[mythtv-users] DVB(S) tuner sensitivity (and my other) experiences

[Robert]

Dave wrote:
>  > Swapping slots isn't an option as both PCI slots are used and the
>  > graphics card is AGP.  And yes, the Quadro is only supported by the
>  > legacy NVidia drivers, but the version number isn't that far behind
>  > the latest drivers.  (The card was given to me which is why I'm using 
> it!)
> 
> That's the issue with SFF pc's. Lack of space to juggle cards around. I 
> wish in hindsight i'd gone for a bigger media htpc case.

Indeed.  I would certainly buy a "larger" case next time, to have room 
for capture cards, etc, but since I got the offer of a P4-2.66 in a 
fairly quiet SFF case for £30 I thought it was worth a shot for my first 
  mythbox :-)

> 
>  >> I have, CPU usage is generally low (10%) when recording DVB-S and
>  >> doesn't max out at any point.
>  >>
>  > How do you check interrupt usage with vmstat?  Is this just the IO
>  > column?
> 
> No the 'in' column (as in 'interrupts') from vmstat.

Ah, of course.  It seems to be usually around 1400 during recording / 
playback and I've not see it go much above that.  I don't know if this 
is good or bad!

> When you have the nv/agpgart driver loaded as oposed to the nvidia i'm 
> sure it's not on the same IRQ 16 as your DVB card is it?

Indeed.  The nv driver doesn't seem to use any interrupts as far as I 
can tell.

I've tried noapic and irqpoll, but neither fix the problem.  noapic 
seems to make it a little better, but that could just be subjective.

The annoying thing is that one of my DVB-S channels doesn't have this 
problem at all under linux.  And they all work fine when I use Windows 
on the same box.  Also my STB which is connected to the same feed from 
the sat dish works flawlessly on all channels.


I think I might look into getting a new graphics card and see if that 
helps matters, but I keep thinking if it works under Windows then why 
not under Linux?

Robert.