[mythtv-users] Frame by frame playback - 3 good, 2 "ghosty"

Michael Heironimus mkh01 at earthlink.net
Thu Jan 3 01:41:51 UTC 2008

On Wed, Jan 02, 2008 at 03:31:45PM -0500, Jay R. Ashworth wrote:
> On Wed, Jan 02, 2008 at 12:23:06PM -0800, Dale Quigg wrote:
> > I thought I saw my question in the forum archives, but I couldn't find
> > it again.  I've noticed that when going "frame by frame" in a show,
> > that there seems to be a repeated pattern of 3 "good" frames" and 2
> > "ghosty" frames (especially if there is horizontal movement).   This
> > happens whether I use "Default" or "Highest" recording quality.  I've
> > also tried various settings for deinterlacing, but I've not seen any
> > change in the output.
> Yup, it's interlace you're seeing.  3:2 pulldown from 24fps source
> interlace, to be specific.  For comparison, record a local news
> broadcast (preferably one that has *not* gone hi-def yet), and frame
> through that.
> Deinterlacing *can* help, though I don't know precisely which mode will
> work best for you...

The 3:2 pulldown is also commonly called "telecine", which might help if
you searching the web for information. Deinterlacing is unlikely to help
because the process creates one extra frame per each four in the
original source, though it may help with other playback problems.

The real question is this: do you notice it when you play it at normal
speed? If not, the answer is "play it at normal speed". If you're
watching ordinary NTSC TV the majority of the content you see has
probably gone through this process. For that matter, DVD players do it
on the fly most of the time.

If you're looking to archive the material you can often (mostly) undo
the process with an inverse telecine ("IVTC") or pullup filter.

Michael Heironimus

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