From af6d8456a337db0361aae0952447490200d0d3b9 Mon Sep 17 00:00:00 2001
From: Marco Paniconi <marpan@google.com>
Date: Tue, 24 Jul 2018 11:34:42 -0700
Subject: [PATCH] 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
---
 vp9/encoder/vp9_encoder.c  | 1 +
 vp9/encoder/vp9_pickmode.c | 4 +++-
 vp9/encoder/vp9_ratectrl.c | 2 ++
 vp9/encoder/vp9_ratectrl.h | 1 +
 4 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/vp9/encoder/vp9_encoder.c b/vp9/encoder/vp9_encoder.c
index de5519dce..ed2c17702 100644
--- a/vp9/encoder/vp9_encoder.c
+++ b/vp9/encoder/vp9_encoder.c
@@ -3985,6 +3985,7 @@ static int encode_without_recode_loop(VP9_COMP *cpi, size_t *size,
   // (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 ||
diff --git a/vp9/encoder/vp9_pickmode.c b/vp9/encoder/vp9_pickmode.c
index 8248d12e6..fa7cf8c26 100644
--- a/vp9/encoder/vp9_pickmode.c
+++ b/vp9/encoder/vp9_pickmode.c
@@ -1827,7 +1827,9 @@ void vp9_pick_inter_mode(VP9_COMP *cpi, MACROBLOCK *x, TileDataEnc *tile_data,
     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;
     }
 
diff --git a/vp9/encoder/vp9_ratectrl.c b/vp9/encoder/vp9_ratectrl.c
index 22ae7266b..9bf845890 100644
--- a/vp9/encoder/vp9_ratectrl.c
+++ b/vp9/encoder/vp9_ratectrl.c
@@ -364,6 +364,7 @@ void vp9_rc_init(const VP9EncoderConfig *oxcf, int pass, RATE_CONTROL *rc) {
   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 @@ int vp9_encodedframe_overshoot(VP9_COMP *cpi, int frame_size, int *q) {
     // 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
diff --git a/vp9/encoder/vp9_ratectrl.h b/vp9/encoder/vp9_ratectrl.h
index 373c6a3aa..cf37117f9 100644
--- a/vp9/encoder/vp9_ratectrl.h
+++ b/vp9/encoder/vp9_ratectrl.h
@@ -190,6 +190,7 @@ typedef struct {
   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;
-- 
2.40.0