shithub: libvpx

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vp9: Force hybrid_intra on scene change

For real-time screen content mode: when scene/slide change
is detected and re-encode is decided, force hybrid_intra
mode search if slide change is big and alot of Intra modes
were used. hybrid_intra mode will use rd-based intra mode
search for small blocks.

Overall better PSNR on clip with slide changes, with similar
encoded frame size. Encode time lightly higher on average with
this change.

Change-Id: I503835253b777b9f98d74e75a52a8000b76c310c

--- a/vp9/encoder/vp9_encodeframe.c

+++ b/vp9/encoder/vp9_encodeframe.c

@@ -4340,6 +4340,18 @@

   }

 }

+static void hybrid_search_scene_change(VP9_COMP *cpi, MACROBLOCK *const x,

+                                       RD_COST *rd_cost, BLOCK_SIZE bsize,

+                                       PICK_MODE_CONTEXT *ctx,

+                                       TileDataEnc *tile_data, int mi_row,

+                                       int mi_col) {

+  if (!cpi->sf.nonrd_keyframe && bsize <= BLOCK_8X8) {

+    vp9_rd_pick_intra_mode_sb(cpi, x, rd_cost, bsize, ctx, INT64_MAX);

+  } else {

+    vp9_pick_inter_mode(cpi, x, tile_data, mi_row, mi_col, rd_cost, bsize, ctx);

+  }

+}

+

 static void nonrd_pick_sb_modes(VP9_COMP *cpi, TileDataEnc *tile_data,

                                 MACROBLOCK *const x, int mi_row, int mi_col,

                                 RD_COST *rd_cost, BLOCK_SIZE bsize,

@@ -4377,10 +4389,16 @@

                                 mi_col);

   else if (segfeature_active(&cm->seg, mi->segment_id, SEG_LVL_SKIP))

     set_mode_info_seg_skip(x, cm->tx_mode, rd_cost, bsize);

-  else if (bsize >= BLOCK_8X8)

-    vp9_pick_inter_mode(cpi, x, tile_data, mi_row, mi_col, rd_cost, bsize, ctx);

-  else

+  else if (bsize >= BLOCK_8X8) {

+    if (cpi->rc.hybrid_intra_scene_change)

+      hybrid_search_scene_change(cpi, x, rd_cost, bsize, ctx, tile_data, mi_row,

+                                 mi_col);

+    else

+      vp9_pick_inter_mode(cpi, x, tile_data, mi_row, mi_col, rd_cost, bsize,

+                          ctx);

+  } else {

     vp9_pick_inter_mode_sub8x8(cpi, x, mi_row, mi_col, rd_cost, bsize, ctx);

+  }

   duplicate_mode_info_in_sb(cm, xd, mi_row, mi_col, bsize);

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

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

@@ -3983,6 +3983,7 @@

   // For other cases (e.g., CBR mode) use it for 5 <= speed < 8 for now

   // (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;

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

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

        cpi->oxcf.content == VP9E_CONTENT_SCREEN ||

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

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

@@ -363,6 +363,7 @@

   rc->high_source_sad = 0;

   rc->reset_high_source_sad = 0;

   rc->high_source_sad_lagindex = -1;

+  rc->hybrid_intra_scene_change = 0;

   rc->alt_ref_gf_group = 0;

   rc->last_frame_is_src_altref = 0;

   rc->fac_active_worst_inter = 150;

@@ -2807,6 +2808,26 @@

     int enumerator;

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

     *q = cpi->rc.worst_quality;

+    // 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

+    // use rd-based intra mode selection for small blocks.

+    if (frame_size > (thresh_rate << 1) && cpi->svc.spatial_layer_id == 0) {

+      MODE_INFO **mi = cm->mi_grid_visible;

+      int sum_intra_usage = 0;

+      int mi_row, mi_col;

+      int tot = 0;

+      for (mi_row = 0; mi_row < cm->mi_rows; mi_row++) {

+        for (mi_col = 0; mi_col < cm->mi_cols; mi_col++) {

+          if (mi[0]->ref_frame[0] == INTRA_FRAME) sum_intra_usage++;

+          tot++;

+          mi++;

+        }

+        mi += 8;

+      }

+      sum_intra_usage = 100 * sum_intra_usage / (cm->mi_rows * cm->mi_cols);

+      if (sum_intra_usage > 60) cpi->rc.hybrid_intra_scene_change = 1;

+    }

     // Adjust avg_frame_qindex, buffer_level, and rate correction factors, as

     // these parameters will affect QP selection for subsequent frames. If they

     // have settled down to a very different (low QP) state, then not adjusting

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

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

@@ -181,6 +181,7 @@

   int last_frame_is_src_altref;

   int high_source_sad;

   int count_last_scene_change;

+  int hybrid_intra_scene_change;

   int avg_frame_low_motion;

   int af_ratio_onepass_vbr;

   int force_qpmin;