video: Include better heuristics for guessing primaries

These consult the vertical resolution, matching against 576 for
PAL and 480/486 for NTSC. The documentation has also been updated.

Signed-off-by: wm4 <wm4@nowhere>

1 files changed, 19 insertions, 0 deletions

diff --git a/video/csputils.c b/video/csputils.c
index 202585187a..c462c43c34 100644
--- a/video/csputils.c
+++ b/video/csputils.c
@@ -160,6 +160,25 @@ enum mp_csp mp_csp_guess_colorspace(int width, int height)
     return width >= 1280 || height > 576 ? MP_CSP_BT_709 : MP_CSP_BT_601;
 }
 
+enum mp_csp_prim mp_csp_guess_primaries(int width, int height)
+{
+    // HD content
+    if (width >= 1280 || height > 576)
+        return MP_CSP_PRIM_BT_709;
+
+    switch (height) {
+    case 576: // Typical PAL content, including anamorphic/squared
+        return MP_CSP_PRIM_BT_601_625;
+
+    case 480: // Typical NTSC content, including squared
+    case 486: // NTSC Pro or anamorphic NTSC
+        return MP_CSP_PRIM_BT_601_525;
+
+    default: // No good metric, just pick BT.709 to minimize damage
+        return MP_CSP_PRIM_BT_709;
+    }
+}
+
 enum mp_chroma_location avchroma_location_to_mp(int avloc)
 {
     switch (avloc) {