[MPlayer-users] Re: Ripped DVD got wrong aspect ratio?

[Daniel Pittman]

On Fri, 08 Nov 2002, Diego Zuccato wrote:
> I'm just startingmy DVD-ripping experience. I bought "Saving private
> Ryan" and ripped it (w/ vobcopy).
> If I play the vob in mplayer it's all OK. So I did a 3 pass encoding:

[...]

> It all goes well (well... except it takes about 5h20', but I think
> that's quite normal, even on an AthlonXP 1900+) and the file is 2037M
> (so not more than the 2GB limit), BUT when I play Ryan.avi it's 4:3
> instead of 16:9 ! :-(
> 
> Do I have to use -vop scale as TFM says in 2.4.2.2 (isn't it for VCD
> only?) ?

No, that's not the only solution with MPEG4 output. One is to rescale
the movie to correct for aspect ratio before encoding.

The second, and the one that I use, is to embed the aspect ratio
information in the MPEG4 stream and have the scaling applied by the
final player.

This works well; all you need to do is add the right value to the
lavcopts.

Basically, give the argument 'aspect=...' where ... is the right
floating point number for the aspect ratio. This is a floating point
number somewhere between 0.3 and 3.0.

The only pain with it is that an exact floating point compare is done in
the code, not an inexact one, so that '1.33' is rejected as an aspect
ratio, but '1.333333333333333' is fine...

The following aspect ratios are accepted:

        1.333333333333333 (4:3)
        1.777777777777778 (16:9)
        2.21              (2.11:1, presumably)

Anything else is rejected as an invalid aspect ratio. If you don't
specify the option, the mpeg4 stream is marked as having a square aspect
ratio (1:1) and you need to specify aspect in the player later.


I use embedded aspect ratio information all the time myself and have not
yet seen any ill effects from it.

         Daniel

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