[mpeg2-dev] writing user_data() into an elementary stream

[anand m. <kvm...@gm...>]

Hello everyone,
                        I am working on a project using libmpeg2 where I
need to inject an explicit user_data() field with some text ,
after every gop header in the input stream. I could inject the start code 00
00 01 B2 which indicates a user data right after the GOP header is finished
( i.e by looking for the next start code occurrence after the GOP header).
                   *The problem is that i dont know how can i write a simple
text inforamtion right after the start code 00 00 01 B2 in the user_data()
field  ?.* (for example i would like to add something like a closed caption
text describing the GOP) . Can some one help me with some pointers to some
links which say how an user data field can be constructed with simple text.

*also can some one tell me if  there is a player/decoder  which recognizes
the user_data text and displays on the screen along with the video*. I hope
its not out of context with libmpeg2 forum.

thanks in advance,
anand