vo_gpu_next: add --linearize-srgb-as-power22

The sRGB EOTF is a pure gamma 2.2 function. There is some disagreement
regarding the sRGB specification and whether it should be treated as a
piecewise function. Many displays are actually gamma 2.2, and content
mastered for PC is typically affected by that. Therefore, linearize it
as such to avoid raised blacks.

See:
IEC 61966-2-1-1999
https://community.acescentral.com/t/srgb-piece-wise-eotf-vs-pure-gamma/4024
KhronosGroup/DataFormat#19
https://gitlab.freedesktop.org/pq/color-and-hdr/-/issues/12
https://github.com/dylanraga/win11hdr-srgb-to-gamma2.2-icm

Author: kasper93

DOCS/man/options.rst

@@ -7354,6 +7354,19 @@ them.
         transfer function is SDR. This way you can control SDR output separately
         from HDR output.
 
+``--linearize-srgb-as-power22``
+    When enabled, sRGB is linearized using a pure gamma 2.2 function, instead of
+    the sRGB piecewise function. There is some disagreement regarding the sRGB
+    specification and whether it should be treated as a piecewise function.
+    Many displays are actually gamma 2.2, and content mastered for PC is typically
+    affected by that. Disabled by default. (Only for ``--vo=gpu-next``)
+
+    See for more details:
+    https://community.acescentral.com/t/srgb-piece-wise-eotf-vs-pure-gamma/4024
+    https://github.com/KhronosGroup/DataFormat/issues/19
+    https://gitlab.freedesktop.org/pq/color-and-hdr/-/issues/12
+    https://github.com/dylanraga/win11hdr-srgb-to-gamma2.2-icm
+
 ``--tone-mapping=<value>``
     Specifies the algorithm used for tone-mapping images onto the target
     display. This is relevant for both HDR->SDR conversion as well as gamut

video/out/gpu/video.c

@@ -445,6 +445,7 @@ 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)},
+        {"linearize-srgb-as-power22", OPT_BOOL(linearize_srgb_as_power22)},
         {"target-contrast", OPT_CHOICE(target_contrast, {"auto", 0}, {"inf", -1}),
             M_RANGE(10, 1000000)},
         {"target-gamut", OPT_CHOICE_C(target_gamut, pl_csp_prim_names)},

video/out/gpu/video.h

@@ -139,6 +139,7 @@ struct gl_video_opts {
     int target_trc;
     int target_peak;
     int hdr_reference_white;
+    bool linearize_srgb_as_power22;
     int target_contrast;
     int target_gamut;
     struct gl_tone_map_opts tone_map;

video/out/vo_gpu_next.c

@@ -675,6 +675,21 @@ static bool map_frame(pl_gpu gpu, pl_tex *tex, const struct pl_source_frame *src
     if (opts->hdr_reference_white && !pl_color_transfer_is_hdr(frame->color.transfer))
         frame->color.hdr.max_luma = opts->hdr_reference_white;
 
+    if (opts->linearize_srgb_as_power22 && frame->color.transfer == PL_COLOR_TRC_SRGB) {
+        // The sRGB EOTF is a pure gamma 2.2 function. There is some disagreement
+        // regarding the sRGB specification and whether it should be treated
+        // as a piecewise function. Many displays are actually gamma 2.2, and content
+        // mastered for PC is typically affected by that. Therefore, linearize it
+        // as such to avoid raised blacks.
+        // See:
+        // IEC 61966-2-1-1999
+        // <https://community.acescentral.com/t/srgb-piece-wise-eotf-vs-pure-gamma/4024>
+        // <https://github.com/KhronosGroup/DataFormat/issues/19>
+        // <https://gitlab.freedesktop.org/pq/color-and-hdr/-/issues/12>
+        // <https://github.com/dylanraga/win11hdr-srgb-to-gamma2.2-icm>
+        frame->color.transfer = PL_COLOR_TRC_GAMMA22;
+    }
+
     if (fp->hwdec) {
 
         struct mp_imgfmt_desc desc = mp_imgfmt_get_desc(par.imgfmt);