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Commit c795e7d0 authored by Hans Verkuil's avatar Hans Verkuil Committed by Mauro Carvalho Chehab
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media: media/doc: improve the SMPTE 2084 documentation 



Make note of the different luminance ranges between HDR and SDR.

Signed-off-by: default avatarHans Verkuil <hansverk@cisco.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@s-opensource.com>
parent fb98531e

Documentation/media/uapi/v4l/colorspaces-details.rst

+12 −0
Original line number Diff line number Diff line
@@ -793,3 +793,15 @@ Transfer function: 
Inverse Transfer function:

    L = (max(L':sup:`1/m2` - c1, 0) / (c2 - c3 *

    L'\ :sup:`1/m2`))\ :sup:`1/m1`



Take care when converting between this transfer function and non-HDR transfer

functions: the linear RGB values [0…1] of HDR content map to a luminance range

of 0 to 10000 cd/m\ :sup:`2` whereas the linear RGB values of non-HDR (aka

Standard Dynamic Range or SDR) map to a luminance range of 0 to 100 cd/m\ :sup:`2`.



To go from SDR to HDR you will have to divide L by 100 first. To go in the other

direction you will have to multiply L by 100. Of course, this clamps all

luminance values over 100 cd/m\ :sup:`2` to 100 cd/m\ :sup:`2`.



There are better methods, see e.g. :ref:`colimg` for more in-depth information

about this.