Fix for loop filter selection procedure

Fixed best error reported by loop filter selection, this value is used
during loop restoration to pick best mode. Baseline remains unchanged,
change in BDRate for loop restoration experiment:
-0.628 -> -0.625 for lowres,
-1.262 -> -1.283 for highres.

Change-Id: I69ef1608bc232b250ac46f59e31fdbed1a999dcd

vp10/encoder/picklpf.c

@@ -120,11 +120,11 @@ int vp10_search_filter_level(const YV12_BUFFER_CONFIG *sd, VP10_COMP *cpi,
       }
       // If value is close to the best so far then bias towards a lower loop
       // filter value.
-      if ((ss_err[filt_low] - bias) < best_err) {
+      if (ss_err[filt_low] < (best_err + bias)) {
         // Was it actually better than the previous best?
-        if (ss_err[filt_low] < best_err)
+        if (ss_err[filt_low] < best_err) {
           best_err = ss_err[filt_low];
-
+        }
         filt_best = filt_low;
       }
     }
@@ -134,7 +134,8 @@ int vp10_search_filter_level(const YV12_BUFFER_CONFIG *sd, VP10_COMP *cpi,
       if (ss_err[filt_high] < 0) {
         ss_err[filt_high] = try_filter_frame(sd, cpi, filt_high, partial_frame);
       }
-      // Was it better than the previous best?
+      // If value is significantly better than previous best, bias added against
+      // raising filter value
       if (ss_err[filt_high] < (best_err - bias)) {
         best_err = ss_err[filt_high];
         filt_best = filt_high;
@@ -150,6 +151,10 @@ int vp10_search_filter_level(const YV12_BUFFER_CONFIG *sd, VP10_COMP *cpi,
       filt_mid = filt_best;
     }
   }
+
+  // Update best error
+  best_err = ss_err[filt_best];
+
   if (best_cost_ret)
     *best_cost_ret = RDCOST_DBL(x->rdmult, x->rddiv, 0, best_err);
   return filt_best;

vp10/encoder/pickrst.c

@@ -146,17 +146,16 @@ static int search_filter_bilateral_level(const YV12_BUFFER_CONFIG *sd,
     if (filt_direction <= 0 && filt_low != filt_mid) {
       // Get Low filter error score
       if (ss_err[filt_low] < 0) {
-        bilateral_lev = search_bilateral_level(sd, cpi, filt_low,
-                                          partial_frame, &ss_err[filt_low]);
+        bilateral_lev = search_bilateral_level(
+            sd, cpi, filt_low, partial_frame, &ss_err[filt_low]);
       }
       // If value is close to the best so far then bias towards a lower loop
       // filter value.
-      if ((ss_err[filt_low] - bias) < best_err) {
+      if (ss_err[filt_low] < (best_err + bias)) {
         // Was it actually better than the previous best?
         if (ss_err[filt_low] < best_err) {
           best_err = ss_err[filt_low];
         }
-
         filt_best = filt_low;
         restoration_best = bilateral_lev;
       }
@@ -168,7 +167,8 @@ static int search_filter_bilateral_level(const YV12_BUFFER_CONFIG *sd,
         bilateral_lev = search_bilateral_level(
             sd, cpi, filt_high, partial_frame, &ss_err[filt_high]);
       }
-      // Was it better than the previous best?
+      // If value is significantly better than previous best, bias added against
+      // raising filter value
       if (ss_err[filt_high] < (best_err - bias)) {
         best_err = ss_err[filt_high];
         filt_best = filt_high;
@@ -185,6 +185,10 @@ static int search_filter_bilateral_level(const YV12_BUFFER_CONFIG *sd,
       filt_mid = filt_best;
     }
   }
+
+  // Update best error
+  best_err = ss_err[filt_best];
+
   *restoration_level = restoration_best;
   if (best_cost_ret) *best_cost_ret = best_err;
   return filt_best;