[MPlayer-users] Reverse PAL telecine

[Rich Felker]

On Thu, Mar 06, 2008 at 10:04:36PM -0700, Bryan Stillwell wrote:
> A couple years ago I bought a PAL DVD while on a trip to England.  Then
> earlier this week I decided I would make a high quality backup copy of
> the disc to my computer.  The problem is that I haven't been able to
> figure out what the right options would be to undo the telecine on it.
> 
> To troubleshoot it I dumped 150 frames (6 seconds @ 25fps) to disk to
> figure out what was going on:
> 
>     http://www.bokeoa.com/pal_telecine/
> 
> You'll notice that frames in multiples of 25 starting with frame 9 are
> the cleanest (9, 34, 59, 84, 109, 134), but between those frames it goes
> from slight interlacing to full interlacing and back.  I also noticed
> that the interlacing seems to take 4 lines instead of the normal 2
> (even/odd).  To make sure mplayer wasn't doing any scaling during the
> dump that might have caused this, I used the '-aspect 720:576' option:
> 
>     VO: [png] 720x576 => 720x576 BGR 24-bit

This IS doing scaling, from 4:2:0 sampled YUV to 4:4:4 sampled RGB.
That's the cause of the 4-line oddness. You need to make sure
interlaced scaling is being performed by explicitly loading the scale
filter with the right options rather than letting MPlayer do it for
you.

> I found that some of the deinterlacing filters seem to clear up the comb
> effect some, but as I understand it, that cuts the quality in half
> (which isn't what I want).  Ideally I would like to convert from the
> 25fps output back to the original 24fps in the cleanest and best quality
> way possible...
> 
> Has anyone run into this form of telecine before and have any hints on
> what I should do to reverse it completely?

Seriously, you should find a good bittorrent site and download a
proper rip from the NTSC disc. From what you've said, I'm 99% sure
this video was first telecined (lossless operation) then framerate
converted from NTSC to PAL with temporal interpolation (highly lossy
operation even without telecine, and even worse when applied on top of
telecine). Basically what you bought isn't worth the media it's stored
on, but since you already paid for it you shouldn't feel bad about
helping yourself to a proper copy.. :)

Rich