[mythtv] DVB subtitles and TS->PES decoder

Marcus Metzler mocm at mocm.de
Fri Nov 26 15:45:36 UTC 2004

>>>>> "Jesper" == Jesper S÷rensen <jesper at datapartner.se> writes:

    Jesper> Juha Kuikka skrev:
    >> Hi,
    >> I am in the process of writing DVB subtiele parser, it is
    >> nowhere near ready but I looked at how to best integrate it
    >> into myth.

    Jesper> Great initiative, I would love to see DVB subtitles in
    Jesper> Myth!

    Jesper> As you might already know Taylor Jacob and John Pullan are
    Jesper> currently working on a DVB overhaul for myth so it might
    Jesper> be a good idea to integrate this into their patch, or at
    Jesper> least synchronize the coding so you don't step on each
    Jesper> other's toes too much.
    Jesper> http://www.digitalregime.com/mythdvb/

    Jesper> If you need any hints for how to integrate the subtitles
    Jesper> into myth maybe you could take a look at DTK's HDTV
    Jesper> captions patch: http://www.mrl.nyu.edu/~danielk/mythtv/

    Jesper> Also, Kenneth Aafl°y did some work on DVB subtitles
    Jesper> (teletext I believe) a while ago, and had an experimental
    Jesper> patch but then sadly he gave up before it was
    Jesper> finished. Maybe you can find some useful info in the dev
    Jesper> list, or if the patch is lost I might have it somewhere in
    Jesper> my archives (e-mail me).

    >> First problem I run into is that hte current ts->pes parser in
    >> transform.c does not seem to parse subtitle streams, at least I
    >> cannot get it to output video, audio and subtitle streams, it
    >> seems to ignore the subtitle stream. Does anyone know if this
    >> is possible at all or should I just use my own ts->pes parser
    >> and replace the one in transform.c ?

    Jesper> I think the plan is to eventually drop transform.c
    Jesper> entirely and use a "stripped" (filtered) TS for DVB
    Jesper> instead of a PS. I think that's the way it's done in the
    Jesper> ATSC/HDTV recorder, and it would mean we could share some
    Jesper> code between DVB/ATSC. Using a TS also has some other
    Jesper> benefits, e.g. allowing the use of multiple audio audio
    Jesper> streams (e.g. both PCM & AC3).

I mean you could drop transport.c right now, most of the code in there
is not needed (only about 3-4 routines). Except for section handling,
there should be no difference between DVB and ATSC and for recording
yuo don't even need to look into the TS packets, you just need to
filter for the PIDs. Why are there two code bases for that.
By the way, you can also have more than one audio or video stream in a
program stream. That would be no reason to switch to TS
recording. Much more compelling is the fact that the PS would have to
be properly remuxed. The TS from digital TV sources is already muxed


| Dr. Marcus O.C. Metzler        |                                   |
| mocm at metzlerbros.de            | http://www.metzlerbros.de/        |
 |>>>             Quis custodiet ipsos custodies                 <<<|

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