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

[Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>]

Ralph Metzler wrote:
> 
> Carsten Koch writes:
>  > Klaus Schmidinger wrote:
>  >
>  > > (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.
> 
> It is not faster, just buffered by the d-box.
> The digital teletext stream should be exactly the same as transmitted
> through analog TV. The packages even specify which VBI line to use.
> They also contain the pages ready for transmission with the right bit
> order, error correction, parity, etc. just as you find them when
> sampling VBI with a frame grabber.
> That's why it is called re-insertion.

I have just loaded the latest CVS driver version and teletext works
just fine with the default 'n-tv' channel (although, as should be expected,
not faster than with terrestrial or analog satellite channels).
I'll have to modify the VDR 'channels.conf' format to be able to store the TT-PIDs.

>  > > 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.
> 
> Setting a PES filter for the teletext PID and decoding it is no problem
> but displaying it with full teletext color depth (4bit?) on the OSD
> might be.

VDR currently uses the OSD in 4bit color mode, and I have found a TT font
that should be usable with the maximum possible resolution the OSD can
provide in that mode.

BTW: Thanks, Ralph, for re-enabling the OSD in the resolution used by VDR :-)

> [...]
>  > 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!
> 
> What exactly are the problems with OSD right now?
> I cannot do anything about the small memory...

Well, apparently you have done something that makes it work again.
VDR works just fine with today's CVS driver. For those who want to
use the latest driver with VDR 0.7, they should apply the following patch
to dvbapi.c:

--- dvbapi.c    2001/01/20 09:52:56     1.52
+++ dvbapi.c    2001/01/23 18:35:13
@@ -2182,7 +2182,8 @@
         freq -= Setup.LnbFrequLo;
      else
         freq -= Setup.LnbFrequHi;
-     front.pnr       = 0;
+     front.channel_flags = Ca ? DVB_CHANNEL_CA : DVB_CHANNEL_FTA;
+     front.pnr       = Pnr;
      front.freq      = freq * 1000000UL;
      front.diseqc    = Diseqc;
      front.srate     = Srate * 1000;

> ...and if you want to
> transmit bitmaps during playback (and thus reducing the available
> bandwidth for the playback) you cannot expect not to get problems.

Maybe I'm wrong, but it appears to me as if the OSD itself is displayed
just fine when used during replay, and that "only" the picture (and sometimes
the sound) is distorted. Would there be any possibility to give the video/audio
data higher priority, allowing them to "flow freely", while the OSD data is only
transferred when there is free capacity? Since I don't know anything about
the internal mechanisms in that area I can only speculate about that.
As a result, the OSD would perhaps be refreshed in several steps, but that
might be more tolerable than a distorted picture or sound.

Just some thoughts...

Klaus
-- 
_______________________________________________________________

Klaus Schmidinger                       Phone: +49-8635-6989-10
CadSoft Computer GmbH                   Fax:   +49-8635-6989-40
Hofmark 2                               Email:   kls@cadsoft.de
D-84568 Pleiskirchen, Germany           URL:     www.cadsoft.de
_______________________________________________________________


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