (in particular, cross-checkers) expressed the opinion that with the new modifications, the tool provides a reasonable tradeoff between complexity and compression, and its inclusion in JEM was supported.

Decision: Adopt JVET-F0096.

JVET-F0096 EE2-JVET related: Division-free bilateral filter [J. Ström, K. Andersson, P. Wennersten, M. Pettersson, J. Enhorn, R. Sjöberg (Ericsson)]

Changes in 360lib

References:
JVET-F0034
Cited:
JVET-F0099 X JVET-F0100 X JVET-F0101 X JVET-F1001 JVET-G0076 JVET-G1001 JVET-K0231 JVET-K0274 JVET-L0172
ARCHIVE v2 :
division_free_noInter16x16.patch JEM5.0.1_vs_EE2_Test2_noInter16x16.xlsm JVET-F0096.docx JVET-F0096_Division_free_bilateral_filter.pptx ~$ET-F0096.docx ~$JEM5.0.1_vs_EE2_Test2_noInter16x16.xlsm
Decisions
adopted
Adopt JVET-F0096
Changes in 360lib
Citation