[mythtv-users] How to minimize CPU usage

[Jerry Rubinow]

On 2/4/06, Kevin Kuphal <kuphal at dls.net> wrote:
> Jerry Rubinow wrote:
> > I would think that the GPU on the video card is being used for the
> > heavy lifting of decompression, as you say.  But is the buffer holding
> > the output of those calculations on the video card or system RAM?  And
> > if it is on the video card, does it have to travel back to the system
> > first before being sent to the video card's output buffer, or does it
> > go directly there without traveling back and forth over the bus first?
> >
> > I would guess for the first question that the GPU only operates on
> > memory on the video card.  For the second question, it depends on how
> > sophisticated the code is and the algorithm.
> It seems to me after thinking about it that it has to go:
>
> HDTV caputre (MPEG-2) -> disk (MPEG-2) -> MythTV (MPEG-2) -> XvMC
> libraries (MPEG-2) -> hardware GPU (MPEG-2) to video buffer (raw)
>
> It would seem illogical that anywhere in the chain are the MPEG-2 frames
> decoded by the application or the libraries because XvMC offloads this
> decoding to the GPU.
>
> In that case, the load on the PCI bus from disk to card should be the
> same as from capture card to disk and we within the specifications of PCI.
>
> Kevin

I agree, that's the logical way to do it.  But I don't know enough
about how it works to know this for sure.  Hopefully someone who knows
about the internals of this will reply with a brief primer.