[mythtv-users] Number of virtual tuners

[Tapani Tarvainen]

On Thu, Apr 26, 2012 at 09:38:50PM -0400, Michael T. Dean (mtdean at thirdcontact.com) wrote:

> On 04/26/2012 03:19 AM, Andre wrote:

> > When multirec was being developed 5 was decided on as the point
> > where performance was still good on contemporary hardware.

> More precisely, 5 was determined to be the "sweet spot".  Each
> additional virtual tuner you add increases resources required to
> schedule by a greater and greater amount (non-linear increase),

Do you have a more specific idea which particular resources
we are talking about here?
CPU power, RAM, disk I/O, what?

> and the resource increase for the first 5 was reasonable compared to the
> benefit they provide, but the 6th virtual tuner required a huge
> increase in resources (and additionals even huger) for very little
> gain.

Presumably that would only happen if you actually configure
more virtual tuners per card, so merely increasing the limit
one _can_ do would have no impact on people who don't need it.

I agree that _default_ should be set to something that works
well on average hardware, but maximums, hard limits, should
be generally something like "biggest that might make sense"
and let people find their own sweet spots.

In any case, hardware has become rather more powerful since the
limit was set. Perhaps 5 was indeed biggest reasonable value
then, but if someone is already using 8 with success,
it would seem it's time to reconsider the limit.

> (Especially when you can pick up additional cards for cheap.)

The only DVB-C cards I've found that actually work here
are all fairly expensive PCI ones, and I have no free PCI
slots left in my mythtv box or indeed room in the case,
so I'd have to replace the motherboard and chassis,
or build a separate slave backend...
Getting faster disks or more RAM or even a faster CPU
would be easier and cheaper.

Fortunately it is indeed free software and recompiling
from sources is not too hard.

-- 
Tapani Tarvainen