avfilter/vf_fieldmatch: use correct subsamplings for y0a, y1a and startx

Signed-off-by: Paul B Mahol <onemda@gmail.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/libavfilter/vf_fieldmatch.c b/libavfilter/vf_fieldmatch.c
index 3694f26d33..4f10ed7ccd 100644
--- a/libavfilter/vf_fieldmatch.c
+++ b/libavfilter/vf_fieldmatch.c
@@ -503,9 +503,9 @@ static int compare_fields(FieldMatchContext *fm, int match1, int match2, int fie
         int prvf_linesize, nxtf_linesize;
         const int width  = get_width (fm, src, plane);
         const int height = get_height(fm, src, plane);
-        const int y0a = fm->y0 >> (plane != 0);
-        const int y1a = fm->y1 >> (plane != 0);
-        const int startx = (plane == 0 ? 8 : 4);
+        const int y0a = fm->y0 >> (plane ? fm->vsub : 0);
+        const int y1a = fm->y1 >> (plane ? fm->vsub : 0);
+        const int startx = (plane == 0 ? 8 : 8 >> fm->hsub);
         const int stopx  = width - startx;
         const uint8_t *srcpf, *srcf, *srcnf;
         const uint8_t *prvpf, *prvnf, *nxtpf, *nxtnf;