Were the subs in those videos hardcoded? If they were then it was just a text overlay added in a video editor application.
If they were a separate file, then you could use an editor to examine the subtitle line. Some formats have the ability to position subs, although not all players may support this.
eg. For SRT: http://forum.doom9.org/showthread.php?p=470941#post470941
A brief description of the SRT format:
The format has no header, and no
footer. Each subtitle has four parts:
Line 1 is a sequential count of
subtitles, starting with 1.
Line 2 is the start timecode, followed
by the string " --> ", followed by the
end timecode. Timecodes are in the
format HH:MM:SS,MIL (hours, minutes,
seconds, milliseconds). The end
timecode can optionally be followed by
display coordinates (example " X1:100
X2:600 Y1:050 Y2:100"). Without
coordinates displayed, each line of
the subtitle will be centered and the
block will appear at the bottom of the
Lines 3 onward are the text of the
subtitle. New lines are indicated by
new lines (i.e. there's no "\n" code).
The only formatting accepted are the
<b>text</b>: put text in boldface
<i>text</i>: put text in italics
<u>text</u>: underline text <font
color="#00ff00">text</font>: apply green color formatting to the text
(you can use the font tag only to change color)
Tags can be combined (and should be
nested properly). Note that the SubRip
code appears to prefer whole-line
formatting (no underlining just one
word in the middle of a line).
Finally, successive subtitles are
separated from each other by blank