[MPlayer-users] Converting 512:272 to 480:480 with aspect=4/3?

[romildo at uber.com.br]

On Sat, Jan 17, 2004 at 02:39:29PM -0500, D Richard Felker III wrote:
> On Sat, Jan 17, 2004 at 02:37:06PM -0200, romildo at uber.com.br wrote:
> > On Thu, Jan 15, 2004 at 07:07:11PM -0500, D Richard Felker III wrote:
> > > 
> > > On Thu, Jan 15, 2004 at 11:54:32PM +0100, Svante Signell wrote:
> > > 
> > > > Need advise hoe to expand/scale/crop an avi clip of size 512x272 to an
> > > > mpeg2(SVCD) clip of size 480:480 expanded to 640:480 when displayed.
> > > 
> > > You have to do the math to work out the right sizes,
> > 
> > Is the math the following?
> > 
> > 	width ------------------ height
> > 	640   ------------------ y
> > 
> > 	width * y = 640 * height
> > 
> > 	y = (640 * height)/width
> > 
> > In the example above of a frame size 512x272 we have y = 340.
> 
> Yes.
> 
> > > or else get
> > > mencoder to do it for you with fancy use of the automatic options for
> > > scale.
> > 
> > How would that be achieved?
> 
> You'd have to think about it some. See the man page for the various
> ways to automate the sizes expand and scale select (using negative
> w/h). You'd probably also need to use the dsize filter to set the
> desired aspect. It's complicated and I don't feel like working out
> exactly how it should be done, especially since I think it's better to
> do things manually to be sure you stay on multiple-of-16 boundaries to
> maximize quality.

I have tried but was not able to figure out how to use the automatic
options for the scale filter in this example. Can anybody enlighten
here, at least with a command line?

Regards,

Romildo