[MPlayer-users] Changing aspect ratio within DVD title

Adam Nielsen a.nielsen at optushome.com.au
Tue Aug 12 05:33:35 CEST 2003

> > Have you instead tried finding the exact locations of the aspect ratio
> > switch?
> That would require a lot of trial-and-error, because mplayer doesn't have a
> function to step forward frame-by-frame (that would be _extremely_ useful!).

That's true - perhaps you could try to find another video editing program that 
will let you do this, then take the frame numbers and copy them across into 

> That's why my idea was to convert the title to a series of JPEG images

The two ideas are basically the same, except with JPEGs you're converting them 
into sections of one frame each, whereas the other way you'll be converting 
them into sections of many frames each - plus you'll be avoiding 
recompression to and from JPEG format.

Mind you, once you've extracted the jpegs you'll still have to look through 
them for aspect ratio changes, and once you find them you'll be able to see 
the frame number anyway from the filename.

> Uhm ...  I've never tried to join AVI files.  The "transcode" package
> contains a tool called avimerge, but I'm not sure how well that would work.

As long as all the video files have the same resolution, framerate, codec, 
etc. it works flawlessly.  Audio could be a problem if it's compressed (e.g. 
MP3), but you can do the whole operation without audio and then just add the 
full audio track at the end to get around this.

> so I would have to scale the 16:9 parts and add black bands appropriately.

Definately!  ...or you could add black vertical bands to the 4:3 part, if you 
want the final file to be in widescreen.

> Has anybody tried that before?  Any caveats?  Would it be indeed easier than
> the JPEG images approach above?

Apart from possible problems I mentioned with the audio tracks, there's no 
other difficulties I'm aware of.  And as long as you're able to get the exact 
points to split the movie then yes, it is a lot easier than using JPEGs (and 
a lot better quality too!)

> I would just prefer to avoid re-inventing the wheel, or spend an afternoon
> finding out that it doesn't work.  But I'll try if nobody else has any
> experience on this.

If you're worried, just extract a few seconds in the 4:3 part, and a few 
seconds in the 16:9 part and try joining those together, just to get the hang 
of it.  Then if you're happy with the results, you can spend the extra time 
doing it with the whole movie.


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