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List:       xine-devel
Subject:    Re: [xine-devel] Detecting tvtime filmmode toggle
From:       Billy Biggs <vektor () dumbterm ! net>
Date:       2005-12-03 16:32:36
Message-ID: 20051203163236.GH3299 () dumbterm ! net
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Jason Tackaberry (tack@sault.org):

> A fair amount of my captured television (and even quite a few of my
> DVDs) causes the tvtime plugin to regularly toggle back and forth
> between film mode.  Presumably this is caused by the telecine pattern
> getting reset on a scene change (where here "scene change" can even mean
> simply a cut to a different view during the same scene).  The problem is
> that continually toggling film mode causes judder in the video.

  For a DVD of any film material (movies), it's very unlikely that the
telecine pattern is breaking.  What's much more likely is that the DVD
is switching between telecine-as-flags mode and expanded-telecine mode.
DVDs let you optionally encode the video  at 24fps but with flags
(top-field-first and repeat-first-field) indicating how to convert it up
to 59.94 fields per second.

  The fix is to "seed" tvtime's algorithm whenever you switch between
these modes.  Detecting this is not too bad.  See the "movietime"
sources (my crappy old DVD player) for how to do this.

  For television content, I have seen examples where the show was shot
at video speed (24fps), then clearly they edited it using video editing
equipment at 59.94 fields per second.  A good example was the show
"Power Rangers" which flipped between lots of differently recorded
medias, and seemed to have everything edited at video speed.  For this
content, I have a two-pass off-line algorithm in the "reetpvr" sources
that was working pretty well, but really I don't know if this problem is
worth solving.  Your idea of shutting it off if the switch rate is too
"noisy" seems like a good idea.

  I'm curious to hear of any results or conclusions you make,
  -Billy



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