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vp9: Adjust segment weight for cyclic refresh.

For screen-content: use the previous actual number of seg
blocks for the segment weight, used in the rate control
for setting frame-level Q.

Small overall increase in psnr on several screen-content clips.

Change-Id: Id414fb7f1b0ba578d464437d7f9c1783a0cad310

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

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

@@ -503,6 +503,14 @@

                    num8x8bl;

   if (weight_segment_target < 7 * weight_segment / 8)

     weight_segment = weight_segment_target;

+  // For screen-content: don't include target for the weight segment, since

+  // all for all flat areas the segment is reset, so its more accurate to

+  // just use the previous actual number of seg blocks for the weight.

+  if (cpi->oxcf.content == VP9E_CONTENT_SCREEN)

+    weight_segment =

+        (double)((cr->actual_num_seg1_blocks + cr->actual_num_seg2_blocks) >>

+                 1) /

+        num8x8bl;

   cr->weight_segment = weight_segment;

 }

-- 

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