[MPlayer-users] probably my usual stupid question of the week

[D Richard Felker III]

On Fri, Apr 16, 2004 at 11:03:12AM -0400, Aaron Peterson wrote:
> > Crop should probably go first. No need to use -xy and -zoom. They're
> > rather strange. Just use -vf crop=...,scale=w:h and fill in the width
> > and height to use. There are tricks to get mencoder to compute them
> > for you, but it won't align them at multiple-of-16 boundaries so
> > you're best to just figure out the right size yourself. Normally it's
> > 640x272 (2.35:1), 640x288, 640x352 / 640x368 (16:9), or 640x480 (4:3).
> 
> Okay, so the original video is 720x480, aspect 1.78:1.  So I ran
> cropdetect, and it tells me it wants to crop a picture 720 x 366.  So I
> calculate the equivalent 640 x N ratio, and N=325 (almost). Anyway, this
> is not a multiple of 16, so I divide by 16 which is 20 something, then
> multiply 16 by 20 to get 320.  So I just want to confirm that this is the
> correct method to go about all this, I would want to scale to 640x320?  Or
> should I use one of the measurements you gave above instead?  If I should
> use one of the above, how would I have figured out which one?

Yeah, just round to the closest multiple of 16. So in your case, 320.

> If I didn't want to scale down the video, but did want to preserve the
> aspect in a way that most players understand, do i need to use
> scale=720xXXX ?

Rescaling is the only way that most players understand... If you want
to keep the original size you'll have to use insanely high bitrate
anyway.

Rich