[vlc-commits] direct3d11: fix HLG displaying on LDR displays

[Steve Lhomme]

vlc | branch: master | Steve Lhomme <robUx4 at videolabs.io> | Tue Mar  7 16:39:07 2017 +0100| [130348dea55d5b4c7ee3eead169cf19c947b6282] | committer: Jean-Baptiste Kempf

direct3d11: fix HLG displaying on LDR displays

Signed-off-by: Jean-Baptiste Kempf <jb at videolan.org>

> http://git.videolan.org/gitweb.cgi/vlc.git/?a=commit;h=130348dea55d5b4c7ee3eead169cf19c947b6282
---

 modules/video_output/win32/direct3d11.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/modules/video_output/win32/direct3d11.c b/modules/video_output/win32/direct3d11.c
index 9fafc53..fb62286 100644
--- a/modules/video_output/win32/direct3d11.c
+++ b/modules/video_output/win32/direct3d11.c
@@ -313,6 +313,19 @@ static const char* globPixelShaderDefault = "\
       return x;\
   }\
   \
+  /* https://en.wikipedia.org/wiki/Hybrid_Log-Gamma#Technical_details */\
+  inline float inverse_HLG(float x){\
+      const float B67_a = 0.17883277;\
+      const float B67_b = 0.28466892;\
+      const float B67_c = 0.55991073;\
+      const float B67_inv_r2 = 4.0; /* 1/0.5² */\
+      if (x <= 0.5)\
+          x = x * x * B67_inv_r2;\
+      else\
+          x = exp((x - B67_c) / B67_a) + B67_b;\
+      return x;\
+  }\
+  \
   inline float3 sourceToLinear(float3 rgb) {\
       %s;\
   }\
@@ -1621,6 +1634,15 @@ static HRESULT CompilePixelShader(vout_display_t *vd, const d3d_format_t *format
                     return rgb";
             src_transfer = TRANSFER_FUNC_LINEAR;
             break;
+        case TRANSFER_FUNC_HLG:
+            /* HLG to Linear */
+            psz_src_transform =
+                   "rgb.r = inverse_HLG(rgb.r);\
+                    rgb.g = inverse_HLG(rgb.g);\
+                    rgb.b = inverse_HLG(rgb.b);\
+                    return rgb / 6.0";
+            src_transfer = TRANSFER_FUNC_LINEAR;
+            break;
         default:
             src_transfer = transfer;
             break;