vo_gpu_next: add --target-contrast-hdr option

Should be helpful for Windows ACM/macOS cases, which only use
target-contrast=auto might cause washed out colors.

Wayland shouldn't need this since we have #17345

Signed-off-by: Shengyu Qu <wiagn@4d2.org>

Author: Headcrabed

DOCS/man/options.rst

@@ -7509,6 +7509,22 @@ them.
     ``inf`` contrast specifies display with perfect black level, in practice OLED.
     (Only for ``--vo=gpu-next``)
 
+``--target-contrast-hdr=<no|auto|10-1000000|inf>``
+    Same as ``--target-contrast``, but only applies when ``--target-trc`` is set to
+    a HDR transfer function and would override the settings of ``--target-contrast``.
+    This allows to specify a different contrast for HDR content, This might be useful
+    when user is running a host OS that supports global color management and monitor
+    has large contrast ratio. In this case, with some GPU API and OS combinations,
+    mpv can't correctly get the actual contrast ratio info of the display when
+    ``--target-trc`` is a SDR transfer function, and only use
+    ``--target-contrast=auto`` might cause washed out colors.
+    ``no`` is the default value and means the contrast is only controlled by 
+    ``--target-contrast``.
+    ``auto`` means the contrast is infinite when HDR ``--target-trc`` is used, or
+    the contrast would be the value of actual monitor if available from host OS.
+    ``inf`` contrast specifies display with perfect black level, in practice OLED.
+    (Only for ``--vo=gpu-next``)
+
 ``--target-gamut=<value>``
     Constrains the gamut of the display. You can use this option to output e.g.
     DCIP3-in-BT.2020. Set ``--target-prim`` to the primaries of the containing

video/out/gpu/video.c

@@ -453,6 +453,8 @@ const struct m_sub_options gl_video_conf = {
             {"no", 0}, {"input", 1}, {"output", 2}, {"both", 1|2}, {"auto", 1|2|4})},
         {"target-contrast", OPT_CHOICE(target_contrast, {"auto", 0}, {"inf", -1}),
             M_RANGE(10, 10 / PL_COLOR_HDR_BLACK)},
+        {"target-contrast-hdr", OPT_CHOICE(target_contrast_hdr, {"no", 0}, {"auto", -1}, {"inf", -2}),
+            M_RANGE(10, 10 / PL_COLOR_HDR_BLACK)},
         {"target-gamut", OPT_STRING_VALIDATE(target_gamut, validate_target_gamut)},
         {"tone-mapping", OPT_CHOICE(tone_map.curve,
             {"auto",     TONE_MAPPING_AUTO},

video/out/gpu/video.h

@@ -142,6 +142,7 @@ struct gl_video_opts {
     int sdr_adjust_gamma;
     int treat_srgb_as_power22;
     int target_contrast;
+    int target_contrast_hdr;
     char *target_gamut;
     struct gl_tone_map_opts tone_map;
     bool correct_downscaling;

video/out/vo_gpu_next.c

@@ -915,6 +915,20 @@ static void update_options(struct vo *vo)
 static void apply_target_contrast(struct priv *p, struct pl_color_space *color, float min_luma)
 {
     const struct gl_video_opts *opts = p->opts_cache->opts;
+    const bool is_hdr = pl_color_space_is_hdr(color);
+
+    if (is_hdr && opts->target_contrast_hdr)
+        switch (opts->target_contrast_hdr) {
+            case -1:
+                color->hdr.min_luma = min_luma;
+                return;
+            case -2:
+                color->hdr.min_luma = 1e-7;
+                mp_assert(color->hdr.min_luma > 0);
+                return;
+            default:
+                goto apply_user_value;
+        }
 
     // Auto mode, use target value if available
     if (!opts->target_contrast) {
@@ -929,6 +943,7 @@ static void apply_target_contrast(struct priv *p, struct pl_color_space *color,
         return;
     }
 
+apply_user_value:
     // Infer max_luma for current pl_color_space
     pl_color_space_nominal_luma_ex(pl_nominal_luma_params(
         .color = color,
@@ -938,7 +953,10 @@ static void apply_target_contrast(struct priv *p, struct pl_color_space *color,
         .out_max = &color->hdr.max_luma
     ));
 
-    color->hdr.min_luma = color->hdr.max_luma / opts->target_contrast;
+    if (is_hdr && opts->target_contrast_hdr)
+        color->hdr.min_luma = color->hdr.max_luma / opts->target_contrast_hdr;
+    else
+        color->hdr.min_luma = color->hdr.max_luma / opts->target_contrast;
 }
 
 static void apply_target_options(struct priv *p, struct pl_frame *target,