Resize is a YV12 port of Avisynth resize filter.
MPlayer resize is a port of Michael Niedermayer resize filter, which is used in MPlayer.
Avisynth resize is slightly more accurate, but MPlayer resize is 3x(nbsp)faster without any perceptible difference.
The filter dialog config box is the same for both filters. You can direcly enter the new width/height and the resize algorithm or use the slider and the menu.
In case you enter the values manually, press OK, not Apply, as pressing Apply recomputes the value from the slider position.
Three resize methods are proposed:
Remember: Sharp pictures look nice in preview, but they can cause problems when the video is encoded (especially at low bitrates). So don't rely on the preview only. Encode a short sample and check the encoded video!
The aspect ratio is very important for proper resizing. If the source is MPEG-1/2, you can be almost sure that the source aspect ratio is 4:3 or 16:9. AVI files are most commonly 1:1.
So to resize properly a widescreen DVD for example to MPEG-4 AVI (e.g. encoded with Xvid), select 16:9 for source and 1:1 for destination.
The framerate is also important. 4:3 MPEG has non square pixels, different for PAL and NTSC. So if you resize before altering the framerate you will end up with a differently sized image.
The 16 round up checkbox, when checked, will round up the resize value to the closest multiple of 16.