[Open-graphics] Interlaced vs. progressive scan HDTV

[Timothy Miller]

On 7/3/06, James Richard Tyrer <tyrerj at acm.org> wrote:

> The question that I have is how an LCD is updated.  Does it update with
> a (progressive) scan like a CRT or is it double buffered and updates the
> whole screen at the vertical sync pulse?  This is going to make some
> difference in how a movie looks but there isn't anything that the
> graphics board can do about it.

The LCD display is like an array of memory cells, but they can only be
updated one at a time, so they're updated in a raster-scan pattern.

> LCD computer monitors would present different frame rate issues.  Many
> of them are only 60 fps and would be treated just like TV, but there are
> some that support higher vertical refresh rates.

They usually support higher rates, to very little useful effect.  That
is one way to reduce the smear.

> I would suggest that
> we support 72 fps since this is 3 times the movie frame rate which would
> display movies a little better than 60 fps since there would be no
> stutter (each progressive frame shown 3 times).

With the sample-and-hold, I don't think this would help.  When the
pixels do change, you're still going to see both the hold values and
the new at the same time.