[client] egl: make it possible to configure HDR to SDR mapping

client/renderers/EGL/desktop.c

@@ -51,6 +51,8 @@ struct DesktopShader
   GLint uNVGain;
   GLint uCBMode;
   GLint uIsHDR;
+  GLint uMapHDRtoSDR;
+  GLint uMapHDRGain;
 };
 
 struct EGL_Desktop
@@ -85,6 +87,11 @@ struct EGL_Desktop
   bool useDMA;
   LG_RendererFormat format;
 
+  // map HDR content to SDR
+  bool  mapHDRtoSDR;
+  int   peakLuminance;
+  int   maxCLL;
+
   EGL_PostProcess * pp;
   _Atomic(bool) processFrame;
 };
@@ -110,12 +117,14 @@ static bool egl_initDesktopShader(
     return false;
   }
 
-  shader->uTransform   = egl_shaderGetUniform(shader->shader, "transform"  );
-  shader->uDesktopSize = egl_shaderGetUniform(shader->shader, "desktopSize");
-  shader->uScaleAlgo   = egl_shaderGetUniform(shader->shader, "scaleAlgo"  );
-  shader->uNVGain      = egl_shaderGetUniform(shader->shader, "nvGain"     );
-  shader->uCBMode      = egl_shaderGetUniform(shader->shader, "cbMode"     );
-  shader->uIsHDR       = egl_shaderGetUniform(shader->shader, "isHDR"      );
+  shader->uTransform    = egl_shaderGetUniform(shader->shader, "transform"   );
+  shader->uDesktopSize  = egl_shaderGetUniform(shader->shader, "desktopSize" );
+  shader->uScaleAlgo    = egl_shaderGetUniform(shader->shader, "scaleAlgo"   );
+  shader->uNVGain       = egl_shaderGetUniform(shader->shader, "nvGain"      );
+  shader->uCBMode       = egl_shaderGetUniform(shader->shader, "cbMode"      );
+  shader->uIsHDR        = egl_shaderGetUniform(shader->shader, "isHDR"       );
+  shader->uMapHDRtoSDR  = egl_shaderGetUniform(shader->shader, "mapHDRtoSDR" );
+  shader->uMapHDRGain   = egl_shaderGetUniform(shader->shader, "mapHDRGain"  );
 
   return true;
 }
@@ -184,6 +193,10 @@ bool egl_desktopInit(EGL * egl, EGL_Desktop ** desktop_, EGLDisplay * display,
   desktop->scaleAlgo = option_get_int("egl", "scale"    );
   desktop->useDMA    = useDMA;
 
+  desktop->mapHDRtoSDR   = option_get_bool("egl", "mapHDRtoSDR"  );
+  desktop->peakLuminance = option_get_int ("egl", "peakLuminance");
+  desktop->maxCLL        = option_get_int ("egl", "maxCLL"       );
+
   if (!egl_postProcessInit(&desktop->pp))
   {
     DEBUG_ERROR("Failed to initialize the post process manager");
@@ -274,6 +287,14 @@ void egl_desktopConfigUI(EGL_Desktop * desktop)
   }
   igSliderInt("##nvgain", &desktop->nvGain, 0, desktop->nvMax, format, 0);
   igPopItemWidth();
+
+  igSeparator();
+  igCheckbox("Map HDR content to SDR", &desktop->mapHDRtoSDR);
+  igSliderInt("Peak Luminance", &desktop->peakLuminance, 1, 10000,
+      "%d nits",
+      ImGuiInputTextFlags_CharsDecimal);
+  igSliderInt("Max content light level (nits)", &desktop->maxCLL, 1, 10000,
+      "%d nits", ImGuiInputTextFlags_CharsDecimal);
 }
 
 bool egl_desktopSetup(EGL_Desktop * desktop, const LG_RendererFormat format)
@@ -458,6 +479,9 @@ bool egl_desktopRender(EGL_Desktop * desktop, unsigned int outputWidth,
     desktop->useDMA && texture == desktop->texture ?
       &desktop->dmaShader : &desktop->shader;
 
