Signal delta loop filter level between superblocks
For the first superblock, signal a filter level (6 bit).
For other superblocks, signal the delta (3 bit) and sign (1 bit).
To guarantee the delta can be represented by 3 bits, the search
range of current superblock filter level is capped as
curr_lvl = prev_lvl +- ((1 << 3) - 1)
Change-Id: Ibbe2941aa96ec1220ed2adb7edf3d29cb032f0ec
diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index 4019364..d5b9380 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -3131,9 +3131,33 @@
#if CONFIG_LPF_SB
// send filter level for each superblock (64x64)
if (bsize == cm->sb_size) {
- aom_write_literal(
- w, cm->mi_grid_visible[mi_row * cm->mi_stride + mi_col]->mbmi.filt_lvl,
- 6);
+ if (mi_row == 0 && mi_col == 0) {
+ aom_write_literal(
+ w,
+ cm->mi_grid_visible[mi_row * cm->mi_stride + mi_col]->mbmi.filt_lvl,
+ 6);
+ } else {
+ int prev_mi_row, prev_mi_col;
+ if (mi_col - MAX_MIB_SIZE < 0) {
+ prev_mi_row = mi_row - MAX_MIB_SIZE;
+ prev_mi_col = mi_col;
+ } else {
+ prev_mi_row = mi_row;
+ prev_mi_col = mi_col - MAX_MIB_SIZE;
+ }
+ MB_MODE_INFO *curr_mbmi =
+ &cm->mi_grid_visible[mi_row * cm->mi_stride + mi_col]->mbmi;
+ MB_MODE_INFO *prev_mbmi =
+ &cm->mi_grid_visible[prev_mi_row * cm->mi_stride + prev_mi_col]->mbmi;
+
+ const uint8_t curr_lvl = curr_mbmi->filt_lvl;
+ const uint8_t prev_lvl = prev_mbmi->filt_lvl;
+ const int sign = curr_lvl > prev_lvl;
+ const unsigned int delta = abs(curr_lvl - prev_lvl);
+
+ aom_write_literal(w, delta, LPF_DELTA_BITS);
+ if (delta) aom_write_literal(w, sign, 1);
+ }
}
#endif
