[theora] YUV4MPEG RGB<->YUV subsampling

[dos386]

Hi

anyone has good informations on YUV4MPEG file format, including
subsampling and the colorspace conversions ? There are various
informations around (including Theora spec, png2theora.c) , the
problem is that they are incomplete, messy and contradicting.

My great YUV player plays now somewhat (even one file from MPLAYER
that MPLAYER itself (!!!) can't play correctly), but it's based more
on try-and-fail guesses than facts ...

What is the __CORRECT__ bunch of formulas for YUV<->RGB conversion,
preferably in one step without unuseful constant calculations ? Does
the same colorspace cover Theora, MPLAYER output (decoding proprietary
movies), and JPG, or are there multiple ?

Can a YUV4MPEG file have an odd height or even width ? It breaks the
subsampling of course, and playing it in MPLAYER ...

Are there other subsamplings than 1/2 horizontally and 1/2 vertically
? Seem defined, but anyone uses them ? All files I've seen so far had
1/2 horizontally and 1/2 vertically only.