[NORMATIVE] Fix discrepancy with scaled inter predictors
For sub-8x8-sized chroma blocks, we may be predicting a region
which covers multiple luma blocks - in particular, ones above
or to the left of the current block. This means that we need
to adjust the top-left corner of where we predict from.
This was correctly implemented in the non-scaling code path, but
not in the scaling code path, meaning the chroma predictions could
potentially be 2px off from where they should be when using scaling.
Change-Id: If5b269e64bdfa1d6d4af60d26cc7c1615cb87157
diff --git a/av1/common/reconinter.c b/av1/common/reconinter.c
index 44370a2..8e7c967 100644
--- a/av1/common/reconinter.c
+++ b/av1/common/reconinter.c
@@ -909,10 +909,18 @@
if (is_intrabc) sub8x8_inter = 0;
- sub8x8_inter = sub8x8_inter && !build_for_obmc;
- const int row_start = (block_size_high[bsize] == 4) && ss_y ? -1 : 0;
- const int col_start = (block_size_wide[bsize] == 4) && ss_x ? -1 : 0;
+ // For sub8x8 chroma blocks, we may be covering more than one luma block's
+ // worth of pixels. Thus (mi_x, mi_y) may not be the correct coordinates for
+ // the top-left corner of the prediction source - the correct top-left corner
+ // is at (pre_x, pre_y).
+ const int row_start =
+ (block_size_high[bsize] == 4) && ss_y && !build_for_obmc ? -1 : 0;
+ const int col_start =
+ (block_size_wide[bsize] == 4) && ss_x && !build_for_obmc ? -1 : 0;
+ const int pre_x = (mi_x + MI_SIZE * col_start) >> ss_x;
+ const int pre_y = (mi_y + MI_SIZE * row_start) >> ss_y;
+ sub8x8_inter = sub8x8_inter && !build_for_obmc;
if (sub8x8_inter) {
for (int row = row_start; row <= 0 && sub8x8_inter; ++row) {
for (int col = col_start; col <= 0; ++col) {
@@ -960,12 +968,10 @@
const RefBuffer *ref_buf =
&cm->frame_refs[this_mbmi->ref_frame[ref] - LAST_FRAME];
- const int c_offset = (mi_x + MI_SIZE * col_start) >> ss_x;
- const int r_offset = (mi_y + MI_SIZE * row_start) >> ss_y;
pd->pre[ref].buf0 =
(plane == 1) ? ref_buf->buf->u_buffer : ref_buf->buf->v_buffer;
pd->pre[ref].buf =
- pd->pre[ref].buf0 + scaled_buffer_offset(c_offset, r_offset,
+ pd->pre[ref].buf0 + scaled_buffer_offset(pre_x, pre_y,
ref_buf->buf->uv_stride,
&ref_buf->sf);
pd->pre[ref].width = ref_buf->buf->uv_crop_width;
@@ -975,7 +981,9 @@
const struct scale_factors *const sf =
is_intrabc ? &cm->sf_identity : &ref_buf->sf;
struct buf_2d *const pre_buf = is_intrabc ? dst_buf : &pd->pre[ref];
+
const MV mv = this_mbmi->mv[ref].as_mv;
+
uint8_t *pre;
int xs, ys, subpel_x, subpel_y;
const int is_scaled = av1_is_scaled(sf);
@@ -986,9 +994,9 @@
if (is_scaled) {
int ssx = pd->subsampling_x;
int ssy = pd->subsampling_y;
- int orig_pos_y = (r_offset + y) << SUBPEL_BITS;
+ int orig_pos_y = (pre_y + y) << SUBPEL_BITS;
orig_pos_y += mv.row * (1 << (1 - ssy));
- int orig_pos_x = (c_offset + x) << SUBPEL_BITS;
+ int orig_pos_x = (pre_x + x) << SUBPEL_BITS;
orig_pos_x += mv.col * (1 << (1 - ssx));
int pos_y = sf->scale_value_y(orig_pos_y, sf);
int pos_x = sf->scale_value_x(orig_pos_x, sf);
@@ -1066,9 +1074,9 @@
// plane, then project into the reference frame
int ssx = pd->subsampling_x;
int ssy = pd->subsampling_y;
- int orig_pos_y = (mi_y << (SUBPEL_BITS - ssy)) + (y << SUBPEL_BITS);
+ int orig_pos_y = (pre_y + y) << SUBPEL_BITS;
orig_pos_y += mv.row * (1 << (1 - ssy));
- int orig_pos_x = (mi_x << (SUBPEL_BITS - ssx)) + (x << SUBPEL_BITS);
+ int orig_pos_x = (pre_x + x) << SUBPEL_BITS;
orig_pos_x += mv.col * (1 << (1 - ssx));
int pos_y = sf->scale_value_y(orig_pos_y, sf);
int pos_x = sf->scale_value_x(orig_pos_x, sf);
