Megui Resize Filter

[xxxThiefxxx]

Can someone explain me what do each option and which one you think is best?
Bilinear(Soft)
Bicubic(Sharp)
Bicubic(Neutral)
Bicubic(Soft)
Lanczos(Sharp)
Lanczos4(Sharp)
Gauss(Neutral)
Point(Sharp)
Spline16(Neutral)
Spline36(Neutral)
Spline64(Sharp)

[Selur]

depends on what your goal is, here are some comparisons that might be interesstring:
http://hermidownloads.craqstar.de/videoresizefiltercomparasion/
jeanbruenn.info/2011/10/30/upscaling-in-avisynth-comparison-of-resizers

personally I prefer Bicubic(Neutral) for downsizing,..

[xxxThiefxxx]

I have one hdtv video 1080p 8GB and i want to make it around 800MB 720p... So what is your suggestion for this?

[Selur]

1. you are downsizing, so I would use&recommend Bicubic(Normal) as resizer
2. I would also strongly recommend to aim for a higher file size since 800MB for 720p (1280x720 progressive) is just not enough for most content to look decent. It is probably doable for anime content or if the bit-rate the of the 1080p content really was way higher than needed or the format the content was saved in wasn't really compressed that much.

[hello_hello]

I agree regarding the file size. x264 is very good at compressing video quite a bit, but 800MB is well into looking pretty average territory for a 720p video (assuming it's movie length).

As a trial, try encoding the video using single pass CRF encoding and a CRF value of 20. The file size will be whatever it needs to be, but it'll give you a rough indication as to how much you can shrink the video without it taking too much of a quality hit. Most people encode using CRF values between 18 and 22 (the lower the CRF value the better the quality and the larger the file size).

Given your resizer list, would it be safe to assume you're using MeGUI? If so, while you're setting up an encode using the Script Creator you can select the "Preview AVS Script" button at the bottom of the window. If each time you make a change to the script you hit that button again, the preview window will give you a preview of the changes.
Using the above method you can change resizers and preview each one to look at the differences. Maybe select a frame of video with a reasonable amount of fine detail while you're comparing the resizers. As some of them are fairly similar you mightn't really see any difference at all, especially if the source video isn't particularly sharp to begin with. I mostly use Spline36 but it's all personal preference. If you're really wanting to compress the video down to a small size I think it'd probably pay to use softer resizer.

For instance if you run two identical CRF 20 encodes (same x264 settings) and the only thing you change is the resizer you use each time, you'll see how much each resizer can effect the final output size.