question about a Vdub performance option something, question, default, because

andy

So far I'm using this option as default:
Options/Preference/AVI - Directly decode YCbCr(YUV) sources
and
Video/colorDepth: a) Decompression format (Autoselect), b) Output format to compressor (same as decompr. format).
and
XviD decorder's output format - No Force

My question is _ Would it be better if I disable this option in Vdub and enable the colourspace YV12 on XviD decorder, so the Xvid will handle it and output in YV12 format ?
and something else...-what is the YUV420 format? because this is what I get when I recompress  with quot;normalquot; or quot;full proce. modequot;.
Is quot;Fast recompressquot; in Vdub the only way to output YV12?

Thanx 4 ur time

...well can anyone at least tell me if quot;YUV420quot; is the quot;I420quot;?
because if it is then:
YV12_is_ 8 bit Y plane followed by 8 bit 2x2 subsampled V and U planes.
I420_is_8 bit Y plane followed by 8 bit 2x2 subsampled U and V planes.
~These formats are very similar if I can't say identical, the only difference is the U and V plane order which is reversed.

Thanx anyway.