[Tig] 24p frame rate

Bob Friesenhahn bfriesen at simple.dallas.tx.us
Mon Aug 4 23:47:49 BST 2008

On Mon, 4 Aug 2008, beau tardy wrote:
> I would argue that the reason it looks ok in film is that we watch 
> films projected on a large screen.  Film is a mechanical medium with 
> light projected thru it, whereas TV and computer monitors are 
> electronic media and have light beaming at us.  This fundamental

There is something else about film.  Each film frame is flashed 
several times.  Before this trick was figured out, 24 frames per 
second looked really bad.

LCD and Plasma displays are becoming quite popular.  These 
technologies are not capable flashing the frame several times like 
film.  Recent LCDs are increasing their internal update rate (e.g. 
120hz) so that they can interpose frames and play other tricks to try 
to make the video updates more acceptable.

It makes sense for a true digital display to be a frame store (memory) 
like in a computer display card.  If the content does not change, then 
the memory does not need to be updated.  Only parts which change need 
to be updated.  The whole notion of "refresh" is quite dated because 
it assumes that the display medium is semi-persistent.  This is true 
for CRTs and DLP with a color wheel or wobbulation.  Refresh should be 
a function of display implementation and not part of the video stream. 
The only reason why whole frames need to be sent at all is to handle 
channel changes, temporary loss of signal, or when the set is first 
turned on.

Regardless, except for the ease of transfer to film, there is nothing 
magical about a particular update rate.  The most magical thing about 
24P is what the 'P' signifies.

Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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