[MPlayer-users] Re: Changing aspect ratio while playing a file

[Sebastian Kaps]

Hi Rich!

>> [xvidix] window properties: pos: 625x492, size: 264x264
> OK, this is a bug. It's supposed to (and last I checked it did) scale
> to 625x625. 

625 is only the x-coordinate of the window position, not the horizontal
window size. 264x264 is the value you should look at.
The video originally has a resolution of 352x240 (I currently have no
better test candidate). And these 352-264=88 pixels are gone.

I checked with another video, having a resolution of 480x480. Now this
one is scaled to 640x480 first and then to 480x480 for display.

So it seems videos are scaled to 4:3 ratio and then the result is taken
and scaled for 16:9 screens.
If I understand it correctly then you gain quality for videos where the
x-resolution is smaller than 4/3 of the y-resolution since the
x-resolution is upscaled to fit that ratio and then the scaling for 16:9
screens is done.
You lose quality if the x-resolution is larger than 4/3 of the
y-resolution, because the y-resolution is scaled up to fit in 4:3 and
then the x-resolution is scaled down for 16:9.

> Anyway you're not playing video in a window for TVout, you're playing
> it fullscreen, and in that case there is no downscaling!

That doesn't matter since I assume having a video in TV resolution
(720x576) being played on a screen with the same resolution. Fullscreen
and windowed mode should then only differ in the the window manager's
window decorations. For videos with lower resolutions we don't need to
talk about quality loss.

-- 
Ciao, Sebastian