[mythtv-users] Number of virtual tuners

[Andre]

On 27 Apr 2012, at 03:38, Michael T. Dean wrote:

> On 04/26/2012 03:19 AM, Andre wrote:
>> On 26 Apr 2012, at 05:00, Tapani Tarvainen wrote:
>>> On Wed, Apr 25, 2012 at 10:44:42PM +0200, Karl Dietz wrote:
>>> 
>>>> You can record overlapping programs from one DVB card with the multirec
>>>> feature. By default each DVB cards gets added as 2 virtual tuners.
>>>> You can push that up to 5 in mythtv-setup.
>>> Is there some reason to that limit, by the way?
>> 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".

I was going from memory :-) I followed that development with great interest, oh and contributed to the bounty.


>  Each additional virtual tuner you add increases resources required to schedule by a greater and greater amount (non-linear increase), 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.

Is there a difference in the resources required for 2 cards with 10 virtual tuners as against 4 cards with 5 virtual? I thought Myth didn't fully "understand" multirec virtual tuners and treated them the same as real ones for scheduling, not moaning, just curious.


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

Well yes, ish DVBS2 cards that actually work properly are still a little expensive >£80 but when adding an extra card requires hiring a £150 a day hoist to externally cable extra satellite feeds and replacing Motherboard to get extra slots, which then means new CPU, new ram! Of course MythTV has never been a budget solution and there's always the re-compile option. Would be nice to be able to stay on the binary builds though, how about storing the limit in the DB somewhere?

Andre