Adapt ARNR filter length and strength.

Adjust the filter length and strength for each
ARF group based on a measure of difficulty (the boost)
and the active q range.

Remove lower limit on RDMULT value.

Average gains on the different sets in range 0.4%-0.9%.
However the ARNR changes give a very big boost on a
few clips.

Eg. Soccer ~5%, in derf set and Cyclist ~ 10% in the std-hd set

Change-Id: I2078d78798e27ad2bcc2b32d703ea37b67412ec4

vp9/encoder/vp9_firstpass.c

@@ -1428,11 +1428,14 @@ static int calc_arf_boost(
   return arf_boost;
 }
 
-static void configure_arnr_filter(VP9_COMP *cpi, FIRSTPASS_STATS *this_frame) {
+static void configure_arnr_filter(VP9_COMP *cpi,
+                                  FIRSTPASS_STATS *this_frame,
+                                  int group_boost) {
   int half_gf_int;
   int frames_after_arf;
   int frames_bwd = cpi->oxcf.arnr_max_frames - 1;
   int frames_fwd = cpi->oxcf.arnr_max_frames - 1;
+  int q;
 
   // Define the arnr filter width for this group of frames:
   // We only filter frames that lie within a distance of half
@@ -1477,6 +1480,25 @@ static void configure_arnr_filter(VP9_COMP *cpi, FIRSTPASS_STATS *this_frame) {
   }
 
   cpi->active_arnr_frames = frames_bwd + 1 + frames_fwd;
+
+  // Adjust the strength based on active max q
+  q = ((int)vp9_convert_qindex_to_q(cpi->active_worst_quality) >> 1);
+  if (q > 8) {
+    cpi->active_arnr_strength = cpi->oxcf.arnr_strength;
+  } else {
+    cpi->active_arnr_strength = cpi->oxcf.arnr_strength - (8 - q);
+    if (cpi->active_arnr_strength < 0)
+      cpi->active_arnr_strength = 0;
+  }
+
+  // Adjust number of frames in filter and strength based on gf boost level.
+  if (cpi->active_arnr_frames > (group_boost / 150)) {
+    cpi->active_arnr_frames = (group_boost / 150);
+    cpi->active_arnr_frames += !(cpi->active_arnr_frames & 1);
+  }
+  if (cpi->active_arnr_strength > (group_boost / 300)) {
+    cpi->active_arnr_strength = (group_boost / 300);
+  }
 }
 
 // Analyse and define a gf/arf group .
@@ -1655,7 +1677,7 @@ static void define_gf_group(VP9_COMP *cpi, FIRSTPASS_STATS *this_frame) {
     cpi->gfu_boost = calc_arf_boost(cpi, 0, (i - 1), (i - 1), &f_boost, &b_boost);
     cpi->source_alt_ref_pending = TRUE;
 
-    configure_arnr_filter(cpi, this_frame);
+    configure_arnr_filter(cpi, this_frame, cpi->gfu_boost);
   } else {
     cpi->gfu_boost = (int)boost_score;
     cpi->source_alt_ref_pending = FALSE;

vp9/encoder/vp9_onyx_if.c

@@ -2727,10 +2727,6 @@ static void encode_frame_to_data_rate(VP9_COMP *cpi,
   else
     cpi->zbin_mode_boost_enabled = TRUE;
 
-  if (cpi->gfu_boost <= 400) {
-    cpi->zbin_mode_boost_enabled = FALSE;
-  }
-
   // Current default encoder behaviour for the altref sign bias
   if (cpi->source_alt_ref_active)
     cpi->common.ref_frame_sign_bias[ALTREF_FRAME] = 1;

vp9/encoder/vp9_onyx_int.h

@@ -416,6 +416,7 @@ typedef struct VP9_COMP {
   int max_gf_interval;
   int baseline_gf_interval;
   int active_arnr_frames;           // <= cpi->oxcf.arnr_max_frames
+  int active_arnr_strength;         // <= cpi->oxcf.arnr_max_strength
 
   int64_t key_frame_count;
   int prior_key_frame_distance[KEY_FRAME_CONTEXT];

vp9/encoder/vp9_rdopt.c

@@ -284,9 +284,6 @@ void vp9_initialize_rd_consts(VP9_COMP *cpi, int qindex) {
           (cpi->RDMULT * rd_iifactor[cpi->twopass.next_iiratio]) >> 4;
   }
 
-  if (cpi->RDMULT < 7)
-    cpi->RDMULT = 7;
-
   cpi->mb.errorperbit = (cpi->RDMULT / 110);
   cpi->mb.errorperbit += (cpi->mb.errorperbit == 0);
 

vp9/encoder/vp9_temporal_filter.c

@@ -381,10 +381,8 @@ void vp9_temporal_filter_prepare(VP9_COMP *cpi, int distance) {
   int frames_to_blur = 0;
   int start_frame = 0;
 
-  int strength = cpi->oxcf.arnr_strength;
+  int strength = cpi->active_arnr_strength;
-
   int blur_type = cpi->oxcf.arnr_type;
-
   int max_frames = cpi->active_arnr_frames;
 
   num_frames_backward = distance;