This is so we may update level at any time (e.g., to be used
for setting thresholds in variance-based partition).
Change-Id: I32caad2271b8e03017a531f9ea456a6dbb9d49c7
Source noise level estimate is also useful for
setting variance encoder parameters (variance thresholds,
qp-delta, mode selection, etc), so allow it to be used also
if denoising is not on.
Change-Id: I4fe23d47607b4e17a35287057f489c29114beed1
