Video Magically Resizing - Driving me crazy

[Komencanto]

I am encoding an MPEG1 to divx. Look below for the resolution. Notice anything interesting. It claims the video resolution is 352*240 (4:3) . Say what? 352x240 does not equal 4.3 it equals 1.444x1 . But thats just the beginning. When I encode this mpg to avi, magically, depite me having all of the resizing/cropping/whatever options disabled completely, the other movie opens in both BSPlayer and WMP differently, the avi 32 pixels shorter than the other. This makes the people look sizably fatter than before.
I have done the transfer also with Xvid, and in Divx doctor, and used 3 varieties of VirtualDub, all to no avail, it always turns out the same.

But thats not all, when I analyse the original mpg and the avi in avicodec they both claim the same (incorrect) resolution!

Please help if you know how, or I don´t think I´ll be able to sleep tonight =/

[willy_annand]

Welcome to the wild world of DivX.

The DivX format has to be the worst video format developed to date.
No wait, I forgot about Microsft Media Format.
Or the "Real" format.

OK, it is in the top 3...

With the prices of Writers and Media coming down, do yourself a favour and buy a DVD Writer and encode to MPEG2 format. Much better quality.

[Komencanto]

Hold on a moment, that seems a bit harsh. MPEG2 is a very high bitrate codec, not exactly appropriate for sending files over the internet. I would like to use it, but I want high compression, and for that divx and xvid are better.

[bugster]

Mpeg was developed for TV display, where pixels are not square. The display apsect ratio (DAR) of an mpeg is stored in the data stream and the decoder/player resizes as required. For example, full D1 resolution for DVD is 720*480/576 (NTSC/PAL). This can be displayed in 4:3 or 16:9 aspect ratios, both encoded with exactly the same number of pixels in both dimensions. When played on a PC, proper SW DVD players like PowerDVD and WinDVD will play them with the correct aspect ratios. Some others like WMP will not.

FYI, 352*240 is the standard res for VCD (NTSC), which only supports 4:3 DAR. Again, the pixels are not square so there is no direct relationship between DAR and res.

So, when encoding an mpeg to Divx you have to take all this into account. That is the source res, the source DAR and the required results.

[Komencanto]

Ok, I think I understood that. So if I want to DivX copy to open in the same aspect ratio as the original, what should I do?

Hey, anyone ever noticed that this video stuff is a complete mess? You´ve got NTSC and Pal, MPEG124, heaps of codecs with lots of options to figure out, aspect ratios, bitrates, frame rates etc etc. And none of them works like you expect them to.

Every time I try to do a simple conversion of files I download I have to learn new things.

[bugster]

I am not an expert at encoding divx (by a long shot) but you have to select a resolution for the divx that matches the DAR of the mpeg. So for 4:3 DAR, the divx could be 640*480 or 320*240 etc.