video/out/gpu/video: add --sdr-adjust-gamma

Author: kasper93

DOCS/interface-changes/treat-srgb-as-power22.txt

@@ -1 +1,2 @@
 add `--treat-srgb-as-power22`
+add `--sdr-adjust-gamma`

DOCS/man/options.rst

@@ -7354,6 +7354,36 @@ them.
         transfer function is SDR. This way you can control SDR output separately
         from HDR output.
 
+``--sdr-adjust-gamma=<auto|yes|no>``
+    SDR transfer functions are often ambiguous or mismatched. Even if files are
+    tagged with a specific function (e.g. ``bt.709``), the actual content may
+    not match. For example, most screen capture software tags its output as
+    ``bt.709``, but the content is usually a direct sRGB capture.
+
+    On the target side, "sRGB" is also ambiguous, some displays are factory
+    calibrated to a pure power 2.2 gamma, while others may use the sRGB
+    piecewise curve. Both of which are typically configured as "sRGB" in the
+    swapchain configuration. Similar inconsistencies exist across compositor
+    implementations of color management, as different platforms handle this in
+    different ways. See also ``--treat-srgb-as-power22``.
+    Additionally, ``bt.1886`` requires display contrast ratio to be known for
+    correct rendering, which is often unavailable. Use``--target-contrast`` to
+    specify it.
+
+    This option controls whether SDR content should have its gamma adjusted.
+    It only applies to the "sRGB" swapchain target configuration, since that is
+    the most common and ambiguous case. If set to ``no``, content tagged as
+    ``sRGB``, ``gamma2.2`` or ``bt.1886`` will be rendered as-is. If set to
+    ``yes``, it will be converted based on the available metadata.
+
+    ``auto`` (default) behaves like ``no``, except when ``--target-trc`` is
+    explicitly set, in which case it behaves like ``yes``.
+
+    Generally it's recommended to enable this option, if you can ensure that
+    both source and target metadata is correct.
+
+    (Only for ``--vo=gpu-next``)
+
 ``--treat-srgb-as-power22=<no|input|output|both|auto>``
     When enabled, sRGB is (de)linearized using a pure power 2.2 curve instead of
     the standard sRGB piecewise transfer function.

video/out/gpu/video.c

@@ -446,6 +446,8 @@ const struct m_sub_options gl_video_conf = {
             M_RANGE(10, 10000)},
         {"hdr-reference-white", OPT_CHOICE(hdr_reference_white, {"auto", 0}),
             M_RANGE(10, 10000)},
+        {"sdr-adjust-gamma", OPT_CHOICE(sdr_adjust_gamma,
+            {"auto", 0}, {"yes", 1}, {"no", -1})},
         {"treat-srgb-as-power22", OPT_CHOICE(treat_srgb_as_power22,
             {"no", 0}, {"input", 1}, {"output", 2}, {"both", 1|2}, {"auto", 1|2|4})},
         {"target-contrast", OPT_CHOICE(target_contrast, {"auto", 0}, {"inf", -1}),

video/out/gpu/video.h

@@ -139,6 +139,7 @@ struct gl_video_opts {
     int target_trc;
     int target_peak;
     int hdr_reference_white;
+    int sdr_adjust_gamma;
     int treat_srgb_as_power22;
     int target_contrast;
     int target_gamut;

video/out/vo_gpu_next.c

@@ -1253,6 +1253,17 @@ static bool draw_frame(struct vo *vo, struct vo_frame *frame)
     pl_frame_from_swapchain(&target, &swframe);
     bool strict_sw_params = target_hint && !pass_colorspace && p->next_opts->target_hint_strict;
     apply_target_options(p, &target, hint.hdr.min_luma, strict_sw_params);
+    if (target.color.transfer == PL_COLOR_TRC_SRGB && frame->current &&
+        ((opts->sdr_adjust_gamma == 0 && opts->target_trc == PL_COLOR_TRC_UNKNOWN) ||
+         opts->sdr_adjust_gamma == -1))
+    {
+        switch (frame->current->params.color.transfer) {
+        case PL_COLOR_TRC_BT_1886:
+        case PL_COLOR_TRC_GAMMA22:
+        case PL_COLOR_TRC_SRGB:
+            target.color.transfer = frame->current->params.color.transfer;
+        }
+    }
     if (target.color.transfer == PL_COLOR_TRC_SRGB) {
         // sRGB reference display is pure 2.2 power function, see IEC 61966-2-1-1999.
         if (opts->treat_srgb_as_power22 & 2)