Output aspect ratio depends on input aspect ratio

[FieserKiller]

There is a bug in line 74 of the code which calculates outX wrong for input files with an aspect ratio != 4:3. I noticed because my video was 5:4 and the output file was not 16:9.
Fix for converting all input files to 16:9 is quite trivial tho, simply calculate outX from input height * desired ratio:
outX := int(float64(specs.Streams[0].Height) * (16.0 / 9.0)) / 2 * 2 // multiplier of 2

[Niek]

Thanks for reporting and providing the fix @FieserKiller! Fixed in 2689c70