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vp9: Screen-content after slide-change: increase refresh rate

For screen-content real-time CBR mode: on a detected slide change
that is encoded at max Q (to prevent excessive overshoot), increase
the perc_refresh in the cyclic refresh following the slide change.
Use counter to increase refresh up to some #frames from slide change.

This is attempt to increase quality ramp-up after slide change without
causing too much excess overshoot.

Change-Id: Ie4ec4361082803a522f4a8794b3bb0178c9cf307

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

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

@@ -39,6 +39,7 @@

   }

   assert(MAXQ <= 255);

   memset(cr->last_coded_q_map, MAXQ, last_coded_q_map_size);

+  cr->counter_encode_maxq_scene_change = 0;

   return cr;

 }

@@ -466,6 +467,9 @@

   // TODO(marpan): Consider increasing refresh rate after slide change.

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

     cr->percent_refresh = 10;

+    // Increase the amount of refresh on scene change that is encoded at max Q,

+    // increase for a few cycles of the refresh period (~30 frames).

+    if (cr->counter_encode_maxq_scene_change < 30) cr->percent_refresh = 15;

     cr->rate_ratio_qdelta = 2.0;

     cr->rate_boost_fac = 10;

   }

@@ -533,6 +537,7 @@

              cm->mi_rows * cm->mi_cols * sizeof(*cr->last_coded_q_map));

       cr->sb_index = 0;

       cr->reduce_refresh = 0;

+      cr->counter_encode_maxq_scene_change = 0;

     }

     return;

   } else {

@@ -539,6 +544,7 @@

     int qindex_delta = 0;

     int qindex2;

     const double q = vp9_convert_qindex_to_q(cm->base_qindex, cm->bit_depth);

+    cr->counter_encode_maxq_scene_change++;

     vpx_clear_system_state();

     // Set rate threshold to some multiple (set to 2 for now) of the target

     // rate (target is given by sb64_target_rate and scaled by 256).

@@ -606,6 +612,7 @@

   cr->sb_index = 0;

   cpi->refresh_golden_frame = 1;

   cpi->refresh_alt_ref_frame = 1;

+  cr->counter_encode_maxq_scene_change = 0;

 }

 void vp9_cyclic_refresh_limit_q(const VP9_COMP *cpi, int *q) {

--- a/vp9/encoder/vp9_aq_cyclicrefresh.h

+++ b/vp9/encoder/vp9_aq_cyclicrefresh.h

@@ -68,6 +68,7 @@

   int reduce_refresh;

   double weight_segment;

   int apply_cyclic_refresh;

+  int counter_encode_maxq_scene_change;

 };

 struct VP9_COMP;

--- a/vp9/encoder/vp9_ratectrl.c

+++ b/vp9/encoder/vp9_ratectrl.c

@@ -2809,6 +2809,7 @@

     int enumerator;

     // Force a re-encode, and for now use max-QP.

     *q = cpi->rc.worst_quality;

+    cpi->cyclic_refresh->counter_encode_maxq_scene_change = 0;

     // If the frame_size is much larger than the threshold (big content change)

     // and the encoded frame used alot of Intra modes, then force hybrid_intra

     // encoding for the re-encode on this scene change. hybrid_intra will

-- 

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