shithub: libvpx

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vp9: Adjust the weight factor for segment rate cost for aq-mode=3.

Use the segment weight factor based on the target (cr->percent_refresh)
if it less than the current estimate (avergae of past usage and target).
Small improvement at low bitrates.

Change-Id: Iba8fd909e203f94458901366d3a991f7ea854d49

--- a/vp9/encoder/vp9_aq_cyclicrefresh.c

+++ b/vp9/encoder/vp9_aq_cyclicrefresh.c

@@ -128,16 +128,20 @@

   CYCLIC_REFRESH *const cr = cpi->cyclic_refresh;

   int bits_per_mb;

   int num8x8bl = cm->MBs << 2;

+  // Compute delta-q corresponding to qindex i.

+  int deltaq = compute_deltaq(cpi, i, cr->rate_ratio_qdelta);

   // Weight for segment prior to encoding: take the average of the target

   // number for the frame to be encoded and the actual from the previous frame.

+  // Use the target if its less.

   int target_refresh = cr->percent_refresh * cm->mi_rows * cm->mi_cols / 100;

+  double weight_segment_target = (double)(target_refresh) / num8x8bl;

   double weight_segment =

       (double)((target_refresh + cr->actual_num_seg1_blocks +

                 cr->actual_num_seg2_blocks) >>

                1) /

       num8x8bl;

-  // Compute delta-q corresponding to qindex i.

-  int deltaq = compute_deltaq(cpi, i, cr->rate_ratio_qdelta);

+  if (weight_segment_target < 7 * weight_segment / 8)

+    weight_segment = weight_segment_target;

   // Take segment weighted average for bits per mb.

   bits_per_mb = (int)((1.0 - weight_segment) *

                           vp9_rc_bits_per_mb(cm->frame_type, i,