Re: [MPlayer-users] copy protection

[Corey Hickey <bugfood-ml@xxxxxxxxxx>]

[Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
Damion de Soto wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
>
>
> D Richard Felker III wrote:
>
> > Actually, there is a rather nasty copy protection scheme used in many
> > DVDs... I'm halfway being sarcastic about this, but somewhat serious:
> > Nasty broken telecine. Discs which mix hard and soft telecine at
> > random, or use very weird telecine patterns which are difficult to
> > detect. 
>
>
> I see heaps of problems relating to telecine, and see various warnings 
> etc on some of my DVDs that use it.
> Can someone explain exactly what hard/soft telecine is and why mplayer 
> plays it fine, but you can't rip/encode it. (or have i got that wrong too?)
> Or point me to a website, i've googled a bit, but the most detailed 
> description I found was 'telecine - converting film to video'
>
> thanks


The best decription I've found of telecine and all the associated
framerates is here:
http://www.divx.com/support/guides/guide.php?gid=15

When we say hard or soft telecine we refer to the stage at which the
telecining occurs. Soft telecine video is 23.976 fps, and it is intended
that hardware video players telecine this before sending the signal to a
television. Mplayer says "telecine detected", but doesn't actually do
any telecining because there's no need to do so for a computer monitor;
mplayer just displays the video as-is, at 23.976 fps.

Hard telecined video has been telecined in advance before being stored
on the disc. Mplayer says this is progressive video, because the data
doesn't say "telecine me". :) Since the telecining has been done
already, the video is at 29.97 fps, and mplayer switches to that rate.
Though not all 29.97 fps video is hard telecined, it seems that with
regard to DVDs that is usually the case.

Encoding soft-telecined video is not a problem. You just have to specify
-ofps 23.976 so mencoder doesn't try to make 29.97 fps video.
Hard-telecine isn't a problem either now, because Richard's detc filter
can selectively drop the extra fields and leave us with nice, clean
23.976 fps.

The problem is that some DVDs start out soft-telecine, then switch to
hard-telecine, then back to soft, etc. The interval between switching
back and forth can be variable and completely random - I've even seen
DVDs where that switch after less than a second. At the moment, the detc
filter can't properly handle this situation:
http://www.mplayerhq.hu/pipermail/mplayer-users/2003-July/035262.html

The other problem Richard refers to, if I understand him correctly, is
when the hard-telecine doesn't follow the usual 3:2 pulldown pattern,
but some other weird method of converting 23.97 fps to 29.97 fps.

-Corey

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