vo_opengl: implement HDR (SMPTE ST2084)

Currently, this relies on the user manually entering their display
brightness (since we have no way to detect this at runtime or from ICC
metadata). The default value of 250 was picked by looking at ~10 reviews
on tftcentral.co.uk and realizing they all come with around 250 cd/m^2
out of the box. (In addition, ITU-R Rec. BT.2022 supports this)

Since there is no metadata in FFmpeg to indicate usage of this TRC, the
only way to actually play HDR content currently is to set
``--vf=format=gamma=st2084``. (It could be guessed based on SEI, but
this is not implemented yet)

Incidentally, since SEI is ignored, it's currently assumed that all
content is scaled to 10,000 cd/m^2 (and hard-clipped where out of
range). I don't see this assumption changing much, though.

As an unfortunate consequence of the fact that we don't know the display
brightness, mixed with the fact that LittleCMS' parametric tone curves
are not flexible enough to support PQ, we have to build the 3DLUT
against gamma 2.2 if it's used. This might be a good thing, though,
consdering the PQ source space is probably not fantastic for
interpolation either way.

Partially addresses #2572.

1 files changed, 1 insertions, 0 deletions

diff --git a/video/csputils.h b/video/csputils.h
index 1d8d3b1d14..19dd88f145 100644
--- a/video/csputils.h
+++ b/video/csputils.h
@@ -78,6 +78,7 @@ enum mp_csp_trc {
     MP_CSP_TRC_GAMMA22,
     MP_CSP_TRC_GAMMA28,
     MP_CSP_TRC_PRO_PHOTO,
+    MP_CSP_TRC_SMPTE_ST2084,
     MP_CSP_TRC_COUNT
 };