vo_opengl: refactor HDR mechanism

Instead of doing HDR tone mapping on an ad-hoc basis inside
pass_colormanage, the reference peak of an image is now part of the
image params (alongside colorspace, gamma, etc.) and tone mapping is
done whenever peak_src != peak_dst.

To get sensible behavior when mixing HDR and SDR content and displays,
target-brightness is a generic filler for "the assumed brightness of SDR
content".

This gets rid of the weird display_scaled hack, sets the framework
for multiple HDR functions with difference reference peaks, and allows
us to (in a future commit) autodetect the right source peak from
the HDR metadata.

(Apart from metadata, the source peak can also be controlled via
vf_format. For HDR content this adjusts the overall image brightness,
for SDR content it's like simulating a different exposure)

1 files changed, 8 insertions, 0 deletions

diff --git a/DOCS/man/vf.rst b/DOCS/man/vf.rst
index 40c499cb5a..b4e4438f78 100644
--- a/DOCS/man/vf.rst
+++ b/DOCS/man/vf.rst
@@ -312,6 +312,14 @@ Available filters are:
        :prophoto:     ProPhoto RGB (ROMM) curve
        :st2084:       SMPTE ST2084 (HDR) curve
 
+    ``<peak>``
+        Reference peak illumination for the video file. This is mostly
+        interesting for HDR, but it can also be used tone map SDR content
+        to a darker or brighter exposure.
+
+        The default of 0.0 will default to the display's reference brightness
+        for SDR and the source's reference brightness for HDR.
+
     ``<stereo-in>``
         Set the stereo mode the video is assumed to be encoded in. Takes the
         same values as the ``--video-stereo-mode`` option.