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lavc/vvc: Fix scaling matrix DC coef derivation

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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>
This commit is contained in:
Frank Plowman 2024-11-28 22:17:26 +00:00 committed by Nuo Mi
parent 47b1e1bd84
commit 8629306627
1 changed files with 3 additions and 3 deletions
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6
libavcodec/vvc/ps.c
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@ -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