Re: Survivor going HD!

In article <25340-480DE5F0-568@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
doob@xxxxxxxxx wrote:

Guardsman wrote:

If your TV-watching includes many such scripted shows, it wouldn't
be a waste to get a 1080p display that can do 3:2 inverse telecine.
(Or even better, one that can do 5:5 pulldown at 120Hz.)"

I LOVE the 5:5 pulldown. :-)

(not a clue as to what all this stuff means)

- When a show is filmed on film, it's shot at 24 frames per second.
- When a show is recored on video tape it's recored at 30 frames
per second.
- When a show is broadcast on TV it's broadcast at 30 frames per
second (for both film and video tape).

If nothing was done to compensate, shows filmed at 24 frames per second
would run 25 % faster than they should (i.e. everything would be in
"fast-motion"). A 90 minute movie would only take 72 minutes to
broadcast.

For normal TV (i.e. non-HD TV) each frame is divided into two fields,
one field has all the odd lines and the other all the even lines. The
fields are alternately drawn on the screen. 30 frames per second, 2
fields per frame = 60 fields per second displayed thusly:

1e, 1o, 2e, 2o, 3e, 3o, 4e, 4o, 5e, 5o, 6e, 6o... etc.

Which works fine for video tape.

For film, each frame is still split up into two fields but the order the
fields are shown in changes:

1o, 1e, 1o, 2e, 2o, 3e, 3o, 3e, 4o, 4e, 5o, 5e, 5o, 6o, 6e... etc.

This is known as a 3:2 pull-down. Three fields from the first frame are
shown, then two fields from second frame, then three fields from the
third, etc.

If we put these two streams next to each other we can see the advantage:

1e, 1o, 2e, 2o, 3e, 3o, 4e, 4o, 5e, 5o...
1o, 1e, 1o, 2e, 2o, 3e, 3o, 3e, 4o, 4e...

In the time it takes to show 5 frames of a video taped show, you only
get to display 4 frames of a filmed show. Slowing the filmed show down
by 25%.

With HD, we get new display standards, of particular interest to this
discussion are 720p and 1080p. The p stands for "progressive". In both
of these formats the frames are not broken up into fields, each frame is
displayed as a single field, 24 or 30 times per second*, depending on
the source material.

Some higher end sets can do what's called a "3:2 inverse telecine", or
"deinterlacing", or others terms depending on the marketing department
involved. What happens is the electronics in the TV detect that the show
is being displayed using a 3:2 pull down, dissects the stream and throws
away the repeated fields. It then mushing the matching fields together
to recreate the original frames, thus making it progressive.

Some DVD players can do this as well.

How the sets handle displaying a 24 frame per second stream will vary
depending on the make and model. LCD displays can simply slow down their
refresh rate and display the show at 24 frames per second. That's much
too slow for CRT (tube) or plasma displays. One simple solution is to
display the show at 72 frames per second and displaying each frame 3
times in a row.

I have no idea what a 5:5 pulldown is, but I suspect it means each frame
is displayed 5 times in a row at 120 frames per second. This may be
useful for some people who are extremely sensitive to screen flicker,
but it's not going to be noticeable for most people**. It's a complete
waste of time for LCD based TVs as they have no phosphor decay.


* Depending on the technology each frame may be shown twice to maintain
60 frames per second.

** There may be TVs that are manufactured in such a way that the effect
would be noticeable. But since the amount of information (24 or 30
frames per second) doesn't change, it's overkill. This doesn't apply to
computer or video games which would be capable of spitting out 120
separate frames per second.
.

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