From c2d4fd0ef43e44c5c8caee13ae486ae05784c3a5 Mon Sep 17 00:00:00 2001 From: Niklas Haas Date: Wed, 25 Oct 2017 17:05:52 +0200 Subject: 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. --- DOCS/man/options.rst | 17 +++++++++-------- video/out/gpu/video.c | 2 +- video/out/gpu/video_shaders.c | 18 ++++++++++-------- 3 files changed, 20 insertions(+), 17 deletions(-) diff --git a/DOCS/man/options.rst b/DOCS/man/options.rst index 6d1ff4df5a..5c4882883a 100644 --- a/DOCS/man/options.rst +++ b/DOCS/man/options.rst @@ -4896,14 +4896,15 @@ The following video options are currently all specific to ``--vo=gpu`` and some drivers, so enable at your own risk. ``--tone-mapping-desaturate=`` - Apply desaturation for highlights that exceed this level of brightness. The - higher the parameter, the more color information will be preserved. This - setting helps prevent unnaturally blown-out colors for super-highlights, by - (smoothly) turning into white instead. This makes images feel more natural, - at the cost of reducing information about out-of-range colors. - - The default of 2.0 is somewhat conservative and will mostly just apply to - skies or directly sunlit surfaces. A setting of 0.0 disables this option. + Apply desaturation for highlights. The parameter essentially controls the + steepness of the desaturation curve. The higher the parameter, the more + aggressively colors will be desaturated. This setting helps prevent + unnaturally blown-out colors for super-highlights, by (smoothly) turning + into white instead. This makes images feel more natural, at the cost of + reducing information about out-of-range colors. + + The default of 1.0 provides a good balance that roughly matches the look + and feel of the ACES ODT curves. A setting of 0.0 disables this option. ``--gamut-warning`` If enabled, mpv will mark all clipped/out-of-gamut pixels that exceed a 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, }; diff --git a/video/out/gpu/video_shaders.c b/video/out/gpu/video_shaders.c index eb629a13ca..7081a10fef 100644 --- a/video/out/gpu/video_shaders.c +++ b/video/out/gpu/video_shaders.c @@ -565,18 +565,19 @@ static void pass_tone_map(struct gl_shader_cache *sc, float ref_peak, { GLSLF("// HDR tone mapping\n"); - // Desaturate the color using a coefficient dependent on the luminance - GLSL(float luma = dot(dst_luma, color.rgb);) - if (desat > 0) { - GLSLF("float overbright = max(luma - %f, 1e-6) / max(luma, 1e-6);\n", desat); - GLSL(color.rgb = mix(color.rgb, vec3(luma), overbright);) - } - // To prevent discoloration due to out-of-bounds clipping, we need to make // sure to reduce the value range as far as necessary to keep the entire // signal in range, so tone map based on the brightest component. GLSL(float sig = max(max(color.r, color.g), color.b);) - GLSL(float sig_orig = sig;) + + // Desaturate the color using a coefficient dependent on the signal + if (desat > 0) { + GLSL(float luma = dot(dst_luma, color.rgb);) + GLSL(float coeff = max(sig - 0.18, 1e-6) / max(sig, 1e-6);); + GLSLF("coeff = pow(coeff, %f);\n", 10.0 / desat); + GLSL(color.rgb = mix(color.rgb, vec3(luma), coeff);) + GLSL(sig = mix(sig, luma, coeff);) // also make sure to update `sig` + } if (!ref_peak) { // For performance, we want to do as few atomic operations on global @@ -612,6 +613,7 @@ static void pass_tone_map(struct gl_shader_cache *sc, float ref_peak, GLSLHF("const float sig_peak = %f;\n", ref_peak); } + GLSL(float sig_orig = sig;) switch (algo) { case TONE_MAPPING_CLIP: GLSLF("sig = %f * sig;\n", isnan(param) ? 1.0 : param); -- cgit v1.2.3