Talk:YIQ

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These formulae are a bit much for the main article (and poorly presented), thus removed:

The approximate value of the matrix is:

\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} \cdot \begin{bmatrix}R\\G\\B\end{bmatrix}

The exact value of the formula is:

Y  = + 0.299R + 0.587G + 0.114B
I  = + 0.877(R - Y) cos 33 - 0.492(B - Y) sin 33 = + [(0.877 cos 33)(1 - 0.299) - (0.492 sin 33)(-0.299)]R + [(0.877 cos 33)(-0.587) - (0.492 sin 33)(-0.587)]G + [(0.877 cos 33)(-0.114) - (0.492 sin 33)(1 - 0.114)]B
Q  = + 0.877(R - Y) sin 33 + 0.492(B - Y) cos 33 = + [(0.877 sin 33)(1 - 0.299) + (0.492 cos 33)(-0.299)]R + [(0.877 sin 33)(-0.587) + (0.492 cos 33)(-0.587)]G + [(0.877 sin 33)(-0.114) + (0.492 cos 33)(1 - 0.114)]B

The exact value of the matrix is:

\begin{bmatrix}+0.299&+0.587&+0.114\\((0.877 cos 33)(1 - 0.299) - (0.492 sin 33)(-0.299))&((0.877 cos 33)(-0.587) - (0.492 sin 33)(-0.587))&((0.877 cos 33)(-0.114) - (0.492 sin 33)(1 - 0.114))\\((0.877 sin 33)(1 - 0.299) + (0.492 cos 33)(-0.299))&((0.877 sin 33)(-0.587) + (0.492 cos 33)(-0.587))&((0.877 sin 33)(-0.114) + (0.492 cos 33)(1 - 0.114))\end{bmatrix}

The approximate value of the inverse matrix is:

\begin{bmatrix}1&1.176&0.764\\1&-0.411&-0.678\\1&-0.965&1.486\end{bmatrix}

The exact value of the inverse matrix is:

\begin{bmatrix}1&\frac{701}{500}\cos 33^\circ&\frac{701}{500}\sin 33^\circ\\1&\frac{101004\sin 33^\circ-209599\cos 33^\circ}{293500}&-\frac{101004\cos 33^\circ+209599\sin 33^\circ}{293500}\\1&-\frac{443}{250}\sin 33^\circ&\frac{443}{250}\cos 33^\circ\end{bmatrix}

--Dtcdthingy 07:30, 27 Nov 2004 (UTC)

Actually, the exact value of the inverse matrix is:
\begin{bmatrix} +0.299 & +0.587 & +0.114 \\ ((0.877\cos 33)(1 - 0.299) - (0.492\sin 33)(-0.299)) & ((0.877\cos 33)(-0.587) - (0.492\sin 33)(-0.587)) & ((0.877\cos 33)(-0.114) - (0.492\sin 33)(1 - 0.114)) \\ ((0.877\sin 33)(1 - 0.299) + (0.492\cos 33)(-0.299)) & ((0.877\sin 33)(-0.587) + (0.492\cos 33)(-0.587)) & ((0.877\sin 33)(-0.114) + (0.492\cos 33)(1 - 0.114)) \end{bmatrix}^{-1}
= \begin{bmatrix} 1 & \frac{1000}{877}\cdot\frac{\cos 33}{\cos 33^2+\sin 33^2} & \frac{1000}{877}\cdot\frac{\sin 33}{\cos 33^2+\sin 33^2} \\ 1 & \frac{500}{21106759}\cdot\frac{16663\sin 33-24518\cos 33}{\cos 33^2+\sin 33^2} & \frac{-500}{21106759}\cdot\frac{16663\cos 33+24518\sin 33}{\cos 33^2+\sin 33^2} \\ 1 & \frac{250}{123}\cdot\frac{\sin 33}{\cos 33^2+\sin 33^2} & \frac{250}{123}\cdot\frac{\cos 33}{\cos 33^2+\sin 33^2} \end{bmatrix} = \begin{bmatrix} 1 & \frac{1000}{877}\cos 33 & \frac{1000}{877}\sin 33 \\ 1 & \frac{8331500\sin 33-12259000\cos 33}{21106759} & -\frac{8331500\cos 33+12259000\sin 33}{21106759} \\ 1 & -\frac{1000}{492}\sin 33 & \frac{1000}{492}\cos 33 \end{bmatrix} = \begin{bmatrix} 1 & \frac{1000}{877}\cos 33 & \frac{1000}{877}\sin 33 \\ 1 & \frac{9500}{24067}\sin 33-\frac{299000}{514799}\cos 33 & -\frac{9500}{24067}\cos 33-\frac{299000}{514799}\sin 33 \\ 1 & -\frac{250}{123}\sin 33 & \frac{250}{123}\cos 33 \end{bmatrix}
= \begin{bmatrix} 1 & 0.9562948323208939905 & 0.6210251254447287141 \\ 1 & -0.2721214740839773195 & -0.6473809535176157222 \\ 1 & -1.106989908567128216 & 1.704614975498829329 \end{bmatrix}
--Zom-B 04:36, 9 Sep 2006 (UTC)
  • This uses a surreal amount of precision: 19 significant figures for a formula presented as approximate! I don't have the expertise to say how many figures are justified from these inputs, but I have cropped it down to 4 decimal places. I suspect 3 would be better. Notinasnaid 19:48, 21 March 2007 (UTC)

