[MPlayer-users] RFC: docs update for "how to create a high quality DVD rip"

[Jason Tackaberry]

In the current documentation, section 7.11 explains how to create a high
quality DVD rip.  This section was contributed by Samuli Kärkkäinen
based on an email I'd sent to a friend some time ago.  I've learned a
few things since then, and find this text is badly in need of an update.

Before submitting to the MPlayer docs team, I'd like to hear some
feedback from you guys.  Ping especially Rich, so that he might point
out any technical errors in his usual, ehm, terse but informative
manner.

You can read the new section here:

	http://sault.org/~tack/menc-feat-dvd-mpeg4.html

One point I detail is the fact that image dimensions should be a
multiple of 16.  I've read this in numerous places, and it seems to be
conventional wisdom.  Unfortunately, I'm not entirely clear on why this
is the case.  Some inferences:

     1. If, say, the height offset is a multiple of 16 plus 4 pixels,
        the latest row of macroblocks will need to be padded with 12
        rows of pixels, which wastes bits.
     2. libavcodec sees the padded pixels as black, and so wastes bits
        preserving a sharp edge that is never seen.
     3. Some windows (and possibly linux) players can't deal with
        resolutions not divisible by 16 and crash or show visual errors.

Now, as far as 1 and 2 are concerned, is this any worse than cropping
away perfectly good pixels, or scaling video up to the nearest multiple
of 16?  If so, why?  Or, what's the _real_ reason for the multiple-of-16
rule?

Secondly, the crop y-offset should be a multiple of 4 if the video is
interlaced or telecined, but is this still true if deinterlace or pullup
appears in the filter chain before crop?  It seems to me that after
deinterlace/pullup, any multiple of 2 is fine, but sometimes these
things can be elusive so I don't want to make that claim for sure
without confirmation.
  
Please let me know any problems, changes, or additions I should make to
the text.  I'd like to forward it onto the docs team ASAP.

Thanks,
Jason.