http://en.wikipedia.org/wiki/YUV
"The YPbPr color model used in analog component video and its digital version
YCbCr used in digital video are more or less derived from it, and are sometimes
called Y'UV. (CB/PB and CR/PRare deviations from grey on blue–yellow and
red–cyan axes, whereas U and V are blue–luminance and red–luminance
differences.) The Y'IQ color space used in the analog NTSC television
broadcasting system is related to it, although in a more complex way."
________________________________
From: Thiago Macieira <[email protected]>
To: [email protected]
Sent: Friday, March 14, 2014 12:22 PM
Subject: Re: [Interest] QVideoFrame and YUV question
Em sex 14 mar 2014, às 08:47:15, Jason H escreveu:
> The frame is not laid out like RGB. This is for legacy reasons. Black and
> White TV presented a black and white frame (Y) when color TV was added, it
> was added in a backwards-compatible way
This has nothing to do with black & white TV. Digital image formats were
invented way after colour TV.
The reason why Y is sampled per pixel whereas U and V aren't is because the
eye isn't as sensitive to colour as it is to luminosity. By using one U and
one V for 4 pixels, we reduce the amount of data from 12 values to 6 in each
2x2 block -- that is, half the amount of data.
There are some other YUV formats that lay out data differently, including all
the chrominance values, like YUV 4:4:4.
--
Thiago Macieira - thiago.macieira (AT) intel.com
Software Architect - Intel Open Source Technology Center
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