+  const float mapHDRGain =
+    desktop->maxCLL / desktop->peakLuminance;
+
   EGL_Uniform uniforms[] =
   {
     {
@@ -490,6 +514,16 @@ bool egl_desktopRender(EGL_Desktop * desktop, unsigned int outputWidth,
       .type        = EGL_UNIFORM_TYPE_1I,
       .location    = shader->uIsHDR,
       .i           = { desktop->hdr }
+    },
+    {
+      .type        = EGL_UNIFORM_TYPE_1I,
+      .location    = shader->uMapHDRtoSDR,
+      .i           = { desktop->mapHDRtoSDR }
+    },
+    {
+      .type        = EGL_UNIFORM_TYPE_1F,
+      .location    = shader->uMapHDRGain,
+      .f           = { mapHDRGain }
     }
   };
 

client/renderers/EGL/egl.c

@@ -202,6 +202,27 @@ static struct Option egl_options[] =
     .type         = OPTION_TYPE_BOOL,
     .value.x_bool = true
   },
+  {
+    .module       = "egl",
+    .name         = "mapHDRtoSDR",
+    .description  = "Map HDR content to the SDR color space",
+    .type         = OPTION_TYPE_BOOL,
+    .value.x_bool = true
+  },
+  {
+    .module       = "egl",
+    .name         = "peakLuminance",
+    .description  = "The peak luminance level in nits for HDR to SDR mapping",
+    .type         = OPTION_TYPE_INT,
+    .value.x_int  = 250,
+  },
+  {
+    .module       = "egl",
+    .name         = "maxCLL",
+    .description  = "Maximum content light level in nits for HDR to SDR mapping",
+    .type         = OPTION_TYPE_INT,
+    .value.x_int  = 10000,
+  },
 
   {0}
 };

client/renderers/EGL/shader/desktop_rgb.frag

@@ -21,6 +21,8 @@ uniform int   scaleAlgo;
 uniform float nvGain;
 uniform int   cbMode;
 uniform bool  isHDR;
+uniform bool  mapHDRtoSDR;
+uniform float mapHDRGain;
 
 void main()
 {
@@ -40,8 +42,8 @@ void main()
     }
   }
 
-  if (isHDR)
-    color.rgb = mapToSDR(color.rgb);
+  if (isHDR && mapHDRtoSDR)
+    color.rgb = mapToSDR(color.rgb, mapHDRGain);
 
   if (cbMode > 0)
     color = cbTransform(color, cbMode);

client/renderers/EGL/shader/hdr.h

@@ -13,14 +13,11 @@
  */
 
 // Configuration ---------------------------------------------------------------
-const float peakLuminance = 250.0;   // Peak playback screen luminance in nits
 const float knee          = 0.75;    // Compressor knee position
 const float ratio         = 4.0;     // Compressor ratio: 1 = disabled, <1 = expander
-const float maxCLL        = 10000.0; // Maximum content light level in nits
 // -----------------------------------------------------------------------------
 
 // Precalculated values
-const float gain       = maxCLL / peakLuminance;
 const float compressor = 1.0 / ratio;
 
 // PQ constants
@@ -43,10 +40,11 @@ float midGain(vec3 pixel)
       min(pixel.r, pixel.g)); // min = b
 }
 
-vec3 compress(vec3 pixel)
+vec3 compress(vec3 pixel, float gain)
 {
-  float gain = maxGain(pixel);
-  return pixel * (gain < knee ? gain : knee + max(gain - knee, 0.0) * compressor) / gain;
+  float maxGain = maxGain(pixel);
+  return pixel * (maxGain < knee ? maxGain :
+      knee + max(maxGain - knee, 0.0) * compressor) / maxGain;
 }
 
 vec3 fixClip(vec3 pixel)
@@ -67,7 +65,7 @@ vec3 fixClip(vec3 pixel)
 }
 
 // Returns luminance in nits
-vec3 pq2lin(vec3 pq)
+vec3 pq2lin(vec3 pq, float gain)
 {
   vec3 p = pow(pq, vec3(m2inv));
   vec3 d = max(p - c1, vec3(0.0)) / (c2 - c3 * p);
@@ -101,8 +99,8 @@ vec3 bt2020to709(vec3 bt2020)
     bt2020.r * -0.0182 + bt2020.g * -0.1006 + bt2020.b * 1.1187);
 }
 
-vec3 mapToSDR(vec3 color)
+vec3 mapToSDR(vec3 color, float gain)
 {
-  vec3 lin = bt2020to709(pq2lin(color.rgb));
-  return lin2srgb(compress(lin));
+  vec3 lin = bt2020to709(pq2lin(color.rgb, gain));
+  return lin2srgb(compress(lin, gain));
 }