Q about fastest display methode

Glynn Clements glynn at gclements.plus.com
Tue Sep 16 06:27:49 PDT 2008

Aleksandar Lazic wrote:

> > Xvideo (Xv) extension covers 2, 3 and 4. This allows the use of a video
> > overlay if the hardware supports it, or the use of the GPU for scaling
> > and/or colour-space conversion as a fallback.
> should I use xv direct or the OpenGL Framebuffer Object or both and
> decide at runtime?

Xv is the preferred method for displaying video. Other mechanisms may
be useful as fallbacks if the server doesn't support Xv (for cards
which lack a video overlay, the driver will often still provide Xv
support via the textured video), or if the Xv support is broken.

> >This provides a substantial performance gain over converting to RGB and
> >rescaling in software. It may also provide better quality (cards which
> >provide a video overlay often have a rescaling filter which is much
> >better than anything that would be feasible in software).
> How about the new cards which are desigend for DirectX10, does they
> offer such 2D Acceleration?

All modern cards provide features which can be used to accelerate
video. At a minimum, any modern card will support image rescaling. 
Also, even if the card doesn't directly support YUV (technically
YCbCr) images, you can usually still perform the conversion by
rendering colourised versions of the individual channels in additive

By "modern", I mean anything that's still sold and almost anything
that's been sold in the last five years.

> >> 6.) I think I don't need the 3D functions of the cards.
> >
> >Video players often provide the option to use OpenGL for video display,
> >in cases where the X server supports GLX but not Xv (or in case Xv
> >support is broken).
> Due the fact that I'am not uptodate, what is the 'best' solution for the
> Mainstream cards at that time?

First, support Xv. Support for other rendering mechanisms depends upon
how important you consider fallbacks to be.

Glynn Clements <glynn at gclements.plus.com>

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