[MEncoder-users] video filter scale (n+8)

[Jon Drukman]

i'm trying to set the scale to 640 wide and nearest multiple of 16 high 
(for H.264 encoding of arbitary sized input files).  the documentation says:

scale[=w:h[:interlaced[:chr_drop[:param[:param2[:presize[:noup]]]]]]]
	
0: scaled d_width/d_height
-1: original width/height
-2: Calculate w/h using the other dimension and the prescaled aspect ratio.
-3: Calculate w/h using the other dimension and the original aspect ratio.
-(n+8): Like -n above, but rounding the dimension to the closest 
multiple of 16.


i want the -3 option but with the rounding.  i've tried -vf scale=-3+8, 
-vf scale='-(3+8)' but it always gives an error

The w option must be an integer: -3+8
Option vf: Error while parsing scale parameter w (-3+8)

i'm using the latest SVN as of yesterday afternoon.  what's the correct 
syntax?

-jsd-