[mythtv-users] DVB EPG in MythTV?

[Jakob Fix]

Joe,

Wow!  I was looking for some starting points to better understand DVB
(multiplex, PID, TS, PS, EIT, EPG, etc.), but your explanation of EIT
is very succinct and useful.  Thanks so much!

I live in France, but watch German and UK telly (might give you an
indication about quality of TV here in France ...), and I found the
German guide data to be rather good, at least compared to the UK.

On 26/11/05, Joe Votour <joevph at yahoo.com> wrote:
> Newer SVN versions of MythTV apparently do support
> pulling in data from the DVB program descriptors (I
> live in North America, where DVB isn't available, so I
> can't comment on how well it works).  I have done some
> DVB-related work for my employer though, so I do know
> how the system works.
>
> The EIT is the "Event Information Table" (if I
> remember my TLAs correctly).  The DVB specification
> supports sending lots (and I mean lots) of information
> within it (the basics such as show start/end times,
> program name and genre, but also things like complete
> cast lists, MPEG format information, etc.).
>
> The way it works is that within the MPEG-2 stream that
> is received by your DVB card, there are video, audio
> and PCR (timing) PIDs for one or many "channels",
> there are extra PIDs that are added in by your
> provider (or may come from the original satellite feed
> - regardless of how they got there, they are there).
> A DVB card can listen on these PIDs and capture/parse
> the data, and turn it into program guide entries.
> Most of it is TLV-type (type, length, value) data with
> a fair amount of ASCII text.
>
> As I said, I don't know the specifics of the EIT
> processing within MythTV, but I would suggest that you
> stick with the tv_grab programs if you get accurate
> data from them.  The reasons that I suggest this are:
> 1. With the DVB streams that I have seen, the program
> guide information within the DVB stream is only good
> for 1-2 hours (typically, you get the "now" and
> "next", the currently showing program, and the next
> program).  This means that it will be difficult to
> plan far ahead in the future for scheduling, since the
> data just won't be there.

Question: if I'm using tv_grab_dvb which indeed does retrieve EIT data
from the current stream, this is the same as what's being used by the
builtin MythTV processor, right?

> 2. In order to get complete EIT data, your DVB card
> will likely need to hit multiple frequencies to
> capture the EIT data on those frequencies.  If you
> have a single card and aren't recording, this won't be
> an issue, but if you're recording back to back shows
> and only have a single card, you've got nothing to
> tune to other frequencies to find the EIT data.  In
> that case, you're missing program guide listings.

But that's only a problem while watching Live TV or while recording. 
Whenever I'm not doing one or the other, MythTV could go and fetch
guide data, probably listening or watching whether Live TV or
recording takes place, and pause the retrieval of guide data.

Well, thanks again for your very useful response.

> Again, this information doesn't come from the MythTV
> implementation (I've implemented this in the past, and
> it's quite painful), but comes from my knowledge in
> the area.  YMMV, depending on what kind of hardware
> you have, and how much program data you want (I'm
> quite happy with DataDirect, and having about 10 days
> worth of listings).
>
> -- Joe

--
cheers,
Jakob.

> --- Jakob Fix <jakob.fix at gmail.com> wrote:
>
> > Hello,
> >
> > I've heard that Myth should be capable by now to
> > retrieve EPG data
> > from the DVB stream.  There seems to be quite some
> > talk on the dev
> > list.
> >
> > Is this correct?  If so, which version of Myth
> > should one have in
> > order for this to work?
> >
> > So far I'm using tv_grab_dvb which works fine
> > although it has some
> > problems with timezones, and it only gets the
> > current channel's
> > transport stream's EPG data.
> >
> > Oh, and what does EIT mean, and what's the
> > difference with EPG
> > (wikipedia was no help here)?
> >
> > --
> > cheers,
> > Jakob.