bicubic resize help 4 PAL users

[uk_dan2k]

hi, im converting an avi to dvd, normally i skip dooms part on using the avi script and go straight to tmpgenc, but want to try it now and see if it makes a difference.

Its in ntsc the guide but works the same for pal and was wondering if these calculations are correct.

my video source =544x304
source aspect ration = 1.789 which is nearest too 1:1.85.
I want a PAL DVD = 720x576, which means playback res = 768x576.

I need to stretch the film to 768, 768 / 544 = 1.4117 resize ratio, so 304 x 1.4117 = 429.1568 = nearest even number = 430.

so the avi should end up 768x430 and then just add some black bars = 576 - 430 = 146 / 2 = 73 = 72, 74

so the script should look something like this: -

AviSource("c:\movies\somemovie.avi")
BicubicResize(768,430,0,0.5)
AddBorders(0, 72, 0, 74)

thanks for any help, sorry for the newb question.

[wonkey_monkey]

When encoding for DVD, you want a video size of 720x576 - the pixels aren't square.

Additionally, with an input size of 544x304, you could take advantage of anamorphic video. A quick-and-dirty approach would be to resize straight to 720x576 and encode it - the difference between doing that and calculating the proper numbers will only be a few pixels - not enough to lose sleep over ;)

My back-of-a-bit-of-paper calculations suggest that for a mathematically correct (non-anamorphic) resize, you should resize to 720,439 and add borders. For an anamorphic picture, resize to 732,576 and crop 8 pixels from either side. I could be wrong about this though, so I won't bore with possibly incorrect maths.

David

[uk_dan2k]

When encoding for DVD, you want a video size of 720x576 - the pixels aren't square.

Additionally, with an input size of 544x304, you could take advantage of anamorphic video. A quick-and-dirty approach would be to resize straight to 720x576 and encode it - the difference between doing that and calculating the proper numbers will only be a few pixels - not enough to lose sleep over ;)

My back-of-a-bit-of-paper calculations suggest that for a mathematically correct (non-anamorphic) resize, you should resize to 720,439 and add borders. For an anamorphic picture, resize to 732,576 and crop 8 pixels from either side. I could be wrong about this though, so I won't bore with possibly incorrect maths.

David

maybe a dumb question but how did you get those sizes and when and why is croping used?

thanks.

[wonkey_monkey]

This is only my current understanding and may be incorrect...

In the 720x576 picture, the actual area that is, according to the specs, to be viewed at a 4:3 ratio is 704 pixels wide - that is to say, when played back by a computer, the central 704x576 "column" should be stretched out to 768x576 (a 4:3 frame) (The extra 16 pixels are there as a buffer from the days when converting from analogue to digital was a bit dodgy).

The enclosing picture, though, is 720 pixels wide. When pulled out by the same ratio (768/704), that becomes 785.4545r pixels wide. So you want (mathematically) to scale your picture in both dimensions to that width before squeezing it down (because DVD pixels aren't square) to 720 pixels wide. (785.4545r/544)*304=439, or thereabouts, so that's your target height.

I think I was mistaken about those anamorphic numbers - I now think you should resize to 708x576 and add 6 pixels to the left and right. Just at the moment I can't think how to explain why in plain English...

To be honest, if it was me, I'd ignore all of this and resize either to 720x432 (a nice non-anamorphic size) or 720x576 (anamorphic) - the difference in aspect will be negligible.

David

[Master Yoda]

Just a quick suggestion, try FitCD that calculates it for you and gives you the resize numbers. This is what i use, seems to work fine so far.

[uk_dan2k]

I didnt know about the 704 pixels instead of 720, i thought u just used 720 all the time. Still a little confused about (785.4545r/544), but after checking out FitCD i noticed the resize number are very similar to yours dave. After not touching hardly any settings apart from no cropping and selecting DVD 704 it came up with
704x432

looks like yodas tools gives less headache lol, thanks for the help guys.