Ragga Muffin <[EMAIL PROTECTED]> writes:
> Aaron Solochek <[EMAIL PROTECTED]> wrote:
>
> > I was wondering what the difference between overlay and grabdisplay are,
> > in terms of preformance. I am running AcceleratedX 5, and I think that
> > means I can't do overlay. I have a g400max, and was wondering,
> > basically, what the optimal setup would be.
>
> In overlay mode the video is copied directly to the framebuffer, thus
> the need for cpu intervention is minimal.
> I'm not quite sure what grabdisplay is, but it seems to involve
> copying data from the bus to memory to display so it can be quite slow.
>
> Whether you can do overlay is, AFAIK, dependent on the videograbber board
> and not so much related to which Xserver you are running. (IIRC, AccelX
> worked fine here with a bt848 card and a Matrox G200).
>
> For xawtv, you need to run v4l-conf as root once to set things up for
> overlay.
Seems there's a confusion in the following mails between:
* grabdisplay: make a huge memcpy of each frame to the X server (only way
to play with export DISPLAY (hope you have a 100Mbps Ethernet network :-) )
Following are local only:
* overlay flavour 1: by some magic way, the card grabs directly to the
video ram and without cpu intervention, the image is refreshed (in RGB mode
I think). It must cause a slight performance loss though because the bandwidth
on PCI bus is not infinite (try putting four TV cards to see what happens).
[how does that thing scale???]
* overlay flavour 2: XvImages and friends; here the card grabs to a special
shared memory segment (can be in YUV format). The image is not converted
to RGB before sending to VGA, and is hardware scaled.
I can't see a valid reason to use this one (which requires a X4.0.1 setup)
compared to the previous.
* overlay flavour 3 (analog): the VGA card output is filtered by an analog
overlay that replaces a keycolor by an analogic signal.
--
Emmanuel Michon
Ing�nieur en d�veloppement logiciel
REALmagic France
Mobile: 0662834836 GPGkeyID: D2997E42
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