[rec.video] Image Format Sizes

crowl@cs.rochester.edu (Lawrence Crowl) (03/17/90)

In article <132563@sun.Eng.Sun.COM>
poynton@vector.Sun.COM (Charles A. Poynton) writes:
>... the case for 1920x1080 as leading to economical framebuffer
>implementations (due to its total of two megapixels) and offering an
>excellent compromise among the choices proposed for picture line count
>(966, 1035, 1080 and 1152).

Why not 2048x1024?  This is easy to address, easy to store, exactly and two
mega-pixels.  Why is it that the proposed standards have picked such bizzare
numbers?  If people are serious about making images easy to manipulate on
computers (and only the terminally unimaginative would not be), then we should
choose a frame size that is very easy to manipulate on computers.

>Experts agree that a single international standard [for frame rate] cannot be
>achieved at any one of 25, 29.97 or 30 Hz.  A very large fraction of
>broadcast programming is currently originated at 24 Hz so that rate is
>amenable to broadcast.  If a frame rate other than 24 Hz is adopted for HDTV,
>then movies will continue to be produced on film to assure continued access
>to the international markets that 24 Hz film currently enjoys in cinema,
>television, videotape and videodisc distribution.

I have two concerns.  First, the frame rate should be high enough so that
there is no observable flicker.  Second, the frame rate should not be close
enough to existing power line frequences to cause the screen to beat with
flourescent lighting.  Which rates have which problems?

-- 
  Lawrence Crowl		716-275-9499	University of Rochester
		      crowl@cs.rochester.edu	Computer Science Department
	  ...!{ames,rutgers}!rochester!crowl	Rochester, New York,  14627

sehat@iit (Sehat Sutardja) (03/20/90)

In article <1990Mar16.205807.5971@cs.rochester.edu>, crowl@cs.rochester.edu (Lawrence Crowl) writes:
> Why not 2048x1024?  This is easy to address, easy to store, exactly and two
> mega-pixels.  Why is it that the proposed standards have picked such bizzare
> numbers?  If people are serious about making images easy to manipulate on
> computers (and only the terminally unimaginative would not be), then we should
> choose a frame size that is very easy to manipulate on computers.
> 

The main reason to this is because in many digital motion video compression
algorithm such as the motion compensated DCT, some extra video memory area
may be needed to store some temporary image data. If you use all of the 
frame buffer, then you need additional storage chips to do this function.

Since the reduction in resolution is insignificant compared to the reduction
in cost, the trade off is justifiable.

-- 
Sehat Sutarja,

{decwrl!sun}!imagen!iit!sehat	| Integrated Information Tech.
sutarja@janus.Berkeley.EDU	| Santa Clara, CA. (408)-727-1885