csputils: add Panasonic V-Gamut primaries

This is actually not entirely trivial since it involves negative Yxy
coordinates, so the CMM has to be capable of full floating point
operation. Fortunately, LittleCMS is, so we can just blindly implement
it.

DOCS/man/vf.rst

@@ -288,6 +288,7 @@ Available filters are:
         :adobe:        Adobe RGB (1998)
         :prophoto:     ProPhoto RGB (ROMM)
         :cie1931:      CIE 1931 RGB
+        :v-gamut:      Panasonic V-Gamut primaries
 
     ``<gamma>``
        Gamma function the source file was encoded with. Normally this should be set

DOCS/man/vo.rst

@@ -979,6 +979,8 @@ Available video output drivers are:
             CIE 1931 RGB (not to be confused with CIE XYZ)
         dci-p3
             DCI-P3 (Digital Cinema Colorspace), SMPTE RP431-2
+        v-gamut
+            Panasonic V-Gamut (VARICAM) primaries
 
     ``target-trc=<value>``
         Specifies the transfer characteristics (gamma) of the display. Video

video/csputils.c

@@ -65,6 +65,7 @@ const struct m_opt_choice_alternatives mp_csp_prim_names[] = {
     {"prophoto",    MP_CSP_PRIM_PRO_PHOTO},
     {"cie1931",     MP_CSP_PRIM_CIE_1931},
     {"dci-p3",      MP_CSP_PRIM_DCI_P3},
+    {"v-gamut",     MP_CSP_PRIM_V_GAMUT},
     {0}
 };
 
@@ -422,6 +423,14 @@ struct mp_csp_primaries mp_get_csp_primaries(enum mp_csp_prim spc)
             .blue  = {0.150, 0.060},
             .white = d65
         };
+    // From Panasonic VARICAM reference manual
+    case MP_CSP_PRIM_V_GAMUT:
+        return (struct mp_csp_primaries) {
+            .red   = {0.730, 0.280},
+            .green = {0.165, 0.840},
+            .blue  = {0.100, -0.03},
+            .white = d65
+        };
     default:
         return (struct mp_csp_primaries) {{0}};
     }

video/csputils.h

@@ -64,6 +64,7 @@ enum mp_csp_prim {
     MP_CSP_PRIM_PRO_PHOTO,
     MP_CSP_PRIM_CIE_1931,
     MP_CSP_PRIM_DCI_P3,
+    MP_CSP_PRIM_V_GAMUT,
     MP_CSP_PRIM_COUNT
 };