Resizing. Bilinear or bicubic actually?

[Enchanter]

Okay. I know from guides and a few others that when shrinking a video (from 720x480 to 480x360, with cropping as well), we should use bilinear. However, I have also read that if you don't use bicubic, the result is a rather blurred video.

I am currently encoding an animation movie. The result is good with bilinear, but somehow it looks even sharper with bicubic. Can you all give me your comments on this? I wonder if this is just me or if bicubic really shouldn't be used for shrinking videos.

[benderman]

Bilinear is for shrinking, bicubic is for enlarging. Maybe bicubic also works well for shrinking, but the smoothing effect of the bilinear resizing is perfect for divX-compression. Smooth video is compressed better and with less artifacts.

[Enchanter]

So would you say that, if I used bicubic and hence get less smoothing, I would end up with a file that is bigger than if I used bilinear? Or will the resultant file be more difficult to play with (ie. requires more CPU power)?

[benderman]

Smoother video will reduce sharp edges and so the video can be compressed better. Better means smaller filesize and/or smoother playback with less details. The effect is minimal, if you want to experiment use a smoothing-filter like in VirtualDUB.

[UncasMS]

two more things to keep in mind:

1. if you resize only ONE side (height or width) bilinear is fine.
for resizing both, x and y better use bicubic.

2. bilinear smoothes und thus blurs your picture. if you want best sharpness: again use bicubic!

[Enchanter]

Thanks for the input.

One last question though. How much more CPU power will be required to run a file resized by bicubic, compared to that by bilinear? Is it near negligible?

[benderman]

@UncasMS: I can't agree with you. Every resizing-filter works better if you only resize one side, no matter if bicubic or bilinear. The only difference is that bicubic uses an algorithm that produces sharper edges so that it is much better for enlarging pictures. If you shrink a picture bilinear is the better choice, simply because it is faster and produces nearly the same result.

[can2day]

I switched from using bicubic to bilinear filtering in Flask and the rips I have made since do look noticably blurrier. Eventually, I switched back to bicubic.

IMHO, if you're going for quality, stick with bicubic. That said, my rips always came in undersize by about 10-20% of what I had calculated.

[UncasMS]

since this thread is more than 13 month old and things have changed a little, my one and only resizer for month now is:

LANCZOS

excellent sharpness and still less visible artefacts than sharp bicubic

[Enchanter]

This is one old thread I never expected to see again!

That said, I am with Uncas in preferring lanczos over any other types of resizers.

[UncasMS]

This is one old thread I never expected to see again!

true

i came across this old thread by accident

[t3ch]

rofl....

I was like what the hell...