[opendtv] Re: Frames Per Second of 720P

  • From: "Martin Holmes" <Martin.Holmes@xxxxxxxxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Wed, 23 Jul 2008 15:59:29 +0100

Good thing we won't use this nomenclature then ;-)

Using frame rate as an expression makes good technical sense.  Using 60
arbitrarily does not when it's actually 59.94.

Forget legacy black and white NTSC for a second.  Only one HD system
used true 60 interlace; MUSE in Japan.

In the (NTSC) television industry we don't use 30 or 24 either.  It's 29
and 23 (ignoring all the extra .94's and .97 and .976's).  In HD it
would be expressed (clearly, and without any doubt as to picture count
expectations) as;

720 @ 59 p
1080 @ 29 i
1080 @ 23 pSf
486 @ 29 i

720 @ 50 p
1080 @ 25 i
1080 @ 25 pSf
576 @ 25 i

I completely agree that the industry needs to move away from interlace.
For the first time, the consumer marketplace has completely outstripped
the professional industry in terms of the image quality than can be seen
at home.  

This is the real debate that we need to have in this environment in my
opinion.  NTSC worked for us for 60 years, ATSC is only 12 years old or
so and it's obsolete (for many reasons).  If we need another
transmission standard it will take at least 10 years of discussion from
the day it's started and I don't think it's the answer.  

1080 @ 59 p now there is an HD system we could use today.

My best, MH.



-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx]
On Behalf Of Craig Birkmaier
Sent: Tuesday, July 22, 2008 6:57 AM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: Frames Per Second of 720P

At 4:48 PM -0400 7/18/08, Manfredi, Albert E wrote:
>John Shutt wrote:
>
>>  This is exactly why I don't understand the nomenclature that
>>  seemed to only come into fashion with the advent of HD, of
>>  calling 1920x1080 thirty frames per second interlaced as "i60"
>
>Two points:
>
>1. ATSC documentation always says i30.
>
>2. So, am I to conclude that 50+ years ago, 525/60 meant 60 frames per
>second?
>

You might conclude this, but you would be wrong.

Before NTSC color we did have a true 60 field per second TV system, 
which change to 59.94 when NTSC color was added.

I believe the TV world is finally ready to admit that interlace 
sucks, but the legacy will be with us for many years to come.

The real travesty here is that the nomenclature for interlaced 
formats suggests that there is far more vertical resolution than is 
actually present. With field based systems we Do get the advantage of 
the higher temporal update rate (60/59.94), but at half the vertical 
resolution. The interlace pundits will tell you that you get more 
than half; they will talk about Kell factors and interlace factors, 
and say that you get 60 to 70% of the effective vertical detail of a 
frame based system.

But you also get interlace artifacts, and difficulties with encoding 
the color difference signals using frame based codecs like MPEG-2 (- 
yes I know that there are MPEG-2 tools for encoding interlace, but 
they also suck.

In my book, the the correct nomenclature for an interlaced 1080 line 
format should be:

1920 x 540 @ 60/59.94i

Regards
Craig
 
 
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