Avisynth: Bilinear or Bicubic?

Adder · #1 01-07-2005, 02:24 AM

i know if your upsizing a movie to use bicubic and if your down sizing res to use bilinear what about if you have done a dvd backup and use the same res as source i.e. 720x480?

thanks.

incredible · #2 01-07-2005, 04:03 AM

Quote:

Originally Posted by Adder

i know if your upsizing a movie to use bicubic and if your down sizing res to use bilinear

Who says that?

Quote:

what about if you have done a dvd backup and use the same res as source i.e. 720x480?

? Same resolution as source means NO resizing, so which algorhythm in this case is not an issue.

We only do crop from 720x480 to 704x480 as 720 for TV purposes make NO sense.

We avoid upsizing as the upsizer would do the same trashy output as the SAP would do by itself when feeding with lower resolutions.
The only way for upsizing is the function of didée of doom9 called ipp which does a LOT of image enhancing but its SLOOOOW.

Also limitedsharpen() of didée does the best sharpen job for upsizing I know, but anyway .... where no details are, there want be any more details afterwards, just a subjective enhancement for your eyes, thats all.

Dialhot · #3 01-07-2005, 04:46 AM

Quote:

Originally Posted by incredible

Who says that?

Guess who...

"If you are magnifying your video, you will get much better-looking results with BicubicResize than with BilinearResize. However, if you are shrinking it, you are probably just as well off, or even better off, with BilinearResize."

file:///C:/Program%20Files/AviSynth%202.5/Docs/english/corefilters/resize.htm

It's not everyday we have a user that read the manual

Note: May I have to delete your first post ?

incredible · #4 01-07-2005, 05:34 AM

Seems to be an php error as I did ADD something and not delete

So why the larger post is above??

the viking · #5 01-07-2005, 06:28 AM

Dialhot wrote:

Quote:

It's not everyday we have a user that read the manual

OK,ill do it from now...

-----------------------
viking

muaddib · #6 01-11-2005, 11:47 PM

Quote:

Originally Posted by incredible

... as 720 for TV purposes make NO sense.

I understand what you mean... but I keep wondering:
If it makes NO sense, why the majority of DVDs comes with 720 and not 704?

incredible · #7 01-12-2005, 03:26 AM

Cause the industry by this follows D1 standard.

And in case of non analogue Signal (any other than TV) like beamer/projectors (pixel based) the 720 will be shown as progressive 720x540 (*imho*).

But Jukka Aho explains the 720 reason very well:
(Point 4.1)
http://www.uwasa.fi/~f76998/video/conversion/#faq

Quote:

4.1 Isn't 720 the real width of a 4:3 image? If not, then why are 720 pixels sampled instead of 711 or 702 (or whatever)?

720 pixels are sampled to allow for little deviation from the ideal timing values for blanking and active line lenght in analog signal. In practice, analog video signal - especially if coming from a wobbly home video tape recorder - can never be that precise in timing. It is useful to have a little headroom for digitizing all of the signal even if it is of a bit shoddy quality or otherwise non-standard.

720 pixels are also sampled to make it sure that the signal-to-be-digitized has had the time to slope back to blanking level at the both ends. (This is to avoid nasty overshooting or ringing effects, comparable to the clicks and pops you can hear at the start and end of an audio sample.)

Last but not least, 720 pixels are sampled because a common sampling rate (13.5 MHz) and amount of samples per line (720) makes it easier for the hardware manufactures to design multi-standard digital video equipment.

muaddib · #8 01-12-2005, 09:10 PM

Quote:

Originally Posted by incredible

Cause the industry by this follows D1 standard.

Yes, I know.
I would like to understand why...

Quote:

But Jukka Aho explains the 720 reason very well:
(Point 4.1)
http://www.uwasa.fi/~f76998/video/conversion/#faq

Ok Inc, thanks!
That makes (a little) "sense" to me...