add BT.2020 support

README.txt

@@ -41,7 +41,9 @@ string srt_font:
     Defaults to whatever Fontconfig chooses for “sans-serif”.
 string colorspace:
     The color space of your (YUV) video. Possible values:
+        - Rec2020, BT.2020
         - Rec709, BT.709
         - Rec601, BT.601
     Default is to use the ASS script’s “Video Colorspace” property, else guess
-    based on video resolution (width > 1280 or height > 576 → BT.709).
+    based on video resolution (width > 1920 or height > 1080 → BT.2020,
+    then width > 1280 or height > 576 → BT.709).

src/assrender.c

@@ -177,8 +177,12 @@ AVS_Value AVSC_CC assrender_create(AVS_ScriptEnvironment* env, AVS_Value args,
         data->colorspace = BT709;
     else if (!strcasecmp(tmpcsp, "bt.601") || !strcasecmp(tmpcsp, "rec601"))
         data->colorspace = BT601;
+    else if (!strcasecmp(tmpcsp, "bt.2020") || !strcasecmp(tmpcsp, "rec2020"))
+        data->colorspace = BT2020;
     else {
-        if (fi->vi.width > 1280 || fi->vi.height > 576)
+        if (fi->vi.width > 1920 || fi->vi.height > 1080)
+            data->colorspace = BT2020;
+        else if (fi->vi.width > 1280 || fi->vi.height > 576)
             data->colorspace = BT709;
         else
             data->colorspace = BT601;

src/assrender.h

@@ -18,7 +18,8 @@
 
 enum csp {
     BT601,
-    BT709
+    BT709,
+    BT2020
 };
 
 enum plane { Y, U, V };

src/render.c

@@ -89,10 +89,14 @@ void blit444(ASS_Image* img, uint8_t* dataY, uint8_t* dataU, uint8_t* dataV,
             y = rgb2y709(img->color);
             u = rgb2u709(img->color);
             v = rgb2v709(img->color);
-        } else {
+        } else if (colorspace == BT601) {
             y = rgb2y601(img->color);
             u = rgb2u601(img->color);
             v = rgb2v601(img->color);
+        } else {
+            y = rgb2y2020(img->color);
+            u = rgb2u2020(img->color);
+            v = rgb2v2020(img->color);
         }
 
         opacity = 255 - _a(img->color);
@@ -262,8 +266,10 @@ AVS_VideoFrame* AVSC_CC assrender_get_frame(AVS_FilterInfo* p, int n)
 
                     if (ud->colorspace == BT709) {
                         y = rgb2y709(img->color);
-                    } else {
+                    } else if (ud->colorspace == BT601) {
                         y = rgb2y601(img->color);
+                    } else {
+                        y = rgb2y2020(img->color);
                     }
 
                     uint8_t opacity = 255 - _a(img->color);

src/render.h

@@ -21,6 +21,10 @@
 #define rgb2u709(c)  ((div65536(-6596 * _r(c) - 22189 * _g(c) + 28784 * _b(c)) + 128))
 #define rgb2v709(c)  ((div65536(28784 * _r(c) - 26145 * _g(c) - 2639  * _b(c)) + 128))
 
+#define rgb2y2020(c) ((div65536(14786 * _r(c) + 38160 * _g(c) + 3338  * _b(c)) + 16))
+#define rgb2u2020(c) ((div65536(-8038 * _r(c) - 20746 * _g(c) + 28784 * _b(c)) + 128))
+#define rgb2v2020(c) ((div65536(28784 * _r(c) - 26469 * _g(c) - 2315  * _b(c)) + 128))
+
 #define blend(srcA, srcC, dstC) \
     ((div255(srcA * srcC + (255 - srcA) * dstC)))
 #define scale(srcA, srcC, dstC) \