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[[Image:YIQ IQ plane.svg|thumb|300px|The YIQ color space at Y=0.5. Note that the I and Q chroma coordinates are scaled up to 1.0. See the formulae below in the article to get the right bounds.]]
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[[Image:YIQ components.jpg|right|thumb|An image along with its Y, I, and Q components.]]
 
'''YIQ''' is the [[color space]] used by the [[NTSC]] color TV system, employed mainly in [[North America|North]] and [[Central America]], and [[Japan]].
''I'' stands for ''in-phase'', while ''Q'' stands for ''quadrature'', referring to the components used in [[quadrature amplitude modulation]]. Some forms of NTSC now use the [[YUV]] color space, which is also used by other systems such as [[PAL]].
 
The Y component represents the [[Luminance (video)|luma]] information, and is the only component used by black-and-white television receivers. I and Q represent the [[chrominance]] information. In [[YUV]], the U and V components can be thought of as X and Y coordinates within the color space. I and Q can be thought of as a second pair of axes on the same graph, rotated 33°; therefore IQ and UV represent different coordinate systems on the same plane.
 
The YIQ system is intended to take advantage of human color-response characteristics. The eye is more sensitive to changes in the orange-blue (I) range than in the purple-green range (Q) &mdash; therefore less [[Bandwidth (signal processing)|bandwidth]] is required for Q than for I. Broadcast NTSC limits I to 1.3&nbsp;MHz and Q to 0.4&nbsp;MHz. I and Q are frequency interleaved into the 4&nbsp;MHz Y signal, which keeps the bandwidth of the overall signal down to 4.2&nbsp;MHz. In YUV systems, since U and V both contain information in the orange-blue range, both components must be given the same amount of bandwidth as I to achieve similar color fidelity.
 
Very few television sets perform true I and Q decoding, due to the high costs of such an implementation{{Citation needed|date=February 2007}}. Compared to the cheaper R-Y and B-Y decoding which requires only one filter, I and Q each requires a different filter to satisfy the bandwidth differences between I and Q.  These bandwidth differences also requires that the 'I' filter include a time delay to match the longer delay of the 'Q' filter.  The Rockwell Modular Digital Radio (MDR) was one I and Q decoding set, which in 1997 could operate in frame-at-a-time mode with a PC or in realtime with the Fast IQ Processor (FIQP). Some RCA "[[Colortrak]]" home TV receivers made circa 1985 not only used I/Q decoding, but also advertised its benefits along with its [[comb filter]]ing benefits as full "100 percent processing" to deliver more of the original color picture content. Earlier, more than one brand of color TV (RCA, Arvin) used I/Q decoding in the 1954 or 1955 model year on models utilizing screens about 13&nbsp;inches (measured diagonally). The original Advent projection television used I/Q decoding. Around 1990, at least one manufacturer (Ikegami) of professional studio picture monitors advertised I/Q decoding.
 
== Image processing ==
The YIQ representation is sometimes employed in color [[image processing]] transformations. For example, applying a [[histogram equalization]] directly to the channels in an RGB image would alter the [[color balance]] of the image. Instead, the histogram equalization is applied to the Y channel of the YIQ or YUV representation of the image, which only normalizes the brightness levels of the image.
 
== Formulas ==
These formulas approximate the conversion between the [[RGB]] color space and YIQ for a very popular non-FCC version of NTSC.
:<math>R, G, B, Y \in \left[ 0, 1 \right], \quad I \in \left[-0.5957, 0.5957\right], \quad Q \in \left[-0.5226, 0.5226\right]</math>
 
:<math>
\begin{bmatrix} Y \\ I \\ Q \end{bmatrix}
=
\begin{bmatrix}
  0.299    &  0.587    &  0.114 \\
  0.595716 & -0.274453 & -0.321263 \\
  0.211456 & -0.522591 &  0.311135
\end{bmatrix}
\begin{bmatrix} R \\ G \\ B \end{bmatrix}
</math>
 
:<math>
\begin{bmatrix} R \\ G \\ B \end{bmatrix}
=
\begin{bmatrix}
  1 &  0.9563 &  0.6210 \\
  1 & -0.2721 & -0.6474 \\
  1 & -1.1070 &  1.7046
\end{bmatrix}
\begin{bmatrix} Y \\ I \\ Q \end{bmatrix}
</math>
 
