lavc/vvc: Fix scaling matrix DC coef derivation

In 7.4.3.20 of H.266 (V3), there are two similarly-named variables: scalingMatrixDcPred and ScalingMatrixDcRec. The old code set ScalingMatrixDcRec, rather than scalingMatrixDcPred, in the first two branches of the conditions on scaling_list_copy_mode_flag[id] and aps->scaling_list_pred_mode_flag[id]. This could lead to decode mismatches in sequences with explicitly-signalled scaling lists. Signed-off-by: Frank Plowman <post@frankplowman.com>
neoxpert · Dec 10, 2024 · 8629306 · 8629306
1 parent 47b1e1b
commit 8629306
Showing 1 changed file with 3 additions and 3 deletions.
diff --git a/libavcodec/vvc/ps.c b/libavcodec/vvc/ps.c
@@ -1113,17 +1113,17 @@ static void scaling_derive(VVCScalingList *sl, const H266RawAPS *aps)
         //dc
         if (id >= SL_START_16x16) {
             if (!aps->scaling_list_copy_mode_flag[id] && !aps->scaling_list_pred_mode_flag[id]) {
-                sl->scaling_matrix_dc_rec[id - SL_START_16x16] = 8;
+                dc += 8;
             } else if (!aps->scaling_list_pred_id_delta[id]) {
-                sl->scaling_matrix_dc_rec[id - SL_START_16x16] = 16;
+                dc += 16;
             } else {
                 const int ref_id = id - aps->scaling_list_pred_id_delta[id];
                 if (ref_id >= SL_START_16x16)
                     dc += sl->scaling_matrix_dc_rec[ref_id - SL_START_16x16];
                 else
                     dc += sl->scaling_matrix_rec[ref_id][0];
-                sl->scaling_matrix_dc_rec[id - SL_START_16x16] = dc & 255;
             }
+            sl->scaling_matrix_dc_rec[id - SL_START_16x16] = dc & 255;
         }
 
         //ac