[mythtv-users] Number of virtual tuners

[Michael T. Dean]

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".  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.

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

Mike