Resizing Suggestions

[kandiman]

Hi all,

i have a quick question about resizing, i usually capture in avi uncompressed format 704x576 and resize the video in vdub to 640x480 and select precise bilinear then encode the file to mpeg2 in tmpg ....

with my resizing method in vdub do i lose any quality doing it my way?, or is there a better way to resize?

any help will be nice

[Baldrick]

yes, you will lose quality or more like video information when you downsize and then convert again. why not convert directly to mpeg2 with tmpgenc??? and if you are making dvd you are upresizing = BAD . tmpgenc can resize if you want to make 640x480 or use the virtualdub frameserver, www.videohelp.com/virtualdubframeserve

[kandiman]

hi thx for the reply....i do not wish to make a dvd...its purely for pc playback, the reason i resize is i need to crop the video so i thougt i might as well resize too..

i thought i was downsizing from 704x576 to 640x480 = good ...heheh

[Baldrick]

downsizing once is good. but downsizing and then encode again not good(well if you convert to uncompressed avi with virtualdub you wont lose quality). use the virtualdub frameserver and you can do everything in one step, www.videohelp.com/virtualdubframeserve

[kandiman]

aaaaah many thx i neva tried frameserving bfore i will give it a try

one more thing....i dnt get wat bilinear, precise bilinear means....like which is the best one too use

[Suntan]

There is no best.... (sorry, but you will get that answer a lot.)

They are just different algorithms used to resize. In general it is assumed that quality goes from worst to best (read: blurriest to sharpest) like this:

nearest neigbhor, bilinear, bicubic, lanczos. (Vdub doesn't have lanczos afaik, you will need to learn AVIsynth for that.)

Note, they also go from quickest to slowest this way.

Arguments can be had (and are had) that adjusting coeffect values for bicubic (or precise bicubic) will give sharper resize than lanczos, but that is up to you to decide when you have the time to test for yourself.

To keep it simple, don't use nearest neigbhor. Use bilinear if you are downsizing and you want a slightly softer (more compressable) image, use bicubic if you want the most sharpness.

Most important, try them all and use the one you like the best.

Also important, for best quality PC playback don't resize at all. Just crop the black bars and resize/AR correct at playback (with a media player like zoomplayer.)

-Suntan

[BSR]

downsizing once is good. but downsizing and then encode again not good

Not sure if I understand?

So if I wanted to encode to say DV to 352x480 for DVD.
You are saying it is not good to crop(704x480) and resize(352x480) in Avisynth and then encode with TMPGEnc,
but to crop in TMPGEnc and encode right to 352x480 from the higher resolution?