spumux: not add subtitle

[soongwoo]

spumux does not add subtitle in mpeg2 file.
Interestingly, the output is bigger than input.
That means the subtitle is added!
But, the subtitle is not shown with mplayer, totem-xine at all.
Is there anyone to point out why it does not work?

command: spumux -s0 subtitle.NTSC.xml < 01of11.From.Pole.To.Pole.NTSC.mpg >
01of11.From.Pole.To.Pole.NTSC.sub.mpg

The output from the command:
DVDAuthor::spumux, version 0.6.14.
Build options: gnugetopt magick iconv freetype
Send bugs to <dvdauthor-users@lists.sourceforge.net>

INFO: Locale=en_US.UTF-8
INFO: Converting filenames to UTF-8
INFO: Detected subtitle file format: subviewer
INFO: Opened iconv descriptor. *UTF-8* *ISO8859-1*
INFO: Read 366 subtitles
INFO: Adjusted 140 subtitle(s).
INFO: Unicode font: 2601 glyphs.
WARN:spacewidth set to default.
INFO: Found EOF in .sub file.
INFO: 324 subtitles added, 0 subtitles skipped, stream: 32, offset: 0.18

Statistics:
- Processed 324 subtitles.
- The longest display line had 50 characters.
- The maximum number of displayed lines was 2.
- The normal display height of the font segoeui.ttf was 24.
- The bottom display height of the font segoeui.ttf was 30.
- The biggest subtitle box had 2092 bytes.

Here is subtitle.NTSC.xml:
<subpictures>
<stream>
<textsub filename="01of11.From.Pole.To.Pole.srt"
characterset="ISO8859-1"
fontsize="18.0" font="segoeui.ttf"
horizontal-alignment="center"
vertical-alignment="bottom"
left-margin="60" right-margin="60"
top-margin="20" bottom-margin="30"
subtitle-fps="29.97" movie-fps="25.97"
movie-width="720" movie-height="472"/>
</stream>
</subpictures>