[edit] Crappy ntsc

is the information reduction used with YIQ the reason why ntsc video pictures look sort of trashy and blurry compared to the pal video system YUV? --Abdull 12:42, 23 Mar 2005 (UTC)

NTSC is only about 485 visible lines tall. If you round that down and use square pixels, it's 640x480. (familiar?) PAL is about 576 visible lines tall, and thus about 768x576 if you assume square pixels. This doesn't come free though; PAL is 50 fields (25 frames) per second while NTSC is 59.94 fields (29.97 frames) per second. PAL is jittery compared to NTSC. Even with the low framerate, PAL generally takes more bandwidth on the air. (it's a radio spectrum hog) AlbertCahalan 03:51, 23 May 2005 (UTC)
Because of the "485 visible lines" mentioned above, some square pixel calculations cited a figure of 648x486. –Wbwn 02:10, 6 September 2006 (UTC)
PAL allocates more bandwidth for color information (1.3MHz each for U and V) than NTSC (0.5MHz and 1.3MHz for I and Q). The PAL system also cancels out the color error that ends up right on the screen in NTSC. There's also much more luma bandwidth (6MHz vs 4.3 MHz). Combined with the lower frame rate, this allows much more detail to be present in each frame. --Dtcdthingy 20:03, 24 May 2005 (UTC)
Do the above ideas fit the topic of YIQ space? —The preceding unsigned comment was added by Scetpfe (talk • contribs) 03:21, 24 February 2007 (UTC).

[edit] Anyone?

Does anyone understand this subject enough to clean it up? It's been marked since april last year.

I changed it to {{expert}} to see if that'll attract anyone. 68.39.174.238 02:45, 14 April 2006 (UTC)

I have some minor expertise in this subject and I believe this article offers a good explaination of the subject.

Two technical statements in the article concerned me. Both were added by Mako098765.

The first was that the I and Q components refer to the "modulation schemes used" but they don't really they refer to the in-phase and quadrature-phase "components used in quadrature amplitude modulation".

The second was his explaination of the image. The origin he gave was not even on the diagram presented and he seemed to assume the I and Q components are polar co-ordinates when actually they are typically cartesian co-ordinates.

I have fixed both these problems, though this involved removing the image.

My only other concern was that the article was a little light in discussing how the YIQ colour space is used in image processing.

That said this article really does offer a good explaination of the topic, so I am removing the expert tag unless another expert offers a differing opinion.

Cedars 02:50, 18 May 2006 (UTC)

I got my info from the Buchsbaum TV servicing book that I mentioned. The color space diagram explanation may be somewhat suspect, but I am fairly confident about the modulation aspect, which refers to broadcast NTSC. From your comments about coordinates and image processing, you bring to mind YUV. - mako 06:09, 19 May 2006 (UTC)

[edit] Move page

I suggest that this article, as well as the YUV and YDbDr articles, be renamed so that the words "color space" or "color model" occur afterward. This way they adhere to the convention set by the other color space articles. -SharkD 02:13, 21 October 2006 (UTC)

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