Current guide to x264 "--vf" downscaling modes

[benwaggoner]

I'm playing around with the internal x264 scaling modes from libswscale. I'm having a devil of a time finding useful documentation about them. The most definitive I've found is this one, but the actual research was done in 2008!

http://forum.doom9.org/showthread.php?t=160593

The default of bicubic is good for moderate downscaling almost everywhere. But I'm trying to figure out what's the most neutral one for big ratios (like 1920x1080 to 352x192); that's >5x. And with 4K sources starting to be used, we'll have >10x ratios for some scenarios. For this kind of stuff, even bicubic has historically had trouble with the fine details of rolling credits and that sort of thing. Heck, and optimal scaling algorithm has as many taps as the source frame has pixels that overlap with the region that the output pixel comes from, so that'd be 25+ even in the 1080p -> 192p case.