Well, the teletext descriptor has been added to
the PMT (that is the table that defines the PIDs
for the video, audio and PCR elementary streams
for a program). Now when I press the teletext button
on the remote it goes into teletext mode and waits.
Before it just said "service not available".
Next I have to figure out the format of the Teletext
PES packets so I can load some pages.
OpenCaster has an application that generate a PES
packet from a text file. That would be an easy way
to add the pages but when I tried it I could not
get it to work. More research needed.