avcodec/dvdsubdec: Fix off-by-one error

Fix an off-by-one error that causes the height of decoded
subtitles to be too small, thus cutting off the lowest row
of pixels.

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

libavcodec/dvdsubdec.c

@@ -345,7 +345,7 @@ static int decode_dvd_subtitles(DVDSubContext *ctx, AVSubtitle *sub_header,
             w = x2 - x1 + 1;
             if (w < 0)
                 w = 0;
-            h = y2 - y1;
+            h = y2 - y1 + 1;
             if (h < 0)
                 h = 0;
             if (w > 0 && h > 0) {