[mythtv-users] How to minimize CPU usage

Steven Adeff adeffs.mythtv at gmail.com
Sat Feb 4 17:33:29 UTC 2006


On 2/4/06, Kevin Kuphal <kuphal at dls.net> wrote:
> Steven Adeff wrote:
> > On 2/4/06, Kevin Kuphal <kuphal at dls.net> wrote:
> >
> >> Jerry Rubinow wrote:
> >>
> >>> On 1/30/06, Boleslaw Ciesielski <bolek-mythtv at curl.com> wrote:
> >>>
> >>>
> >>>> Jerry Rubinow wrote:
> >>>>
> >>>>
> >>>>> PVRs have existed for a while, but not HD-resolution PVRs - they're
> >>>>> pretty recent.  If X is in a 24-bit depth mode, then I don't see where
> >>>>> my numbers are off - 24 (bit depth) * 1280 * 720 (screen res) * 30
> >>>>> (fps) = 630+ Mbits/sec.
> >>>>>
> >>>>>
> >>>> 720p is (usually) 60fps.
> >>>>
> >>>> Bolek
> >>>>
> >>>>
> >>> That's what I thought, but that would mean 24 * 1280 * 720 * 60 = 1260
> >>> Mbits/second going to the video card.  There'd be no way that would
> >>> work over PCI - it'd be dropping every other frame (not to mention
> >>> that X reports 32 bpp, so 24 seems low), but it seemd like there was
> >>> much less dropage than that.  So there's something I'm not accounting
> >>> for, but I don't know what (this is without XvMC).
> >>>
> >>>
> >>>
> >> But here's something.  If PCI HDTV tuners can write the data just fine
> >> to the disk, how is it that much harder for the video card to push that
> >> much data along the bus as well?  Assuming XvMC takes care of the CPU
> >> load, even if the data on the bus is the same, a PCI video card should
> >> be able to handle as much as a PCI HDTV tuner can...
> >>
> >> Kevin
> >>
> >
> > DVB cards send an mpeg stream through the PCI bus, the data being sent
> > from the cpu to the  video card is "raw uncompressed" video
> > information.
> >
> >
> So I guess the question still remains, does XvMC make a difference in
> this case...
>
> Kevin



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