[mythtvnz] Overlapped recordings on ivtv cards?

[Steve Hodge]

On Mon, Nov 23, 2009 at 4:15 PM, Nick Rout <nick.rout at gmail.com> wrote:

> On Mon, Nov 23, 2009 at 3:48 PM, Steve Hodge <stevehodge at gmail.com> wrote:
> > On Mon, Nov 23, 2009 at 10:56 AM, Dr. David J. Knowles
> > <dknowles at clearfield.com> wrote:
> >>
> >> Soft padding is a global setting (set in Setup->TV
> >> Settings->General->Advanced).
> >> In this page you can set before recording time and after recording time
> >> values. Soft padding
> >> is added onto all programs recorded IF POSSIBLE. If the padding is not
> >> possible it is ignored.
> >> One example of soft padding being ignored is for adjacent recordings.
> >> Adjacent recordings
> >> stop at the moment the scheduled program ends. This leads to the
> problems
> >> with the end
> >> of programs appearing on the next recording.
> >
> > My understanding (and I may be out-of-date so please correct me if I'm
> > wrong) is that soft padding is applied after the schedule is determined.
> > This means that if you use soft padding and have two tuners capable of
> > recording the two adjacent shows then the padding will not be applied and
> > the shows will both be recorded on the same tuner. This is less than
> ideal,
> > particularly for people who have say analogue Sky on one tuner and then
> DVB
> > multirec on another - the soft padding will be lost on shows on Freeview
> > unnecessarily.
> >
> > If Mythbusters is the only case where this issue is coming up frequently,
> > just let it record another showing: both the current season and the
> earlier
> > season repeats are shown multiple times per week.
> >
> > It'd be great if the scheduler were able to handle padding better.
> > Unfortunately it's not as simple as it first seems and the scheduler
> itself
> > is a complicated piece of code. That's why multirec is implemented the
> way
> > it is - having "virtual tuners" may be a bit of a hack (with its
> unnecessary
> > requirement of pre-determining how many you might need), but it meant it
> > could be implemented without a lot of changes to the scheduler. I believe
> > there's been one aborted attempt to get the scheduler handling padding
> > better, so I suspect it'll be a while before anyone tries again.
>
> I guess it would theoretically possible to back-to-back on same
> analogue channel by writing the stream during the overlap period to
> two files. Kind of like the tee command works in a shell. However this
> could only work on the SAME channel and would obviously involve a lot
> of coding.
>

Yes. Of course the same-channel case is the one that's interesting here as
soft padding already does the best possible thing with collisions between
shows on different channels.

So far the split-stream idea hasn't happened because it's generally cheap
and easy to add another card (which has the huge benefit of being useful in
situations where the two overlaping shows aren't on the same channel). Maybe
this idea will look more attractive to developers as PCI slots get more
scarce. I suspect though that the more likely outcome is that USB devices
will take over (perhaps PCIe cards will appear as demand for them increases
but there's little sign of that yet). OTOH it could be that a lot of the
work is already done in the form of DVB multirec.

Ironically the analogue codebase may get some serious attention as the
> result of the US switching over. For many US users the only way to use
> myth is via an analogue encoder plugged into a STB.
>

Having to buy or hire an extra STB for each tuner card will make certainly
help encourage developers to do all they can to maximise use of existing
tuners. But if these STBs are being sold stand-alone then they'll probably
start to come with multiple tuners (as the HDHomeRun already does), and
that'll mean the answer will tend back to "buy another tuner card".

Cheers,
Steve
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