avfilter/vf_fieldmatch: Add () to protect the arguments of the HAS_FF_AROUND() macro

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/vf_fieldmatch.c

@@ -285,9 +285,9 @@ static int calc_combed_score(const FieldMatchContext *fm, const AVFrame *src)
             cmkpV  += cmk_linesizeUV;
             cmkpU  += cmk_linesizeUV;
             for (x = 1; x < width - 1; x++) {
-#define HAS_FF_AROUND(p, lz) (p[x-1 - lz] == 0xff || p[x - lz] == 0xff || p[x+1 - lz] == 0xff || \
-                              p[x-1     ] == 0xff ||                      p[x+1     ] == 0xff || \
-                              p[x-1 + lz] == 0xff || p[x + lz] == 0xff || p[x+1 + lz] == 0xff)
+#define HAS_FF_AROUND(p, lz) (p[(x)-1 - (lz)] == 0xff || p[(x) - (lz)] == 0xff || p[(x)+1 - (lz)] == 0xff || \
+                              p[(x)-1       ] == 0xff ||                          p[(x)+1       ] == 0xff || \
+                              p[(x)-1 + (lz)] == 0xff || p[(x) + (lz)] == 0xff || p[(x)+1 + (lz)] == 0xff)
                 if ((cmkpV[x] == 0xff && HAS_FF_AROUND(cmkpV, cmk_linesizeUV)) ||
                     (cmkpU[x] == 0xff && HAS_FF_AROUND(cmkpU, cmk_linesizeUV))) {
                     ((uint16_t*)cmkp)[x]  = 0xffff;