[mythtv-users] DVB-T slow to change channel in 0.18 (ubuntu package)

Randy Robertson rmrobert at usc.edu
Thu Apr 6 10:47:29 UTC 2006


As far as I know, all the TV cards can change channels fast (verify by
using tvtime or some plain tv viewer), the problem is that in order to
have seamless livetv pausing/ff/rw, etc, you are really watching a pre
encoded stream that was saved so you are few seconds behind live, so
changing channels means buffering this up again, and it takes the 2-3
seconds that you are behind live tv when you change channels.

With a hypothetically fast enough computer, I don't see why you can't
dump the video data from the card to shared memory, and have one
thread playing "live" (without anywhere near 2-3seconds delay) and
have another thread doing the encoding.  Then, if you do pause- when
you resume, do so from the encoded version, and when ever you change a
channel go back to the "live" video dump.

The process used to be even slower, since changing channels involved
more overhead with the old ring buffer method. So, if you aren't
already- make sure you are running 0.19.

I'd also be interested in knowing how commerical PVRs, like the TIVO
deal with this issue. I assume they can change channels
instantaneously, but maybe not?

For now, the preferred method for channel "surfing" is to use the OSD
to quickly view channel info, without pressing "enter" until you find
the one you want.  Or use the guide. But of course, you don't know if
the show is on commercial, etc. until you switch.

Even if my method above isn't possible for some reasons I don't
understand, it should be fairly trivial to quickly change channels if
you have two tuners, and don't mind having them both in use on one
channel.  Just encode the channel with one tuner, and watch it "live"
ala tvtime as described above.

On 4/6/06, RoboJ1M <jim.neave at googlemail.com> wrote:
> Damn, thats a shame.
>
> At 33 that's only 100 for 3 tuners!
>
> + 3 free IR receivers and controllers!
>
> Is it a complete no hoper? Meaning that it's a hardware limitation?
>
> J1M.
>
>
>  On 4/6/06, Michael Fox <fox.michael at gmail.com> wrote:
> > On 4/6/06, Jim Neave <jim.neave at googlemail.com> wrote:
> > >
> > > Is that normal?
> > >
> >
> > Its normal.
> >
> > I use VP-3020C tuners and it does the same thing.
> > _______________________________________________
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> > mythtv-users at mythtv.org
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> >
>
>
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