[MPlayer-users] Re: inverse telecine... not

[D Richard Felker III]

On Thu, Feb 20, 2003 at 03:27:01AM +0100, gabor wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> On Wed, Feb 19, 2003 at 05:37:53PM -0500, D Richard Felker III wrote:
> > [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> > On Wed, Feb 19, 2003 at 05:16:58PM +0000, Jason Lunz wrote:
> > > [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> > > bcboy at thecraftstudio.com said:
> > > > Is there more to the "inverse telecine" noted in the Changelog than the fps fix in 
> > > > libmpdemux/video.c? Because that doesn't actually do inverse telecine at all.
> > > > 
> > > > It looks like mplayer only correctly plays NTSC film dvds that are not
> > > > telecined, and the "telecine" detection in video.c is actually a "not telecine"
> > > > detection -- it detects when a NTSC dvd has NOT been telecined, and thus the
> > > > fps must be adjusted to 24.
> > > > 
> > > > Telecined dvds remain interlaced in mplayer, AFAIK.
> > > > 
> > > > I'm currently checking out the transcode telecine support, which appears to
> > > > do the right thing, reconstructing the film frames from the telecine fields.
> > > 
> > > You're right. Rich Felker is currently working on a _true_ inverse
> > > telecine filter; see his recent posts on -devel. I imagine he could use
> > > your help with testing.
> > 
> > I think I'll go ahead and commit it to CVS soon, but with the
> > understanding that it might change a good bit over the next few weeks,
> > including in ways that make it incompatible with old options syntax,
> > etc. That way users can actually test it and see if it works.
> 
> :)
> 
> 
> btw. (maybe stupid) .. how can i know if my dvd was telecined?

Watch it with -fps 1 and look at the individual frames. If you see 3
good frames followed by 2 horrible ugly interlaced frames, it's
telecined. In fact, it looks a lot worse than normal interlacing. Why?
Well normally if you have interlaced NTSC content, it's 29.97 fps, or
rather 59.94 fields per second, so the two fields shown together are
only about 1/60 of a second apart, which means they look very similar
unless there's REALLY fast motion. But with telecine, 4 frames are
made into 5 by combining fields as follows:

1/1 2/2 3/3 3/4 4/5 | 5/5 6/6 7/7 7/8 8/9 9/9 | ...

where a/b means frame a is shown in the top field and frame b is shown
in the bottom field. The original content is only 24 fps, so that
means when frames 3/4 and 4/5 are put together, you're seeing pictures
that are a whole 1/24 second apart!! So even if there's only minor
motion, the interlaced look is super ugly!

Fortunately, most NTSC movie DVDs use fake telecine, where the actual
stream is 23.976 fps progressive, and the DVD player is responsible
for telecining it as it plays. This means you don't have to do
anything special when watching it with mplayer, and with mencoder, all
you need is -ofps 23.976 to tell mencoder to override the fake 29.97
framerate in the mpeg headers.

But some stuff, especially animation that's originally drawn at 24 fps
but then made for airing on television in the US or Japan, is actually
'hard telecined' before encoding the DVD. :((


Rich