HELP - DAR (Display Aspect Ratio)

[Delta2]

Hi,

I'm new in doom9's forum, I don't know where to put my question.

I read the DAR (Display Aspect Ratio) guide, but I still have questions, so I need experienced help

1) AVI to DVD

Imagine I have a AVI source of 640x240 resolution

what calculations must I do in order to keep the aspect ratio on a DVD PAL compliance DVD with letterboxes ? in order the avoid squeezed and thin images ? or fat ones ?

i.e.

640x240 AVI source will result on 720x????? with XXX size letterboxes, what length should it be ?

2) DVD to AVI

in reverse, what resolution must I use to encode a DVD PAL (720x576) to DivX using FFMPEG tool ?

please, give me some explanations

thank you very much

[ariga]

I use Gunnar's Video Size Calculator (http://www.guthspot.se/video/) to calculate the resizing parameters.

[Delta2]

seems great, but what I want to understand is the calculations it involves

does someone know this calculations ?

[Kika]

640/240=2.666 (strange AR!)
The DAR ist 2.66:1 (really strange)

768/2.66=288.7 (=288)
To get the amount of Scanlines, use a PAR auf 1:1. That's 768x576 in PAL

768/1.094=702.01 (=704)
PAL uses a PAR of 1.094:1

Therefor resize to 704x288, letterbox to 720x576
But i bet, the movie has a bad AR.