Slightly more damped VBR adjustment.
Increase in the damping used in adjusting the active Q range. This does hurt rate accuracy a little in a few extreme cases especially if the clip is very short*, but helps metrics. * Note that the adjustment is applied at the GF/ARF group level based on what happened in the last group. Hence for very short clips where the length of a single group may be a significant % of the clip length there is still scope for some drift that cannot be accommodated. In practice most data points in our test sets are now much closer to target than was previously the case with default settings and in some cases are better even than they were with the command line undershoot and overshoot parameter was set very low (e.g. 2%). For example in bridge_close at high rates the old mechanism was unable to adapt enough to prevent extreme overshoot. Change-Id: I634f8f0e015b5ee64a9f0ccaa2bcfdbc1d360489