Aspect ratio issue when converting to DivX

[a.wright]

Hi,

I am having some problems with aspect ratios when converting MPEG2, vob and avi files to DivX. Basically DivX appears to be fixing the aspect ratio regardless of what it should actually be.

I have included a link to the detail of the problem to save writing it all out again that I posted over on the DivX forums. It is one of those problems which is really bugging me because I obviously don't understand.. and I really want to understand!

http://forums.divx.com/groupee/forums/a/tpc/f/401101651/m/711107662

Any help/comments would be most welcome!

Andrew

[Delta2]

Here is some AVI images converted from a DVD PAL 16:9 source

full 640x272





I used DGIndex + AVISynth + AutoCrop to get rid of letterboxes and better use of space

[a.wright]

The problem is I want (and have been) keeping the full PAL 720x576 resolution so that I can still get a decent image on my TV. Thus if I have a 16:9 source I want it to view exactly the same once converted to DivX but for some reason, by keeping the 720x576 frame size, it won't display properly.

I also have an Archos AV700 PMP which is 16:9 so a 16:9 source converted to DivX should also fill this perfectly.... I am thinking something has changed in the latest version of the DivX codec.

[mats.hogberg]

I'm thinking: Many AVI players treat all AVI to have a 1:1 PAR. I suggest you abandon your idea of keeping the frame size when going mpg -> AVI.

/Mats

[Delta2]

I'm thinking: Many AVI players treat all AVI to have a 1:1 PAR. I suggest you abandon your idea of keeping the frame size when going mpg -> AVI.

/Mats

yes, keep de frame size and don't crop the image

[nattawat]

4:3 ratio works for me perfectly when converting from DVD to AVI.

This include the black border though, not-cropped.

[a.wright]

Still confused!

Example:

I recorded, edited and output a 16:9 DV-AVI at full PAL resolution of 720x576. I converted to MPEG2 and authored a DVD which displayed perfectly on a widescreen (16:9) TV. I then converted to DivX (tested with both the original avi & vob files) which also played perfectly on my widescreen (16:9) Archos PMP.

So in this case the original 16:9 video was converted to DivX and resulted in a .divx file that displayed as a 16:9 image, with the correct aspect ratio on my PMP. It also meant that if I connected the PMP to the TV, I still retained the full PAL frame size.

Since the latest Divx update, if I repeat the above exercise, the converted file now displays as a 4:3 image in the middle of my PMP widescreen display and everything in that image looks squashed and thin.

Does that make what I am trying to explain a little clearer?

Andrew

[jagabo]

Did you set the aspect ratio in Divx's config dialogs?

[celtic_druid]

You can check/change the PAR with MPEG4Modifier.

[a.wright]

I have set the aspect ratio yes but the output seems to be the same regardless, which is what is confusing me. What is the difference between pixel ratio & display ratio then? I thought that the only difference between 16:9 & 4:3 PAL was the shape of the pixel as the resolution remains the same regardless.

It looks like MPEG4Modifier may do the trick but it seems a bit of a hassle when there was no need for the DivX codec to change anything. And like I said, it was working perfectly before the latest update.

[jagabo]

What is the difference between pixel ratio & display ratio then?

It's basically just two ways of specifying the same thing.

I thought that the only difference between 16:9 & 4:3 PAL was the shape of the pixel as the resolution remains the same regardless.

That is correct for DV and DVD. An arbitrary digital video can have any combination of frame size and aspect ratio though.

Microsoft never defined a standard for specifying aspect ratios in AVI files. So aspect ratios are defined by some private data within the codec or by a program adding extra hunks to the AVI (the RIFF format on which AVI is based is flexible enough to support this). So not all applications respect any particular codec's or other programs' aspect ratio setting.

[a.wright]

So not all applications respect any particular codec's or other programs' aspect ratio setting.

So I guess then that something has changed in the DivX codec and/or Converter application in the latest update that is causing this. I would be interested to know if anyone else can actually maintain full PAL resolution after conversion and keep the same aspect ratio.

Andrew