shithub: libvpx

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vp9: Modify logic for flat blocks in nonrd-pickmode.

For real-time screen content mode: when slide change
is detected, for spatially flat blocks (source_variance = 0) on
the re-encoded frame, skip inter modes (so force intra) if
non-zero temporal variance is detected for the coding block.
Add flag to keep track of re-encoded frame at max Q.
Reduces artifacts on slide change.

Change-Id: I28151f412aba6ab8cb03f30087c7ce16d443654b

--- a/vp9/encoder/vp9_encoder.c

+++ b/vp9/encoder/vp9_encoder.c

@@ -3985,6 +3985,7 @@

   // (need to check encoding time cost for doing this for speed 8).

   cpi->rc.high_source_sad = 0;

   cpi->rc.hybrid_intra_scene_change = 0;

+  cpi->rc.re_encode_maxq_scene_change = 0;

   if (cm->show_frame && cpi->oxcf.mode == REALTIME &&

       (cpi->oxcf.rc_mode == VPX_VBR ||

        cpi->oxcf.content == VP9E_CONTENT_SCREEN ||

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

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

@@ -1827,7 +1827,9 @@

     if (!(cpi->ref_frame_flags & flag_list[ref_frame])) continue;

     if (sf->short_circuit_flat_blocks && x->source_variance == 0 &&

-        frame_mv[this_mode][ref_frame].as_int != 0) {

+        (frame_mv[this_mode][ref_frame].as_int != 0 ||

+         (svc->spatial_layer_id == 0 && cpi->rc.re_encode_maxq_scene_change &&

+          !x->zero_temp_sad_source))) {

       continue;

     }

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

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

@@ -364,6 +364,7 @@

   rc->reset_high_source_sad = 0;

   rc->high_source_sad_lagindex = -1;

   rc->hybrid_intra_scene_change = 0;

+  rc->re_encode_maxq_scene_change = 0;

   rc->alt_ref_gf_group = 0;

   rc->last_frame_is_src_altref = 0;

   rc->fac_active_worst_inter = 150;

@@ -2813,6 +2814,7 @@

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

     *q = cpi->rc.worst_quality;

     cpi->cyclic_refresh->counter_encode_maxq_scene_change = 0;

+    cpi->rc.re_encode_maxq_scene_change = 1;

     // 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

--- a/vp9/encoder/vp9_ratectrl.h

+++ b/vp9/encoder/vp9_ratectrl.h

@@ -190,6 +190,7 @@

   int high_source_sad;

   int count_last_scene_change;

   int hybrid_intra_scene_change;

+  int re_encode_maxq_scene_change;

   int avg_frame_low_motion;

   int af_ratio_onepass_vbr;

   int force_qpmin;