[MPlayer-users] Scaling and Cropping

[Graham Lawrence]

> Date: Sun, 19 Aug 2012 21:42:52 +0200
> From: Reimar D?ffinger <Reimar.Doeffinger at gmx.de>
> To: "MPlayer usage questions, feature requests, bug reports"
>         <mplayer-users at mplayerhq.hu>
> Subject: Re: [MPlayer-users] Scaling and Cropping
> Message-ID: <20120819194252.GA27141 at 1und1.de>
> Content-Type: text/plain; charset=iso-8859-1

>
> I think that means you are encoding incorrectly.
> Either you need to add a scale filter to do the aspect scaling (not
> such a good solution since it costs quality) or you must make sure
> the proper aspect is encoded in the file, e.g. via -lavcopts autoaspect.
>
I've been using "aspect=16/9".  When I first considered encoding my
own dvds it became quickly apparent that this is a formidably complex
subject.  But as someone kindly wrote model mencoder command lines for
PAL and NTSC in 7.8.5.1 and 7.8.5.2 of Mplayer's online documentation,
I figured I could incorporate these in a script and possibly avoid the
need for perhaps 2 years intensive study of the subject.  These are
the source of my use of "aspect=16/9".  I've had to modify the script,
largely according to the information provided in 7.2 of Mplayer's
online documentation, but the end result is extremely satisfactory.

Of more than 400 encodes I have a residue of about 25 problem encodes,
the largest group of which involve failure of the presented image to
fill the screen in at least one direction.  In all but one of this
last group the image remains as a small rectangle in center screen,
whether I show the dvd, the uncropped encode movie.2, or the cropped
encode movie.avi.  The one exception is the one that prompted this
enquiry.  It is unique in that it will scale in the horizontal plane,
but not in the vertical, and it is this fact that makes me think this
is entirely a problem with scaling.

I do nothing about scaling in my encodes, relying on Mplayer's
automatic scaling at playback time.  As this never happens with this
group, I think that the source of the problem must lie in the
structure of the original dvd.  Mplayer has the monitor size,
1920x1080, and it has the video image size, say 720x480, so scaling
should be simply the application of whatever numerical algorithm is
appropriate in each direction.  That this process is automatic with
Mplayer playback, but does not occur with this group, must mean that
they include some indicator that disables Mplayer's automatic scale
process.  Or do I have something amiss in my understanding here?

-- 
Graham Lawrence