[vdr] Anyone working on ttxtsubs for 1.7.4?

Klaus Schmidinger Klaus.Schmidinger at cadsoft.de
Sat Feb 28 11:42:35 CET 2009


On 26.02.2009 12:08, Magnus Hörlin wrote:
> Hi. I've just made the switch to S2API and vdr-1.7.4 and it seems to work
> quite well both with xineliboutput (with vdpau) and streamdev now. The thing
> I'm missing is teletext subtitles and I don't know how hard it would be to
> update it for ts. Has anyone started on this? What countries other than
> Sweden and Finland use teletext subtitles frequently? I understand that it
> is not one of your (Klaus) top priorities, but do you have access to any
> channels that use it? Otherwise it's probably even lower on the priorities
> list.

I believe the German ZDF channel broadcasts both ttxt and DVB subtitles.

> One feature request for VDR: a setup option to record all pids, including
> all audio and teletext pids. That way I guess it would be easier to develop
> a plugin for it (and I'd be happy to send you some recordings).

It already records all audio pids.
I wouldn't want to record the ttxt pid just because of a few bytes for
subtitles. Here's a copy of a message I just sent to Rolf Ahrenberg
privately, after he sent me a suggested patch to record the ttxt pid:

----------------------------------------------------------------------
...teletext subtitles are a thing from the past, the normal way
of broadcasting subtitles should be DVB subtitles. I hardly think a
DVD player would be able to handle teletext subtitles (or am I wrong here?).

I would prefer a solution where the teletext subtitles are converted into
DVB subtitles during recording (and also during live viewing). Then the
rest of VDR would only have to handle one single subtitle format.

I suggest you first write a class that accepts a teletext TS data
stream and outputs a DVB subtitle TS stream. Then we can see how
this can be inserted into the recording chain and during live viewing.
Something like

class cTtxtToDvbSubtitles {
...
public:
  cTtxtToDvbSubtitles(int Page); // the teletext page containing the subtitles
  void PutTtxtTs(uchar *Data, int Length); // put a single TS packet of ttxt data
                                           // into the converter
  uchar *GetDvbTs(int &Length); // get one or more TS packets containing a complete
                                // DVB subtitle page
  ...
  };

What we also need is a way of detecting whether there are any ttxt subtitles,
and on which page they are broadcast (haven't looked into the DVB standard
about this yet, but I believe every broadcaster uses a different page).

Once we have these facilities, this could well go into the core VDR.
----------------------------------------------------------------------


Klaus



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