[mythtv] Subtitles problem

[Marco Coli]

Hello,

with DVB-S subtitles I have problems on some channels.

They work without problems on free channels (like RAI, I live in Italy).

They do not appears on encrypted channels (like SkyCinema).

Subtitles are present on these channels, because if I transfer my 
subscriber card out of DVB-S card/CAM and i put it in the CAM of a 
regular set top box, I see subtitles correctly on these channels (as a 
matter of fact I see subtitles on stb also without the card, in this 
case on a black screen, they appear to be in clear).

On these channels, my STB says there are DVB subtitles AND TTX 
subtitles, and they both work. None on myth.

Is this the supposed behaviour?

Thank you
Marco Coli