[opendtv] Re: News: CEA FORECASTS CONSUMER ELECTRONICS REVENUE WILL SURPASS $155 BILLION IN 2007
- From: "Dale Kelly" <dalekelly@xxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 10 Jan 2007 16:34:25 -0800
flyback1 wrote:
>Do you know what words U and V stand for and which component color value
each represents?
Sure, here's a reference copy for others edification, if interested.
UV simply uses a different RGB matrix but they are generally the same thing
as YIQ and are modulated/demodulated similarly in the two television system
(other than the phase reference signal). Actually, the YUV matrix seems more
useable to me but I don't know why RCA chose to use YIQ, any idea on your
end? Perhaps it was an IP thing?
Dale
The YUV model defines a color space in terms of one luminance and two
chrominance components. YUV is used in the PAL system of color encoding in
analog video, which is part of television standards in much of the world.
YUV models human perception of color more closely than the standard RGB
model used in computer graphics hardware, but not as closely as the HSL
color space and HSV color space.
Y stands for the luminance component (the brightness) and U and V are the
chrominance (color) components. The YPbPr color space used in analog
component video and its digital child YCbCr used in digital video are more
or less derived from it (Cb/Pb and Cr/Pr are deviations from grey on
blue-yellow and red-cyan axes whereas U and V are blue-luminance and
red-luminance differences), and are sometimes inaccurately called "YUV". The
YIQ color space used in the analog NTSC television broadcasting system is
related to it, although in a more complex way.
-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx]On
Behalf Of flyback1
Sent: Wednesday, January 10, 2007 4:00 PM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: News: CEA FORECASTS CONSUMER ELECTRONICS REVENUE
WILL SURPASS $155 BILLION IN 2007
Dale Kelly wrote:
flyback1 wrote:
>I started working in commercial broadcasting in 1967. I know what NTSC
looks like in the studio.
>I was in London in 1982 and 1984 and my firsthand observations were
that at that time the PAL
>television system displayed on sets in people's homes made better, more
detailed, more deeply
>saturated color pictures than I have ever seen in any NTSC studio
Yes, I've also been there and done that and do agree that the video is
superior. My point is that PAL does not define the number of scan lines nor
the video bandwidth, which are responsible for much of the superior picture
that we both observed.
I never said PAL defined the number of scan lines, and I know that PAL in
Brazil and a few other places has only 525 lines, just like NTSC.
When I said PAL, I meant the TV system in the UK that has always made
better looking pictures than NTSC, and almost as good pictures as ATSC.
PAL only defines the 180 degree alternating color reference phase shift
and the bandwidth available for the color signal, otherwise PAL and NTSC are
identical. PAL design accomplished two things:
1. It resolved color phase error problems and also made the Hue control
unnecessary. That was of more value in the early days but later broadcast
and receiver equipment improvements minimized it's value.
The first early 'Simple' PAL receivers didn't have a delay line to do
simultaneous decoding of the U and V color phases, so if you looked at the
screen with a magnifying glass you could see a field of B-Y and a field of
R-Y interlaced as alternating lines.
Do you know what words U and V stand for and which component color value
each represents?
Did you know that when RCA was inventing color in 1950, they tried an
alternating color field scheme? Their version was called CPA, Color Phase
Alternation, and Hazeltine's version of exactly the same idea was called
OCS, Oscillating Color Sequence.
These schemes were used with the early RCA 'color sampler' circuitry,
which was abandoned in favor of ??Philco's?? quadrature amplitude
modulation scheme.
2. PAL's two color subcarriers have equal bandwidth while NTSC has
different bandwidths for it's two color subcarriers ( I and Q). The Q
subcarrier transmits colors on the blue end of the visual spectrum where the
human eye perceives far less detail than it does at the Red/green end.
The Q subcarrier represents colors along the green-violet axis of the
vectorscope, and Plus I was chosen because it represents fleshtone. The
engineers at RCA felt there needed to be something readily identifiable in
the picture, so they made the I vector fall on the point of the vectorscope
where fleshtone is found.
Minus I represents cyan.
An NTSC picture missing the I modulation component looks far worse than
one missing Q.
Therefore NTSC designers reduced the bandwidth available to the Q signal
so as to its reduce cross talk into the video signal, but they did provide
full bandwidth for the more detailed I signal .
There were only two consumer TV sets that were built with full I & Q
demodulation, the very first Westinghouse color set [the very first set to
be introduced in 1954 beating RCA to the punch by ??a few weeks??] and the
very first RCA set, the CT-100.
No color sets built from 1955 on, until around the late 1980s had I & Q
demods.
I think also the only TV studio monitor that had I&Q demods was the RCA
round tube TM-21. Most NTSC TVsets were cheap and used narrowband X and Z
demods.
In reality, there should have been no noticeable difference between the
colors produced by the two systems (other than the phase issues).
On a 32 inch NTSC TV set, with FULL I & Q Demodulation all objects down to
about 1 inch in diameter will be reproduced in all three colors, R,B,G.
Objects between 1 inch and 3/16ths of an inch, will be reproduced only in
Orange and Cyan through the I demodulator, if the set really has one.
Objects in the picture less than 3/16ths of an inch in diameter will be
reproduced in B&W.
However, along came the receiver manufactures, who in their zeal to
minimize manufacturing costs, decided to filter both color signals at the
lower Q bandwidth and thereby saved the cost of a delay line (maybe a
dollar, if that). The receiver implementation is actually responsible for
the superior color detail seen in the PAL system.
I think someone at RCA was quoted as having said the use of narrowband
demodulation in their TV sets saved a lot of alignment headaches and one 1/2
watt resistor. This does not make sense to me because with narrowband demods
you only need one dalay line as you said, the second delay line being needed
to get the wider bandwidth I signal back in time with the slower, narrowband
Q.
I believe that the designers of PAL, who had the benefit of hind sight,
correctly made the decision to transmit equal color bandwidth to circumvent
the NTSC receiver manufacturing issue.
There is always a penalty for being first.
Someone else will come along later and improve on all your efforts without
having had to do the 99% of the inventing you did, and they will badmouth
you for not having done as good a job as they have.
Such is the penalty for being a pioneer, and paving the way and making it
easier and smoother for everything and everyone else that follows.
The NTSC Television System is still the most efficient in terms of
bandwith conservation and the best overall compromise design of all the
color systems in the world.
If you want to read a comprehensive Color Television History, go here:
http://novia.net/~ereitan
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