Tests were done and found that Intel IPP filters (vsoscaler.dll) weren’t that good and bugs were reported to Intel but they don’t seem interested to fix it, so VSO has decided to rewrite the resize filters from scratch. If you did a clean install, the installation script no longer has vsocaler.dll (or swscale.dll - old FFMPEG scaler) in it. If you still find it in the CXD installation folder, just rename it to something else or remove it, or do a cleanvso and reinstall. The new scaler is now internal to the program, no DLL is used.
There are numerous filters available but are not exposed until v4 release. The 3 interested filters are fast linear (top speed), linear (compromise between speed and quality), and lanczos (quality). I think it’s either fast linear or linear is the default, but linear is already pretty good.
The 2-pass option will be exposed in v4. I’ve done some tests but find only slight quality gain in 2-pass over 1-pass, except that it will be slower for 2-pass. However, if you enable multicore support, it’ll be pretty quick.