Two things to note regarding the RGB transformation matrix:
 
* The top row is identical to that of the [[YUV]] color space
* <math>\begin{bmatrix} R \\ G \\ B \end{bmatrix} = \begin{bmatrix} 1 \\ 1 \\ 1 \end{bmatrix} \implies \begin{bmatrix} Y \\ I \\ Q \end{bmatrix} = \begin{bmatrix} 1 \\ 0 \\ 0 \end{bmatrix}</math>
 
NOTE: The FCC version of NTSC, which is currently on the books for over-the-air analog color TV broadcasting, uses a slightly different matrix, which is:
 
"EQ′=0.41(EB′-EY′)+0.48(ER′-EY′).
EI′=-0.27(EB′-EY′)+0.74(ER′-EY′).
EY′=0.30ER′+0.59EG′+0.11EB′."
(Quoted from Code of Federal Regulations §73.682.)
 
== Phase-out ==
For broadcasting in the United States, it is currently in use only for low-power television stations, as full-power analog transmission was ended by the [[Federal Communications Commission]] (FCC) on 12 June 2009. It is still federally mandated for these transmissions as shown in this excerpt of the current FCC rules and regulations part 73 "TV transmission standard":
 
{{cquote|1=
The equivalent bandwidth assigned prior to modulation to the color difference signals ''EQ''′ and ''EI''′ are as follows:
 
Q-channel bandwidth:
At 400&nbsp;kHz less than 2&nbsp;dB down.
At 500&nbsp;kHz less than 6&nbsp;dB down.
At 600&nbsp;kHz at least 6&nbsp;dB down.
 
I-channel bandwidth:
At 1.3&nbsp;MHz less than 2&nbsp;dB down.
At 3.6&nbsp;MHz at least 20&nbsp;dB down.
}}
 
==References==
*Buchsbaum, Walter H. ''Color TV Servicing, third edition''. Englewood Cliffs, NJ: Prentice Hall, 1975. ISBN 0-13-152397-X
 
== External links ==
* [http://www.cs.rit.edu/~ncs/color/a_spaces.html Demonstrative color conversion applet]
 
{{Color space}}
 
{{DEFAULTSORT:Yiq}}
[[Category:Color space]]

Latest revision as of 12:37, 12 January 2015

A lagging computer is absolutely annoying and is quite a headache. Almost every individual that utilizes a computer faces this problem several time or the different. If the computer equally suffers from the same issue, there are it difficult to continue working as normal. In such a situation, the thought, "what should I do to create my PC run quicker?" is recurring plus infuriating. There's a solution, though!

If you registry gets cluttered up with a lot of junk we don't use, the PC may run slower. Therefore it's prudent which you regularly get a registry cleaned.

One of the most overlooked factors a computer usually slow down is considering the registry has become corrupt. The registry is essentially your computer's operating system. Anytime you're running a computer, entries are being made and deleted from the registry. The impact this has is it leaves false entries inside a registry. So, your computer's resources should function about these false entries.

Always see to it which you have installed antivirus, anti-spyware plus anti-adware programs plus have them updated on a regular basis. This can help stop windows XP running slow.

So to fix this, we only have to be capable to create all of the registry files non-corrupted again. This might dramatically speed up the loading time of the computer and will allow we to a big number of things on it again. And fixing these files couldn't be easier - you only require to employ a tool called a tuneup utilities.

Let's begin with all the bad sides initially. The initial cost of the product is truly inexpensive. But, it only comes with 1 year of updates. After which you need to subscribe to monthly updates. The advantage of which is the fact that ideal optimizer has enough money plus resources to analysis errors. This way, you may be ensured of safe fixes.

The disk requires area inside order to run smoothly. By freeing up some space from the disk, you'll be capable to speed up the PC a bit. Delete all file inside the temporary internet files folder, recycle bin, well-defined shortcuts plus icons from your desktop that we never utilize and remove programs we never use.

Another important system you'll like to receive is a registry cleaner. The registry is a big list of everything installed on a computer, and Windows references it whenever it opens a program or uses a device attached to your computer. Whenever you delete a program, its registry entry should moreover be deleted, however, often it's not. A registry cleaner can receive rid of these older entries thus Windows may search the registry faster. It also deletes or corrects any entries that viruses have corrupted.

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