[mythtv-users] Suggestion: Splicing channels.

Nicholas McCoy mccoyn at gmail.com
Sat Apr 23 18:10:36 UTC 2005


Once you define the block you need, there really shouldn't be any need
to decode any more of the video.  I'm not sure how much this could
save, but it seems a waste to have the computer to struggle when I
only want 10% of the video.  In fact, for software encoders it
shouldn't be encoded at all since there is little use for a non-live
(or close to live) crawl.  I've thought about this a bit, because I
rely on a PVR 350 for my output.  Perhaps it would be possible to play
the crawl as an overlay like the on screen display.  This would of
course all have to be done in software.

On 4/23/05, Joe Votour <joevph at yahoo.com> wrote:
> Part of it is who would care, but also, from a
> technical standpoint, it's very difficult to do.
> 
> First of all, you need multiple inputs.  So, you'd
> need two capture devices (one per channel).  If you're
> using software capture, that requires a lot of CPU
> (about 1GHz per tuner, according to the official
> MythTV documentation).  If you're using hardware
> MPEG-2 capture, that helps on the capture, but you
> still get screwed over on the playback.
> 
> In order to playback that data though, you have to
> make a composite screen of the two sources, and that's
> where it gets tricky.  I don't know the internal
> workings of the MythTV MPEG-2 playback engine, but I
> can say that it will require a fair amount of CPU to
> combine the streams (because processing has to be done
> on each stream to determine what parts to cut out and
> leave in).  (Even if you have a PVR-350 for output,
> this part is required, because you have to feed a
> contiguous signal to the decoder, which means
> pre-processing in software).
> 
> So, to do this, I'd say that you're looking at a
> minimum of a 2GHz machine (for all hardware encoding),
> and you'd be unable to use two tuners for anything
> else.  Probably not worth it for the average person
> (heck, I'm a baseball junkie, and I get enough of it
> by just watching a game, and monitoring the ticker on
> the screen - I have yet to use PiP for that purpose).
> 
> -- Joe
> 
> --- Kyle Rose <krose+mythtv at krose.org> wrote:
> > Nicholas McCoy wrote:
> > > Well, the NFL draft is today and the folks on ESPN
> > are yakking on.
> > > Now, the most important information on that
> > channel is the bottom
> > > couple inches.  I'd like to watch something else
> > on most of the TV.
> > > It would be nice if I could take the bottom couple
> > inches off one
> > > channel and watch on another.  Of course, this
> > feature would work for
> > > sports, stocks and news as well.  Does anyone else
> > think this feature
> > > would be worth implementing.  Also any ideas of
> > how to implement it.
> >
> > Not to muddy the discussion, but what the hell...
> >
> > In general, it'd be great to be able to combine or
> > select from among
> > multiple inputs in some way more interesting than
> > picture-in-picture.
> > For example, the way I watch baseball is generally
> > to turn on the TV,
> > mute it, and then put on the radio broadcast, since
> > the radio announcers
> > are typically much better than the TV announcers.
> >
> > Unfortunately, this doesn't work out so well when
> > one wants to
> > synchronize the sources, as the TV will always be
> > 3-4 seconds behind the
> >  radio broadcast.
> >
> > I can do something like this if I use MLB's Gameday
> > Audio to listen,
> > because I can insert almost any delay I want into
> > that; but it's kinda
> > ugly to have to do this when I could accomplish much
> > the same thing with
> > input selection and a radio tuner module.
> >
> > Anyway, I digress.  Being able to grab the crawl
> > (or, really, any fixed
> > block) out of one recording and superimpose it over
> > another recording
> > would be neat, but I don't know how many people
> > would care.
> >
> > Cheers,
> > Kyle
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