[mythtv-users] a little OT: deinterlacing question

jason maxwell decepticon at gmail.com
Thu Feb 15 16:08:08 UTC 2007

If one single frame (30 FPS) is interlaced into 2 separate fields for
broadcast at 60 FPS, then each pair of fields would be from the same
point in time, and therefore should be able to be reconstructed w/o

However, If I understand Stephen's post correctly, the real issue is
that interlaced material is not always generated in such a simple
manner, and that many times each field does represent a new moment in
time. This is sometimes further complicated by the need for pulldown
methods to compensate for different framerate standards. Correct? This
is stupid. Oh well, what am I gonna do about it?

Thanks for the info.

On 2/14/07, Mark Kendall <mark.kendall at gmail.com> wrote:
> On 2/14/07, jason maxwell <decepticon at gmail.com> wrote:
> > I am just curious. Why is deinterlacing so difficult? From what I've
> > read on the topic, an interlaced image is created by breaking a single
> > frame into 2 fields of alternating lines. It seems to me that
> > reassembling the full frames should be as simple as combining the odd
> > and even fields back together. Yet, from what I have read, this will
> > always result in some artifacts, most commonly, tearing (mouse teeth).
> > Why is this?
> You're forgetting that each interlaced field is from a different point
> in time - in PAL terms 1/50th of a second apart (1/60th NTSC). Hence
> you can't just put the two fields back together to make the original
> frame - you no longer have half the original frame.
> The reason it's so difficult is because you have to come up with a
> best guess for that missing half - easy in a static scene, almost
> impossible in a fast moving one.
> Regards
> Mark
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