[mythtv-users] PVR350 TVOUT

[f-myth-users at media.mit.edu]

    > Date: Tue, 19 Jan 2010 03:22:05 -0500
    > From: "Michael T. Dean" <mtdean at thirdcontact.com>

    > Myth can decode and display captions from ivtv-recorded MPEG-2--thus the
    > lack of complaints from people who have PVR-250's and PVR-150's and
    > PVR-500's and no PVR-350's.

Excellent.  (I don't know why I was seeing reports of issues in that
case, but I believed them because I never saw anything out of Myth's
internal captioning---I just assumed it was either buggy or
unimplemented for ivtv and didn't investigate because VBI CC worked
fine for me.  It occurred to me much later that Myth probably wasn't
going to run its internal decoder, get the captions, and overlay them
on the 350's own decode regardless of whether I asked it to,
e.g,. that it would -only- show internal captions if I wasn't using
the 350's decoder---that's a [dare I saw it?] usability bug in that
the UI was presenting me with the option to pick two things at once
that cannot work together and giving me no warning that it wasn't
going to work, even though Myth had all the information it needed to
know that neither T nor the "always display captions" checkbox made
sense if 350 onboard decode was enabled.  But if the internal ivtv CC
decoding works a treat, great, I'll use it when I decomission my 350,
since I'm not going to touch the stable setup until then.)

    > > What's the toolchain here?  Is it automatic, or do people have to set
    > > up user jobs to run cc-srt (or whatever) over the stream?  Does it
    > > work in LiveTV as well?  (LiveTV CC seems to imply a toolchain that
    > > can do continuous conversion on the file being generated, or native
    > > understanding in Myth's internal player of PVR-style VBI CC embedding;

    > We have the latter.

Note that there is recent discussion on the ivtv lists of (someday)
changing ivtv's nonstandard CC embedding to something more standard.
If and when that happens, other tools that do editing of such streams
will be less likely to lose the captions, which will also be nice.
It'll presumably be necessary to leave Myth's understanding of the
nonstandard embeddings around "forever", though, to deal with old
recordings.  (And who knows if the more-standard embedding will
ever actually get implemented, or when.)
	
    > As always, anyone wanting WSS support can add it to Myth.  Until then,

Not the same thing.  True WSS support changes the way the TV scans, so
you don't lose vertical resolution.  Myth doing rescaling still means
the TV is scanning its full height and is wasting some of those
scanlines scanning out lines of black for the letterboxing, leaving
fewer lines for the actual content.  Unless you're saying that Myth
somehow has the ability to tell random video cards how to output the
WSS signal in the appropriate blanking-interval line, but my
understanding was that most modern video cards treated tv-out as an
afterthought and didn't implement many/most of the data streams in
the blanking interval.  (Of course, most people have TV's that don't
support that sort of thing; many Sony WEGAs do.)

I agree that with rare support in analog SDTV's and no point in any
HDTV, the majority probably doesn't see any need for this, but it's
sure nice to have for that dwindling population who -do- have
compatible sets.

    > I haven't watched a TV show (on my TV, at least) without captions
    > enabled since shortly after I started using Myth--and I used PVR-x50's
    > with nvidia video cards for several of those years and have always had
    > Myth decoding the captions and never used my TV to decode them.  Believe
    > me, I will be the last Myth user to forget about captions.

Good!