Jean Claude wrote:Interesting?
They come from where the 2 bits to go from 8 to 10 bits?
Salut Jean Claude,
It's not really that we "gain" 2 bits but more that we "loose" information by restricting the operations in a 8 bit space. Using bit depth as a measure for image quality is good -- up to a certain point. It's especially good to explain to the professional public. I'm sure better indicators are to be found in mathematics if ones really wants to maximize quality in its software.
If you want an example of what I'm talking about suppose you have a,b,c,d variables such as :
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a=0 ou 1 (1 bit)
b=0 ou 1 (1 bit)
c=a+b -> 0, 1 ou 2 (1.58 bits)
d=a-b -> -1, 0 ou 1 (1.58 bits)
To store "properly" (without loosing quality doing the reverse function) c and d you need more bits (4 bit because 2*log_2(3)=3.16 bits). But c and d "transport" only 2 bits of information (they are the result of a reversible function from a 2 bit space), the space of 4 bits will not always be used as its maximum as values are intertwined.
That's why I'm saying each step in a pipeline can lower quality and it's a huge mess. This was just an example, I'm not saying it actually happens in Premiere Pro or DaVinci Resolve