[mythtv-users] XvMC question

Scott Kidder kidder.scott at gmail.com
Tue Jul 29 06:18:14 UTC 2008

Using XvMC made for an interesting challenge: why do something in software
when it can done much more efficiently in hardware.  Yes, I see about 80%
CPU usage when playing 1080i content.  But power consumption is also
significantly higher for the machine: around 160 watts, compared to 110
watts when using XvMC.  This is a non-trivial issue for an appliance that's
powered all day (although it's not playing 1080i content all day).  Also,
lowering the load on the machine introduces the possibility of running some
other services on the machine so that it isn't strictly a MythTV box.  With
a higher load, it's questionable whether I can run those other services
without compromising the frontend performance.  Lastly, a higher CPU load
makes for more heat that must be expelled from the case before it impacts
the longeivity and reliability of the other components.

I noticed that you have separate frontend & backend machines.  I'm using a
single machine for frontend and backend.  Playback of 1080i content get
murdered when commercial flagging begins.  This was never the case when
using XvMC.  And, yes, I lowered the priority of the commericial flagging to
19 with nice, yet it's still an issue.

Scott Kidder

On Mon, Jul 28, 2008 at 8:20 PM, Yeechang Lee <ylee at pobox.com> wrote:

> Scott Kidder <kidder.scott at gmail.com> says:
> > I, too, was having problems with audio stuttering during ATSC
> > playback using XvMC on both an NVidia 5200 FX and 6200.
> [...]
> > There's a higher load placed on the CPU (P4 3.0 GHz Hyper-threaded),
> > but it's only around 70% of an otherwise idle machine.
> Why are you using XvMC in the first place? A 3.0GHz Pentium 4, with or
> without Hyperthreading, and an Nvidia 5200 or 6200 should be fast
> enough to be able to play 1080i recordings at about 50-70% CPU usage
> without XvMC, assuming there's nothing intensive else the computer is
> doing. Yes, slightly lower CPU usage than with XvMC.
> --
> Frontend:               P4 3.0GHz, 1.5TB software RAID 5 array
> Backend:                Quad-core Xeon 1.6GHz, 6.6TB sw RAID 6
> Video inputs:           Four high-definition over FireWire/OTA
> Accessories:            47" 1080p LCD, 5.1 digital, and MX-600
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