[linux-dvb] Re: Driver 0.8.1 and encrypted channels

[Carsten Koch <Carsten.Koch@icem.de>]

Klaus Schmidinger wrote:
....
> So this would mean that one can get the TT of the current channel,
> at the rate delivered from that channel 

correct.

> (don't know if that would be any faster than that of analog TV).

Should be a lot faster. At least with my d-box I had the impression
that teletext pages are coming in ~ 5 times faster than on analog TV.
Of course, I may be mislead, because the d-box also buffers the pages,
which is of course the best approach.


> I guess it wouldn't buffer _all_ pages and allow instant access,
> would it?

Not possible with this technique. The vbi is a constant stream
stransmitted with every frame and has only room for part of one
TT page. With this technique, either the TV set must buffer it or
you must communicate with a device between the TV station and the
TV set to tell it which buffered pages you want to see.


> A solution I would consider better would be to collect the TT pages
> just like the EIT data and have all TT data from all channels
> available and display it via the OSD.

I agree. That would be one concrete implementation of the general
mechanism I described above.


> Maybe you could make the teletext VBI insertion optional, thus
> allowing the OSD to use the memory as it has done up to now?
> Just a thought...

That would be one possible solution.

An idea that I had a few months ago might work a lot better, though.
I described it here but I am afraid people did not fully understand 
it, so I would like to try again:

It seems Ralph has implemented re-insertion now, meaning that
he can put the teletext information into the VBI of the video
signal that comes out of the card's FBAS connector. 
If that is possible, it might also be possible to encode
arbitrary text (i.e. text, that does not come from the TV station
but from an application program) this way. 
Considering the numerous problems we see with the OSD, would it 
not be a perfect solution to simply output of the OSD this way? 
What I mean is: create an API that hands the text of ONE specific 
teletext page over to the driver for re-insertion. 
Please note that teletext is blindingly fast (much faster than 
our currect OSD) when it has to transmit only one page. 
You could leave the TV set in teletext mode and it would
display the "teletext-OSD" if there is any, otherwise it 
would automatically display just the picture.

Would that not solve all the problems with the current OSD
(performance and reliability)?  We would even get a larger
OSD which forces us to page less often. And the old OSD could
go where it belongs: down the drain. Freeing up all of the
memory in the firmware that it required.


Still this may be a kludge. The best solution would of course
be to fix the OSD so it becomes fast and reliable even when
it covers the entire screen. Maybe with his growing experience
in the firmware area, Ralph can even pull this off? Would be
great!


Cheers,

Carsten.


--- 
Info:
To unsubscribe send a mail to listar@linuxtv.org with "unsubscribe linux-dvb" as subject.