Of itu-t sg16 wp3 and iso/iec jtc1/SC29/WG11

5Tool experiments (in SHVC)

5.1TE1: Upsampling filter

5.1.1TE1 summary and general discussion

JCTVC-L0021 TEA1: Summary Report Upsampling Filter [A. Segall, J. Chen, J. Dong, E. Alshina]

Test	Proponent	Avg.	BD-rate	x2	Avg.	BD-rate	x1.5	Enc.Time	Dec.Time
#		Y	U	V	Y	U	V
test 4.1 (L0083)	Samsung	−17.1	−12.4	−11.9	−26.9	−23.4	−22.3	111	126
test 4.2_(L0054) 6bit luma + K0378 chroma	InterDigital	−17.1	−12.4	−11.9	−26.9	−23.5	−22.4	107	125
test 4.3 (L0335)	Qualcomm	−17.1	−12.4	−11.9	−26.9	−23.4	−22.3	111	128
test 4.4 (L0083)	Samsung	−17.1	−12.4	−11.9	−26.9	−23.4	−22.3	111	124

Performance-wise, there was basically no difference.

Current “default” (4.1) as used in TE2+ was a design with 6 bit precision for luma and chroma (which is identical with the MC interpolation filter of HEVC in case of 2X, where chroma is using 5 bits)

For 2X scalability luma, there was no difference between the proposals. For chroma, 4.1-4.3 are identical, and 4.4 uses a different phase calculation for vertical upsampling (but still using one of the MC chroma interpolation filters)

For 1.5X scalability (which requires 1/3 phase position for luma and some more for vertical chroma which are not existing as MC interpolation filters), 4.1, 4.3 and 4.4 use the same luma filter, 4.2 uses a different one.

From the frequency response presented in the cross-check document JCTVC-L0088, the design of 4.1/4.3/4.4 seems to be closer to the MC interpolation filters (avoiding the “bumps” in the passband).

Decision: Adopt solution from 4.1/4.3/4.4 as default luma filter.

For 1.5X chroma where 1/3, 7/12 and 11/12 phase positions are additionally required, 4.3 uses 5 bit rounding, whereas 4.1/4.2/4.4 use 6 bit (and 4.4 uses different phase calc. with less accuracy).

5 bit rounding is more consistent with the MC interpolation filter design.

Decision: Adopt solution from 4.3 as default chroma upsampling filter.

Further study (AHG12) was planned on accuracy of chroma phase shift for possible simplification.

5.1.2TE1 primary contributions

JCTVC-L0054 TE1: Results of test 4.2 on fixed upsampling filter [J. Dong, Y. Ye (InterDigital)]
JCTVC-L0083 TEA1: Fixed up-sampling filter tests by Samsung (tests 4.1 and 4.4) [E.Alshina, A.Alshin, J.H.Park (Samsung)]
JCTVC-L0335 TE-A1: Results of test 4.3 on fixed up-sampling filter [J. Chen, R. Krishna, M. Karczewicz (Qualcomm)]

5.1.3TE1 cross checks

JCTVC-L0088 TEA1: Cross-check of fixed 6 and 7 bit-depth up-sampling filters performance (test 4.2) [E.Alshina, A.Alshin, J.H.Park (Samsung)]
JCTVC-L0089 TEA1: Cross-check of low bit-depth Chroma up-sampling filter (test 4.3) [E.Alshina, A.Alshin, J.H.Park (Samsung)]
JCTVC-L0396 TEA1: Cross check for Test 4.4 on chroma up-sampling filter (JCTVC-L0083) [M. Budagavi (TI)] [late]