interlaced encoding and field order

[bREAkDoWN]

I'm doing some experiments with interlaced encoding with xvid, but i can't find a way to set the top-field-first attribute in the encoded stream. Divx has an option in the encoder to select top field-first but i haven't been able to find such an option in the xvid interface. Is there a way to set that attribute? I would need it because i'm trying to play these interlaced videos on a standalone player where the difference between a wrong setting of the top-field-first attribute is very very evident.
And if i send to xvid the fields swapped spatially (for example with avisynth swapfields()) i'm able to fix the temporal aspect of the problem, but doing so i introduce a spatial problem (or at least that's what i think it's happening ;))

[scharfis_brain]

instead of swapping the fields use:

doubleweave.selectodd

[sysKin]

XviD's internal API has a flag for top-field-first but VfW's gui doesn't. I'm not really sure what you can do, other than compile XviD yourself with the flag set...

Radek

[bREAkDoWN]

First of all thanks and happy new year to both of you! :)
Then i must say that doubleweave.selectodd is an optimal workaround for the problem. Encoding with fields merged betwen adjacent frames has the same effect as changing the field display order during playback. And that's exactly what i needed to do.
Anyway, since Xvid handles the top field first attribute, but, as sysKin says, it's hardcoded in the source, i hope that future versions will include an option in the gui to set this flag.
Any developer out there? ;)