vp9: Adjust threshold for scene-change detection.

For 1 pass vbr.

Change-Id: I10b7eefc36d65c30844d205e139515bec7fed6af

vp9/encoder/vp9_ratectrl.c

diff --git a/vp9/encoder/vp9_ratectrl.c b/vp9/encoder/vp9_ratectrl.c
index aa508de..e06d56b 100644
--- a/vp9/encoder/vp9_ratectrl.c
+++ b/vp9/encoder/vp9_ratectrl.c
@@ -2074,8 +2074,8 @@
     // for cases where there is small change from content that is completely
     // static.
     if (cpi->oxcf.rc_mode == VPX_VBR) {
-      min_thresh = 40000;
-      thresh = 2.0f;
+      min_thresh = 60000;
+      thresh = 2.1f;
     }
     if (avg_sad >
         VPXMAX(min_thresh, (unsigned int)(rc->avg_source_sad  * thresh)) &&