[Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
Green, Shaun writes:

> But it's MUCH less intuitive and harder to setup and get the right aspect
> ratio. By specifying crop, then scale, yes you actually are scaling first,
> which gets the aspect ratio correct, then you crop the black bars away. This
> is intuitive and easy to understand.

You can use something like scale=640:-2,crop=... to automatically get
the correct aspect.  Off course this will not make the height a
multiple of 16.  Maybe there should be some options for scale to get
some modulo values.  This was discussed some times ago but I think no
conclusion was reached.

Just in case you want to know, in scale=W":H",crop=W':H' with a movie
size of WxH (usually 720x576 or 720x480) with an aspect A (usually 4/3
or 16/9), you have the following relation:

 W"        H     W'
--- = A * --- * ---
 H"        W     H'

Mmm, I think I'm gonna write my encoding cookbook...

Kim Minh.

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