[FFmpeg-user] Does converting to yuv444p by default make sense?

thljcl jiachielee at live.com
Thu Aug 1 15:20:43 CEST 2013

```No, you haven’t.
“Think of a Y value of 0. Cb and Cr can have 256x256=65536 different
combination of values, but they all represent the same black color in RGB:
0,0,0”
This argument is wrong. Plain and simple.
First of all, I do not know what “Y=0” would represent. It is not
necessarily black. Each color in YCbCr is represented by three numbers. I
think you got this idea because of you think of “Y” as luma component, if
there is ‘no’ luma information, it must be black, right? That is the
misunderstanding. As a matter of fact, I explicitly told you that you only
know which three numbers from YCbCr represent from a well-defined mapping
from an absolute color space.
By the way, “Y” is called luma component not for the reason you think it is.
That is, for grayscale image, both Cr and Cr would represented by two unique
but maybe different numbers, only “Y” component is allowed to have different
numbers, which is 256 in total. That would be 256×1×1=256.
No, I do not claim that we can know which color YCbCr represents without
mapping. It’s just that YCbCr affine mapping (of different conversion
standards) is defined specifically to behave in such manner.
To answer your question directly, if Cb and Cr changes but Y remains
unchanged, there would be different colors, not “black” as you claimed; and
I don’t even suggest “Y=0” leads to black.
In short, yes, in 24-bit YCbCr, there would be exactly 16,777,216 number of
colors

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