shithub: libvpx

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vp9-svc: Add QP dependency to thresh_svc_skip_golden.

In nonrd-pickmode: the golden/spatial reference for inter-layer
prediction may be skipped in the mode testing. Add QP dependency
to reduce the threshold for skipping (i.e., check it more often)
at high QP, if the lower layer was encoded at lower QP relative
to the current layer.

At high QP, a better quality lower resolution is more likely to
provide good spatial (inter-layer) prediction.

avgPSNR/SSIM metrics up by ~1% (all clips positive gain or neutral).
Some decrease in encode time (~1-2%) expected at lower bitrates,
for 3 layer SVC.

Change-Id: I9ee0f62d4b10d4ebd30165d378ecfa4399ae5ef1

--- a/vp9/encoder/vp9_pickmode.c

+++ b/vp9/encoder/vp9_pickmode.c

@@ -1488,7 +1488,6 @@

   int skip_ref_find_pred[4] = { 0 };

   unsigned int sse_zeromv_normalized = UINT_MAX;

   unsigned int best_sse_sofar = UINT_MAX;

-  unsigned int thresh_svc_skip_golden = 500;

 #if CONFIG_VP9_TEMPORAL_DENOISING

   VP9_PICKMODE_CTX_DEN ctx_den;

   int64_t zero_last_cost_orig = INT64_MAX;

@@ -1501,6 +1500,17 @@

   int flag_svc_subpel = 0;

   int svc_mv_col = 0;

   int svc_mv_row = 0;

+  unsigned int thresh_svc_skip_golden = 500;

+  // Lower the skip threshold if lower spatial layer is better quality relative

+  // to current layer.

+  if (cpi->svc.spatial_layer_id > 0 && cm->base_qindex > 150 &&

+      cm->base_qindex > cpi->svc.lower_layer_qindex + 15)

+    thresh_svc_skip_golden = 100;

+  // Increase skip threshold if lower spatial layer is lower quality relative

+  // to current layer.

+  else if (cpi->svc.spatial_layer_id > 0 && cm->base_qindex < 140 &&

+           cm->base_qindex < cpi->svc.lower_layer_qindex - 20)

+    thresh_svc_skip_golden = 1000;

   init_ref_frame_cost(cm, xd, ref_frame_cost);

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

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

@@ -1490,6 +1490,9 @@

   if (cm->frame_type != KEY_FRAME) rc->reset_high_source_sad = 0;

   rc->last_avg_frame_bandwidth = rc->avg_frame_bandwidth;

+  if (cpi->use_svc &&

+      cpi->svc.spatial_layer_id < cpi->svc.number_spatial_layers - 1)

+    cpi->svc.lower_layer_qindex = cm->base_qindex;

 }

 void vp9_rc_postencode_update_drop_frame(VP9_COMP *cpi) {

--- a/vp9/encoder/vp9_svc_layercontext.h

+++ b/vp9/encoder/vp9_svc_layercontext.h

@@ -103,6 +103,8 @@

   int first_layer_denoise;

   int skip_enhancement_layer;

+

+  int lower_layer_qindex;

 } SVC;

 struct VP9_COMP;