swscale: yuv2422_2_c_template() add cliping.

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

libswscale/output.c

@@ -499,6 +499,13 @@ yuv2422_2_c_template(SwsContext *c, const int16_t *buf[2],
         int U  = (ubuf0[i]        * uvalpha1 + ubuf1[i]        * uvalpha) >> 19;
         int V  = (vbuf0[i]        * uvalpha1 + vbuf1[i]        * uvalpha) >> 19;
 
+        if ((Y1 | Y2 | U | V) & 0x100) {
+            Y1 = av_clip_uint8(Y1);
+            Y2 = av_clip_uint8(Y2);
+            U  = av_clip_uint8(U);
+            V  = av_clip_uint8(V);
+        }
+
         output_pixels(i * 4, Y1, U, Y2, V);
     }
 }