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vp9: Reduce qp threshold for limiting cyclic refresh on steady blocks.

Makes the delta-qp stop little earlier on areas that have been refreshed enough.
This helps to reduce some pulsing artifact on noisy flat areas observed in some
noisy vc-clips.

Threshold changes only take effect for sources where noise level is estimated to
be >= medium level.

Only affects 1 pass CBR, non-screen content case.

Change-Id: Iacf557f6aa8abbcd6782c02ff2e6c14891960850

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

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

@@ -393,13 +393,18 @@

   cr->target_num_seg_blocks = 0;

   if (cpi->oxcf.content != VP9E_CONTENT_SCREEN) {

     consec_zero_mv_thresh = 100;

-   if (cpi->noise_estimate.enabled && cpi->noise_estimate.level >= kMedium)

-     consec_zero_mv_thresh = 80;

   }

   qindex_thresh =

       cpi->oxcf.content == VP9E_CONTENT_SCREEN

       ? vp9_get_qindex(&cm->seg, CR_SEGMENT_ID_BOOST2, cm->base_qindex)

       : vp9_get_qindex(&cm->seg, CR_SEGMENT_ID_BOOST1, cm->base_qindex);

+  // More aggressive settings for noisy content.

+  if (cpi->noise_estimate.enabled && cpi->noise_estimate.level >= kMedium) {

+    consec_zero_mv_thresh = 80;

+    qindex_thresh =

+        VPXMAX(vp9_get_qindex(&cm->seg, CR_SEGMENT_ID_BOOST1, cm->base_qindex),

+                              7 * cm->base_qindex >> 3);

+  }

   do {

     int sum_map = 0;

     // Get the mi_row/mi_col corresponding to superblock index i.

@@ -463,6 +468,8 @@

     cr->percent_refresh = 5;

   cr->max_qdelta_perc = 50;

   cr->time_for_refresh = 0;

+  cr->motion_thresh = 32;

+  cr->rate_boost_fac = 15;

   // Use larger delta-qp (increase rate_ratio_qdelta) for first few (~4)

   // periods of the refresh cycle, after a key frame.

   // Account for larger interval on base layer for temporal layers.

@@ -472,9 +479,11 @@

     cr->rate_ratio_qdelta = 3.0;

   } else {

     cr->rate_ratio_qdelta = 2.0;

-  if (cpi->noise_estimate.enabled && cpi->noise_estimate.level >= kMedium)

-    // Reduce the delta-qp if the estimated source noise is above threshold.

-    cr->rate_ratio_qdelta = 1.5;

+    if (cpi->noise_estimate.enabled && cpi->noise_estimate.level >= kMedium) {

+      // Reduce the delta-qp if the estimated source noise is above threshold.

+      cr->rate_ratio_qdelta = 1.7;

+      cr->rate_boost_fac = 13;

+    }

   }

   // Adjust some parameters for low resolutions at low bitrates.

   if (cm->width <= 352 &&

@@ -482,9 +491,6 @@

       rc->avg_frame_bandwidth < 3400) {

     cr->motion_thresh = 4;

     cr->rate_boost_fac = 10;

-  } else {

-    cr->motion_thresh = 32;

-    cr->rate_boost_fac = 15;

   }

   if (cpi->svc.spatial_layer_id > 0) {

     cr->motion_thresh = 4;