[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: "True", "True" (H)DTV....and the relation to 720/60P Display Syst ems



In a message dated 97-10-09 03:38:59 EDT, Tim wrote:

<< Back to simple math:
 
 1920 by 1080 = ~ about 2 million purported pixels.  1280 by 720P equals
 about ~1 million pixels.  OK, fine.  One million pixels is about
 one-half the number of pixels as Two million pixels.  One is less than
 two.    >>

The Grand Alliance standard currently in place calls for 1080-line pictures
to be interlaced.  Since only half the lines are transmitted in each field
(in an interlaced TV system), the number of pixels per second is 1080/2 lines
X 1920 pixels per line X 60 fields per second = 62,208,000.

Note that the data rate does not change if the same information is sent
progressive instead of interlaced: 1080 lines X 1920 pixels per line X 30
frames per second still =
62,208,000.  

720 lines X 1280 pixels per line X 60 frames per second is 55,296,000 pixels
per second.  This is a difference of only 12.5%.

Regarding the costs associated with manufacturing digital TV sets, the only
thing that's absolutely necessary is the reception of the data.  How much of
it actually gets displayed is an entirely different matter, which in the
final analysis will be determined by how much you want to pay for a TV set.  

Interlace is a great thing in practical analog television systems, but it
simply becomes dead weight in digital ones.  Unfortunately, it's very hard to
convert interlaced to non-interlaced images without creating temporal
artifacts, so 1080i was included in the ATV standard to allow for a gradual
transition from present-day 525-line interlaced technology to DTV.
 Hopefully, after that transition has taken place, interlace will be seen as
useless old baggage and be discarded.

Cordially yours,
Christopher Bacon


---
  HDTV discussion thread is at http://www.alegria.com/telecine/hdtv.txt
         Thanks to Bill Topazio for support of the TIG in 1997
      TIG subscriber count is 862 on Thu Oct  9 09:51:56 PDT 1997
     mailinglist digest available.... unsubscribe via a message to
        'telecine-request at alegria.com' with Subject: unsubscribe


Follow-Ups: