shithub: libvpx

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Add cheap show-buffer operation

Adds the ability to have the decoder show one of the existing reference
frames directly, without having to code it indirectly as a series of
skip blocks.

Change-Id: Ib6c26c5f6a8709863cf304ab890db8559687d25e

--- a/vp9/decoder/vp9_decodframe.c

+++ b/vp9/decoder/vp9_decodframe.c

@@ -926,10 +926,17 @@

   cm->version = vp9_rb_read_bit(rb);

   RESERVED;

+  if (vp9_rb_read_bit(rb)) {

+    // show an existing frame directly

+    int frame_to_show = cm->ref_frame_map[vp9_rb_read_literal(rb, 3)];

+    ref_cnt_fb(cm->fb_idx_ref_cnt, &cm->new_fb_idx, frame_to_show);

+    pbi->refresh_frame_flags = 0;

+    cm->filter_level = 0;

+    return 0;

+  }

   cm->frame_type = (FRAME_TYPE) vp9_rb_read_bit(rb);

   cm->show_frame = vp9_rb_read_bit(rb);

   scaling_active = vp9_rb_read_bit(rb);

-  RESERVED;

   if (cm->frame_type == KEY_FRAME) {

     if (vp9_rb_read_literal(rb, 8) != SYNC_CODE_0 ||

@@ -1038,6 +1045,11 @@

   const int keyframe = pc->frame_type == KEY_FRAME;

   YV12_BUFFER_CONFIG *new_fb = &pc->yv12_fb[pc->new_fb_idx];

+  if (!first_partition_size) {

+    // showing a frame directly

+    *p_data_end = data + 1;

+    return 0;

+  }

   data += vp9_rb_bytes_read(&rb);

   xd->corrupted = 0;

   new_fb->corrupted = 0;

--- a/vp9/encoder/vp9_bitstream.c

+++ b/vp9/encoder/vp9_bitstream.c

@@ -1327,10 +1327,10 @@

   vp9_wb_write_bit(wb, cm->version);

   vp9_wb_write_bit(wb, 0);

+  vp9_wb_write_bit(wb, 0);

   vp9_wb_write_bit(wb, cm->frame_type);

   vp9_wb_write_bit(wb, cm->show_frame);

   vp9_wb_write_bit(wb, scaling_active);

-  vp9_wb_write_bit(wb, 0);

   if (cm->frame_type == KEY_FRAME) {

     vp9_wb_write_literal(wb, SYNC_CODE_0, 8);

-- 

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