[mythtv-users] How to minimize CPU usage

[Jerry Rubinow]

On 2/10/06, Kevin Kuphal <kuphal at dls.net> wrote:
> Bob 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.
> >>>
> >> 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).
> >>
> >
> > Just to confuse matters, I'm pretty sure I've driven my CRT at
> > 1600x1200 at 100hz from one of my PCI graphics cards, (CRTs been in storage
> > for 7 months, should get it back in a week so can check) this means that
> > under X the whole raw frame doesn't get shoved from the CPU to the GPU
> > across the bus, I think this is the difference between the frame buffer
> > and a hardware accelerated 2D environment like X.
> >
> I'd have to agree with this.  The specs of the cards say they do upwards
> of 1920x1088 or more.  It would seem illogical for a card to purport a
> specified resolution and not be able to deliver it.  I will probably be
> getting a PCI MX4000 in the next few weeks for my system and I will
> report back my results with HDTV playback to an SD TV.
>
> Kevin

But isn't it one thing to be able to process a bunch of OpenGL vertex
lists and other graphics primitives making up the objects and
construct a 1920x1088 frame from them on the video card, and quite
another to pump the full pixel data for the frame to the card
yourself?

In other words, just because you can give the card four coordinates
and have it draw a 1920x1088 rectangle on the screen doesn't mean the
bus has the bandwidth to give it every single pixel of that rectangle
at video rate.

-Jerry