Add clamping back to mv projection

Clamping in the motion vector projection calculation is required by spec.
In commit aca57bf3db00c29e90605656f1015561d1d67c2d
a rewrite of the function omitted the clamping. This commit readds the
clamping.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/refmvs.c b/src/refmvs.c
index 2039bed..b554a3c 100644
--- a/src/refmvs.c
+++ b/src/refmvs.c
@@ -184,8 +184,11 @@ static inline union mv mv_projection(const union mv mv, const int num, const int
     assert(num > -32 && num < 32);
     const int dm = div_mult[den];
     const int y = mv.y * num * dm, x = mv.x * num * dm;
-    return (union mv) { .y = (y + 8192 + (y >> 31)) >> 14,
-                        .x = (x + 8192 + (x >> 31)) >> 14 };
+    // Round and clip according to AV1 spec section 7.9.3
+    return (union mv) { // 0x3fff == (1 << 14) - 1
+        .y = iclip((y + 8192 + (y >> 31)) >> 14, -0x3fff, 0x3fff),
+        .x = iclip((x + 8192 + (x >> 31)) >> 14, -0x3fff, 0x3fff)
+    };
 }
 
 static void add_temporal_candidate(const refmvs_frame *const rf,