1.85:1 aspect ratio

[Thomas-MacFreak]

Why is it that when you choose the width 640, you should have the height set to 352? I thought you were supposed to calculate the aspect ratio like this:

640 / 1.85 = 346 (why use 352 and not 346?)

This seems to be the right way of calculating the height when the aspect ratio is 2.35:1:

640 / 2.35 = 272 (which is right)

Please help me understand

[thoughton]

Chooose what where? You havent said what app you're talking about :P

It kinda sounds like you're referring to ffmpegx, in which case you're in the wrong forum

[Thomas-MacFreak]

No I am not especially talking about ffmpegX. If you do a simple search for aspect ratio 1.85:1 640x352 you will some pages that recommend that you use the height 352 if your width of your 1.85:1 video is 640.

http://divxstation.com/comm/thread.asp?i=14&t=5821&r=0

MacMPEG2Decoder also chooses 640x352 when you use the transform wizard on a 1.85:1 aspect ratio movie.

Why 352?

[Thomas-MacFreak]

I also see when I do a google search that many divx movies has the width x height: 640x352

I have read through the aspect ratio guide here at dvdrhelp, but I have not yet found an answer to my question.

[thoughton]

It is because mpeg video is encoded in 16x16 macroblocks, so your resolutions should be some multiple of 16.

[gonzalimator]

I'm not sure if you are talking about mpg resolution or not, but mpgs need to have a resolution that is a multiple of 16. So in this case, 346/16=21.625. Round that up to an even 22 and you get 22*16=352!

[Thomas-MacFreak]

Thank you very much for your help. Now I understand