[mythtv-users] capture card

[MythTV]

> Tom Furie wrote:
> > What I don't understand with multirec is why the number of
> simultaneous
> > recordings is limited. Surely, if you're tuned to one mux, you
should
> be
> > able to record everything that is coming across on that frequency?
In
> > theory that would mean that here in the UK, you could record
> everyhing
> > on Freeview with six physical tuners. I'm not sure how many more
> would
> > be needed for Freesat.
> I am out of my area of expertise here, but I suspect that you would be
> limited by bus, or disk, IO capability, since each stream would be
> recording to disk as different files.


When I used 'webscheduler' (a java application) under windows, it was
able to 
open a tuner, start receiving a "Full TS" stream, meaning all transport
streams,
(all "channels") on a particular multiplex.

It could then split out individual streams and create multiple
concurrent
recordings including overlap etc, all from a single "Full TS" input
stream.
(I'm not 100% sure of the terminology here)

Myth, in its pre 1.0 release state, has chosen to handle multiple
transport streams
and multiple overlapping recordings by creating 'virtual tuners' which
accept data
fed from a physical tuner.

I personally have four physical tuners, and in the tuner properties have
defined four (4)
"virtual tuners" (again, unsure of the exact terminology) in order to
allow overlapped
recordings and multiple streams (ABC1 ABC2 and ABC3 for example).

Now, technically, to support the overlapped recordings on the channel 2
(ABC) multiplex, I would
need up to 6 "virtual" tuners (2 for each ABC1 ABC2 and ABC3, assuming
ABC HD shows the same content as ABC 1)..
Thus allowing an entire block of programs to be recorded.

Furthermore, if my recording schedules specified, say 15 minutes beyond
the end of the show,
and I recorded a 10 minute kids show between two other shows, it is
possible I may in fact need
three "virtual" tuners per channel, therefore 9 virtual tuners per card.

Now, with four cards, I potentially have 36 virtual tuners..

In reality I have 16 virtual tuners.. would increasing that to 36 cause
problems???
They are never all in use, just potentially usable..

> I am out of my area of expertise here, but I suspect that you would be
limited by bus, or disk, IO capability, since each stream would be
recording to disk as different files.

There is a setting like "HD Ring Buffer" or some such which I had to set
to a large number
to avoid buffer overruns.  My disks are obviously a tad slow.

> Or, perhaps the card's ability to handle multiple streams?

I sorely doubt the tuner card itself will deliver anything more, or less
than a single
FULL TS multiplex.  It is always up to the software to strip out the
PIDs which are
needed for any particular recording.