Add variance restriction to AQ2.
Add an additional restriction to bit/complexity based segmentation based on spatial variance. Only lower Q when both the number of bits spent in the initial encoding pass and the spatial complexity are below a threshold. This will prevent the low Q segments being used just because there is a surfeit of bits. Small metrics gains especially opsnr. derf ~0.2% std-hd ~0.3% Change-Id: I6a8496d466d673f9b0e2b2ca6304ea7b6d8e1cce