[mythtv] Aspect ratios and non-linear stretching

[Sean McVeigh]

Hi,
New to the list, fairly new to MythTV.  I'm looking to add support for a 
non-linear 4:3 --> 16:9 stretch mode to the display code, and am just 
fishing for opinions. 
(this is the sort of mode supported by some HDTV sets whereby the 
scaling ratio is 1.0 at the center of the screen, but as you approach 
the left and right extremes, a scaling factor > 1.0 slowly kicks in.  I 
almost always use this viewing mode when watching 4:3 content on my 16:9 
set -- but sadly it is only supported for SD inputs).
It's my understanding from a quick skim through the code that display 
aspect ratios (the W-key stuff) are just handled by altering the 
geometry passed to the X blitter.  Short of writing a new X-blitter, or 
a filter plugin, it would seem that a reasonable approach would be to 
hook in somewhere before Show(), ie. ProcessFrame() and generate frames 
with a new geometry.
I'd rather not explicitly do it as a filter, since it's my understanding 
that filters can't be arbitrarily enabled and disabled at runtime with 
the press of a button.  (if that's not the case, please let me know).  
Also, I am unsure as to whether filters work with frame images in-place 
or can return new frames with new geometries.. haven't read that far 
into things.

Anyhow... opinions on the cleanest approach, maintainability and 
useability-wise would be appreciated :)

Cheers,
Sean