mpegvideo_enc: Fix chroma edge size

Fixes ticket1303
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mpegvideo_enc.c

@@ -1827,11 +1827,11 @@ static av_always_inline void encode_mb_internal(MpegEncContext *s,
         ptr_y = ebuf;
         s->dsp.emulated_edge_mc(ebuf + 18 * wrap_y, ptr_cb, wrap_c, 8,
                                 mb_block_height, mb_x * 8, mb_y * 8,
-                                s->width >> 1, s->height >> 1);
+                                (s->width+1) >> 1, (s->height+1) >> 1);
         ptr_cb = ebuf + 18 * wrap_y;
         s->dsp.emulated_edge_mc(ebuf + 18 * wrap_y + 8, ptr_cr, wrap_c, 8,
                                 mb_block_height, mb_x * 8, mb_y * 8,
-                                s->width >> 1, s->height >> 1);
+                                (s->width+1) >> 1, (s->height+1) >> 1);
         ptr_cr = ebuf + 18 * wrap_y + 8;
     }