Update mpv config:

mpv/shaders/hdr-toys/transfer-function/bt709.glsl

@@ -0,0 +1,30 @@
+// https://www.itu.int/rec/R-REC-BT.601
+// https://www.itu.int/rec/R-REC-BT.709
+// https://www.itu.int/rec/R-REC-BT.2020
+
+//!HOOK OUTPUT
+//!BIND HOOKED
+//!DESC transfer function (bt.709)
+
+const float beta = 0.018053968510807;
+const float alpha = 1.0 + 5.5 * beta;
+
+float bt709_oetf(float L) {
+    return L < beta ? 4.5 * L : alpha * pow(L, 0.45) - (alpha - 1.0);
+}
+
+vec3 bt709_oetf(vec3 color) {
+    return vec3(
+        bt709_oetf(color.r),
+        bt709_oetf(color.g),
+        bt709_oetf(color.b)
+    );
+}
+
+vec4 hook() {
+    vec4 color = HOOKED_tex(HOOKED_pos);
+
+    color.rgb = bt709_oetf(color.rgb);
+
+    return color;
+}