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kLevelsFromDelta[sharpness][delta] is an inverse look-up table that tells the minimum filtering strength needed to trigger the filtering of a step with amplitude 'delta'. We use this table in various situations: a) when computing the initial (/global) filtering strength for each segment. We look at the quantization step and deduce the proper filtering strength needed to result this quantization noise (talking the -f option into account). b) during intra16 calculation, when a block ends up very empty (only DC coeffs are non-zero, all ACs have vanished). We'll rely on the in-loop filtering to restore the smoothness (if the source was gradient-like smooth. That's why we look at the distortion too before triggering the filtering). Step b) goes _in addition_ to a), potentially raising the filtering strength if blockiness is likely. Change-Id: Icaeca93ef21da195b079e6587a44d9edfc8e9efa