[MPlayer-dev-eng] gl & distorted fisheye for dome projection

[Johannes Gajdosik]

On 06/28/2006 03:27:39 AM, Rich Felker wrote:
> As much as GL might be able to accelerate this, filtering features
> really do not belong in the VO driver but rather as vf modules. Could
> you write a vf module that would support this with any video out?

Yes, it would of course be possible, but it would be difficult and I do
not expect much more than 2 frames/second without hardware acceleration.

> Performance may suffer somewhat but I assume that users with such
> exotic equipment will have sufficiently powerful machines to handle it

You misjudge the situation. They usually build their domes by themselves,
sometimes with cardboard and foam, or in other interesting ways.
It must work and it must be cheap. A computer with opengl graphic card
is not expensive any more. The only things they have to buy is the
security mirror and the projector. Once I even got a 'thank you'
from a teacher in some south-american country, who is now able to
build a planetarium on his own.

> and it's certainly much cleaner to implement as a filter than as a
> hack in the VO driver.

Certainly. Yet I see no way how to get realtime without openGl.

On 06/28/2006 03:52:22 AM, Robert Henney wrote:
> So, rather than implement this within a gl* vo, couldn't the spherical
> texture be created by an external program and the handle for that
> texture then get passed to the gl vo (via mplayer command line) to use
> in place of the one the gl vo would create on its own?  that seems like
> a much more general approach to using/extending the functionality of the
> gl vo that could accomplish what you're looking for.

The texture contains the image data of the current video frame.
The gl vo somehow manages this, I did not yet investigate how it is done,
because it is irrelevant for my purpose.

And then this texture is mapped onto the screen. Currently there is
only a very simple mapping in gl vo: just linear scaling.
But using OpenGl you have an unlimited variety of possible
image distortions by specifying how the mapping shall be performed.
And it costs nearly nothing, because it is done in hardware.

Johannes