Encoding
Two encodings are defined for the individual primaries: a linear 16 bit per channel encoding and a nonlinear 12 bit per channel encoding.
The 16 bit scRGB(16) encoding is the linear RGB channels converted by . Compared to 8-bit sRGB this ranges from about 1/2 the color resolution near 0.0 to more than 10 times the color resolution near 1.0. Storage as 16 bits clamps the linear range to .
The 12-bit scRGB-nl encoding is the linear RGB channels passed through the same gamma function as sRGB (for negative numbers use -f(-x)) and then converted by . This is exactly 5 times the color resolution of 8-bit sRGB, and 8-bit sRGB can be converted directly with . The linear range is clamped to the slightly larger
A 12-bit encoding called scYCC-nl is the conversion of the non-linear sRGB levels to JFIF-Y'CbCr and then converted by and . This form can allow greater compression and direct conversion to/from JPEG files and video hardware.
With the addition of an alpha channel with the same number of bits the 16-bit encoding may be seen referred to as 64 bit and the 12-bit encoding referred to as 48-bit. Alpha is not encoded as above, however. Alpha is instead a linear 0-1 range multiplied by where is 12 or 16.
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