vo_gpu: change --tone-mapping-desaturate algorithm

Comparing mpv's implementation against the ACES ODR reference samples
and algorithms, it seems like they're happy desaturating highlights
_way_ more aggressively than mpv currently does. And indeed, looking at
some example clips like The Redwoods (which is actually well-mastered),
the current desaturation produces unnatural-looking brightness fringes
where the sky meets the treeline.

Adjust the algorithm to make it apply to a much larger, more gradual
brightness region; and change the interpretation of the parameter. As a
bonus, the new parameter is actually sanely scaled (higher values = more
desaturation). Also, make it scale based on the signal level instead of
the luminance, to avoid under-desaturating bright blues.

1 files changed, 1 insertions, 1 deletions

diff --git a/video/out/gpu/video.c b/video/out/gpu/video.c
index 9191f062b6..eca74b4bb3 100644
--- a/video/out/gpu/video.c
+++ b/video/out/gpu/video.c
@@ -311,7 +311,7 @@ static const struct gl_video_opts gl_video_opts_def = {
     .gamma = 1.0f,
     .tone_mapping = TONE_MAPPING_MOBIUS,
     .tone_mapping_param = NAN,
-    .tone_mapping_desat = 2.0,
+    .tone_mapping_desat = 1.0,
     .early_flush = -1,
 };