Modified resize loop constraints.

Using a tighter resize constraint on undershoot seems to help
results (especially SSIM) as significant undershoot on a frame
seems to have more of a damaging impact than overshoot.

This patch has been tuned so that in local testing using the
derf set it is encode speed neutral for speed  setting 2.

Average quality result for speed 2 (psnr,ssim) were  as follows:-

 lowres  0.039,  0.453
 midres  0.249, 0.853
 hdres  0.159, 0.659
 NetFlix -0.241, 0.360

Change-Id: Ie8d3a0d7d6f7ea89d9965d1821be17f8bda85062

1 files changed, 4 insertions, 3 deletions

diff --git a/vp9/encoder/vp9_ratectrl.c b/vp9/encoder/vp9_ratectrl.c
index 5daad7458..223c01f0a 100644
--- a/vp9/encoder/vp9_ratectrl.c
+++ b/vp9/encoder/vp9_ratectrl.c
@@ -1233,10 +1233,11 @@ void vp9_rc_compute_frame_size_bounds(const VP9_COMP *cpi, int frame_target,
   } else {
     // For very small rate targets where the fractional adjustment
     // may be tiny make sure there is at least a minimum range.
-    const int tolerance = (cpi->sf.recode_tolerance * frame_target) / 100;
-    *frame_under_shoot_limit = VPXMAX(frame_target - tolerance - 200, 0);
+    const int tol_low = (cpi->sf.recode_tolerance_low * frame_target) / 100;
+    const int tol_high = (cpi->sf.recode_tolerance_high * frame_target) / 100;
+    *frame_under_shoot_limit = VPXMAX(frame_target - tol_low - 100, 0);
     *frame_over_shoot_limit =
-        VPXMIN(frame_target + tolerance + 200, cpi->rc.max_frame_bandwidth);
+        VPXMIN(frame_target + tol_high + 100, cpi->rc.max_frame_bandwidth);
   }
 }