add test for input h/w

[mcampos-quinn]

If one (or both?) of the input dimensions is odd, the libx264 (w/ yuv420p colorspace) access file transcode will fail (though it does produce a 0-byte file, annoyingly).

Add a test to read the dimensions of the input and if any dimension is odd, add a pad of 1 pixel to the access file (this is under discussion now with film collection staff as to the best approach....).

Here's a filter to accomplish this, scrounged from somewhere on StackExchange:
-vf pad='width=ceil(iw/2)*2:height=ceil(ih/2)*2'

This divides the input dimensions by two, multiplies by two, then rounds up to the next highest integer. I think we'll want to add x/y offsets to specify the pad on the left/right or top/bottom.