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
<http://en.wikipedia.org/wiki/Color_space> in terms of one luminance
<http://en.wikipedia.org/wiki/Luminance_%28video%29> and two
chrominance <http://en.wikipedia.org/wiki/Chrominance> components. YUV
is used in the PAL <http://en.wikipedia.org/wiki/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 <http://en.wikipedia.org/wiki/RGB> model used in computer graphics
hardware, but not as closely as the HSL color space
<http://en.wikipedia.org/wiki/HSL_color_space> and HSV color space
<http://en.wikipedia.org/wiki/HSV_color_space>.
Y stands for the luminance
<http://en.wikipedia.org/wiki/Luminance_%28video%29> component (the
brightness) and U and V are the chrominance
<http://en.wikipedia.org/wiki/Chrominance> (color) components. The
YPbPr <http://en.wikipedia.org/wiki/YPbPr> color space used in analog
component video <http://en.wikipedia.org/wiki/Component_video> and its
digital child YCbCr <http://en.wikipedia.org/wiki/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 <http://en.wikipedia.org/wiki/YIQ>
color space used in the analog NTSC
<http://en.wikipedia.org/wiki/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