hwaccel: fix dxva2 & vaapi loop filter parameters

Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavcodec/dxva2_h264.c

@@ -231,8 +231,8 @@ static void fill_slice_long(AVCodecContext *avctx, DXVA_Slice_H264_Long *slice,
         slice->num_ref_idx_l0_active_minus1 = h->ref_count[0] - 1;
     if (h->list_count > 1)
         slice->num_ref_idx_l1_active_minus1 = h->ref_count[1] - 1;
-    slice->slice_alpha_c0_offset_div2   = h->slice_alpha_c0_offset / 2 - 26;
-    slice->slice_beta_offset_div2       = h->slice_beta_offset     / 2 - 26;
+    slice->slice_alpha_c0_offset_div2   = h->slice_alpha_c0_offset / 2;
+    slice->slice_beta_offset_div2       = h->slice_beta_offset     / 2;
     slice->Reserved8Bits                = 0;
 
     for (list = 0; list < 2; list++) {

libavcodec/vaapi_h264.c

@@ -333,8 +333,8 @@ static int vaapi_h264_decode_slice(AVCodecContext *avctx,
     slice_param->cabac_init_idc                 = h->cabac_init_idc;
     slice_param->slice_qp_delta                 = h->qscale - h->pps.init_qp;
     slice_param->disable_deblocking_filter_idc  = h->deblocking_filter < 2 ? !h->deblocking_filter : h->deblocking_filter;
-    slice_param->slice_alpha_c0_offset_div2     = h->slice_alpha_c0_offset / 2 - 26;
-    slice_param->slice_beta_offset_div2         = h->slice_beta_offset     / 2 - 26;
+    slice_param->slice_alpha_c0_offset_div2     = h->slice_alpha_c0_offset / 2;
+    slice_param->slice_beta_offset_div2         = h->slice_beta_offset     / 2;
     slice_param->luma_log2_weight_denom         = h->luma_log2_weight_denom;
     slice_param->chroma_log2_weight_denom       = h->chroma_log2_weight_denom;