[mythtv] Re: State of DVB ATSC

Taylor Jacob rtjacob at earthlink.net
Mon Mar 28 15:17:12 UTC 2005


Quoting Doug Larrick <doug at ties.org>:

> I'm thinking of the code to assemble TS packets into higher-level
> packets, and to do the packet filtering and state tracking.  Not a
> deficiency in Myth at all... I think much of the functionality in the
> DVB *drivers* should/could have been a standard userspace library
> instead.  I'm just rambling here; not suggesting any action.

If you mean section re-assmembly that *IS* done by the drivers, and should be
since you have to request that section data get reassembled..  Packet filtering
is also done by the drivers simply based on PID..  Tracking of Continuity
counters is not..

> >>* You need to finish hooking up the STT parser to get the GPS offset.
> >>GPS *will* add another leap second eventually, and the PSIP times will
> >>no longer line up properly.  Unfortunately this means delaying
> >>processing any PSIP guide entries until it's set.  In my homegrown PSIP
> >>parser I keep EIT/ETT entries in a queue until we've seen MGT, VCT, and
> >>STT.  But you could just as easily discard them since they'll be around
> >>again soon enough.
> > This is already done.. The STT is a prerequisite of the EIT in the
> > TableHandler[] class.. The TableHandler[] class has all of the
> prerequisutes
> > for each table built in, so it makes siparser not look so complicated.. But
> for
> > example PAT is mandatory before PMT.. VCT and STT before EIT, etc..
> As of when?  Last couple weeks?  When I last looked at the code it was
> present but actually setting the member variable was commented out for
> some reason.

Initial Import of siparser.. Look at line 2389.. Its been there for forever..

> That would break current hdtvrecorder completely... no caching.  Then
> there's the issue of whether the engineering staff is allowed time to
> look at HDTV issues when it's so little (but growing) of the audience.
> We're lucky in Boston that a couple of the stations have real tech-heads
> for head engineers :-)

Well no one cares about digital tv really.. Its a financial burden right now,
and will continue to be until they are forcibly swiched off of analog, so
seeing stuff like this get fixed quickly by the broadcasters will not happen
anytime soon..

> Glad to hear PS is being deprecated... TS is much more flexible.  I
> agree ffmpeg is a big ol' heap of code.  Have you asked specific
> questions on the mythtv-dev list?  Of the HDTV guys, I know at least
> Daniel and I have poked in there at one point or another.  And of course
> it seems every time I've seen a playback bug in ffmpeg core and
> mentioned it, Isaac has gone away for about a microsecond and come back
> with a fix :-)

No I haven't asked on the list yet, and really don't plan on it.. I just need
some more time with the code to not ask stupid questions..

> > They always have worked like a champ.. :)  I do all of my testing in
LiveTV..
> > Recording is such a simplier case
> Even when faced with poor signal quality or missing subchannels?

Any issue with changing channels with poor signal or an invalid channel is a
problem with the frontend and affects the v4l code as well as the dvb based
code..

> >>* Does recording capture PCR on channels where it's on a separate PID?
> > Its supposed to.. Do you have any channels there that are like this?  I
> have
> > gotten some complaints about it not working, but the only thing I can find
> to
> > blame it at this point is mpegts.c..  If you do i'd love to get you to do
> some
> > testing..
> I do not.  John Poet does, or did at one point.

John Poet.. Still have this present in your market?  Have you tried the DVB
drivers and TS mode?


Taylor



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