support conversions with BT.601 chromicities

Added experimental support for conversions with BT.601 primaries. The command-line interface will most likely change.
MartinPulec · Sep 27, 2024 · cf6acad · cf6acad
1 parent 4c17aa9
commit cf6acad
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Showing 3 changed files with 37 additions and 13 deletions.
diff --git a/src/color.c b/src/color.c
@@ -40,6 +40,7 @@
 #include <stdio.h>   // for fprintf, stderr
 #include <stdlib.h>  // for abort
 
+#include "host.h"    // for ADD_TO_PARAM
 #include "types.h"   // for depth
 
 #define D(kr, kb) (2. * ((kr) + KG(kr, kb)))
@@ -91,8 +92,11 @@
                 SCALED(B_CB(depth, kr, kb)), \
         }
 
+#define COEFFS_601(depth) COEFFS(depth, KR_601, KB_601)
 #define COEFFS_709(depth) COEFFS(depth, KR_709, KB_709)
 
+ADD_TO_PARAM("color-601", "* color-601\n"
+                "  Use BT.601 color primaries.\n");
 /**
  * @brief returns color coefficient for RGB<-YCbCr conversion
  *
@@ -109,21 +113,31 @@
 const struct color_coeffs *
 get_color_coeffs(int ycbcr_bit_depth)
 {
-        static const struct color_coeffs col_cfs_8  = COEFFS_709(DEPTH8);
-        static const struct color_coeffs col_cfs_10 = COEFFS_709(DEPTH10);
-        static const struct color_coeffs col_cfs_12 = COEFFS_709(DEPTH12);
-        static const struct color_coeffs col_cfs_16 = COEFFS_709(DEPTH16);
+        static _Atomic int primaries_index = -1;
+        if (primaries_index == -1) {
+                primaries_index =
+                    get_commandline_param("color-601") != NULL ? 0 : 1;
+        }
+
+        static const struct {
+                struct color_coeffs col_cfs[2];
+        } coeffs[] = {
+                { { COEFFS_601(DEPTH8),  COEFFS_709(DEPTH8)  } },
+                { { COEFFS_601(DEPTH10), COEFFS_709(DEPTH10) } },
+                { { COEFFS_601(DEPTH12), COEFFS_709(DEPTH12) } },
+                { { COEFFS_601(DEPTH16), COEFFS_709(DEPTH16) } }
+        };
         switch ((enum depth) ycbcr_bit_depth) {
         case DEPTH8:
-                return &col_cfs_8;
+                return &coeffs[0].col_cfs[primaries_index];
         case DEPTH10:
-                return &col_cfs_10;
+                return &coeffs[1].col_cfs[primaries_index];
         case DEPTH12:
-                return &col_cfs_12;
+                return &coeffs[2].col_cfs[primaries_index];
         case DEPTH16:
-                return &col_cfs_16;
+                return &coeffs[3].col_cfs[primaries_index];
         }
-        fprintf(stderr, "%s: Wrong depth %d!\n", __func__,
-                ycbcr_bit_depth);
+
+        fprintf(stderr, "%s: Wrong depth %d!\n", __func__, ycbcr_bit_depth);
         abort();
 }
diff --git a/src/color.h b/src/color.h
@@ -83,6 +83,8 @@ static_assert(sizeof(comp_type_t) * 8 >= COMP_BASE + 18, "comp_type_t not wide e
         (224. * (1 << ((out_depth) - 8)) / ((1 << (out_depth)) - 1))
 #endif // !defined YCBCR_FULL
 
+#define KR_601 .299
+#define KB_601 .114
 #define KR_709 .212639
 #define KB_709 .072192
 #define KR_2020 .262700
@@ -152,14 +154,18 @@ static_assert(sizeof(comp_type_t) * 8 >= COMP_BASE + 18, "comp_type_t not wide e
 extern "C" {
 #endif
 
-// new API
 struct color_coeffs {
+        // shorts are used the compiler can use 2-byte words in the vecotred
+        // instruction, which is faster (and the values fit)
         short y_r,  y_g,  y_b;
         short cb_r, cb_g, cb_b;
         short cr_r, cr_g, cr_b;
 
+        // the shorts below doesn't seem to be necessary - it seems like the
+        // compiler doesn't vectorise those conversions (in contrary to the
+        // above coeffs)
         short r_cr, g_cb, g_cr;
-        int b_cb; // b_cb is 34712 so doesn't fit to 16-bit short
+        int   b_cb; // is 34712 for 709  so doesn't fit to 16-bit short
 };
 const struct color_coeffs *get_color_coeffs(int ycbcr_bit_depth);
 #ifdef __cplusplus

diff --git a/src/video_display/gl.cpp b/src/video_display/gl.cpp
@@ -1525,7 +1525,11 @@ static GLuint gl_substitute_compile_link(const char *vprogram, const char *fprog
                         LOG(LOG_LEVEL_WARNING) << MOD_NAME "Wrong chromicities index " << color << "\n";
                 }
         }
-        double cs_coeffs[2*4] = { 0, 0, KR_709, KB_709, KR_2020, KB_2020, KR_P3, KB_P3 };
+        if (get_commandline_param("color-601") != nullptr) {
+                index = 0;
+        }
+        double cs_coeffs[2 * 4] = { KR_601,  KB_601,  KR_709, KB_709,
+                                    KR_2020, KB_2020, KR_P3,  KB_P3 };
         double kr = cs_coeffs[2 * index];
         double kb = cs_coeffs[2 * index + 1];
         const char *placeholders[] = { "Y_SCALED_PLACEHOLDER", "R_CR_PLACEHOLDER", "G_CB_PLACEHOLDER", "G_CR_PLACEHOLDER", "B_CB_PLACEHOLDER" };