Quick Resizing Question

[Master Yoda]

If i wanna resize something from 720 x 576 to 352 x 576 ,can i just use this line in my avs ..

BicubicResize(352,576)

As BicubicResize was what i used when i used to do svcds.

[scharfis_brain]

this will deliver a slightly wrong Aspect Ratio

704 Pixel width corresponds with 352 Pixel width.

because of this, you have to crop 8 Pixels left and right before resizing, like this:

crop(8,0,-8,0).bicubicresize(352,576)

[Master Yoda]

So i put this

crop(8,0,-8,0).bicubicresize(352,576)

all on the same line. OK

[scharfis_brain]

If the dot between both commands is confusing you, you can use another notation:
crop(8,0,-8,0).bicubicresize(352,576)orcrop(8,0,-8,0)
bicubicresize(352,576)orbicubicresize(crop(8,0,-8,0),352,576)orbicubicresize(352,576,0,0.75,8,0,-8,0)Take a look in the AVIsynth manual for more details.

[N_F]

How does VerticalReduceBy2() compare to bicubicresize(352,576) in this case?

[scharfis_brain]

verticalreduceby2 gives you 720x288 pixels

take horizontalreduceby2 instead. it results in 360x288 (EDIT!!! it has to be 360x576) Pixel. then crop 4 Pixels left & Right. The result is IMO the same like bicubicresize.

horizontalreduceby2().crop(4,0,-4,0)

EDIT: the AVIsynth doc says, it is good for compression, hehe

[N_F]

Sorry, I meant HorizontalReduceBy2() :o

[Jellygoose]

Could you actually use the ReduceByX() call to resize to VCD resolution? Would it give you a better compression in some way?

[lpn1160]

Hope this stays on topic,
I capture @ 480x480. I resize for DVD (I use # Lanczosresize(704,480)
do I need to crop??
Is there a formula to follow for resizing to different resolutions??
Everything always looks fine, whats the deal??

Thanxs in advance

[r6d2]

Originally posted by lpn1160
Is there a formula to follow for resizing to different resolutions??
Try this (http://www.uwasa.fi/~f76998/video/conversion/) guide. It contains an algorythm.
Everything always looks fine, whats the deal??
If the AR error is below 2%, it is likely you will not notice it.

[Boulder]

You can also use FitCD to determine the correct cropping and resizing and possible aspect ratio error.

[r6d2]

Originally posted by Boulder
You can also use FitCD to determine the correct cropping and resizing and possible aspect ratio error.
Very good idea, FitCD implements exactly the algorythm explained on the guide I quoted, but hides it to the uninitiated :)