[MPlayer-users] Null video filter?

[Baxter Kylie]

Hi.

I'm in a bit of a bind. I need some sort of null video filter.

I'm trying to put together a wrapper for mplayer so that I can utilize
true dynamic fullscreen software scaling (eg, display 1280x720 -- if
content AR < display AR scale=-3:720, elseif content AR > display AR
scale=1280:-3).

Now, most of the work is done. I grab the display stats with xdpyinfo,
and the content stats via midentify, and mix it all together into a
happy little command line string. Because I don't want to replace the
mplayer config structure altogether I'm using profiles as optional
arguments in the wrapper and only passing those, the content location,
and the scale argument.

Since scaling is usually the last step in a filter chain it works out
nicely to pass the scale arg as -vf-add scale=x:y

The difficultly, of course, is that not all of my profiles need or use
other filters in the chain and -vf-add crashes out if there is no
video filter chain already active. A null filter would be most ideal
(that or a change to the default behaviour of -vf-add) but since
neither of those exist, can a fake null filter be created?

I'm not familiar enough with the deep inner workings of filters to
know but, if a video filter is initialized and passed arguments that
basically tell it to do nothing (think scale=0:0), does it still use
system resources or negatively impact quality? If not.. is there a
filter you'd recommend as being ideal for this application?

Best and thanks.
~BK