[PATCH 6/8] edid-decode: support HLG, decode luminance values

[Hans Verkuil]

From: Hans Verkuil <hans.verkuil at cisco.com>

Add support for the new CTA-861-G Hybrid Log-Gamma transfer
function.

Also decode the luminance values in the static metadata block to
cd/m^2 values.

Signed-off-by: Hans Verkuil <hans.verkuil at cisco.com>
---
 Makefile      |  2 +-
 edid-decode.c | 15 ++++++++++-----
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/Makefile b/Makefile
index 21b811ed..b698c579 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@ bindir ?= /usr/bin
 mandir ?= /usr/share/man
 
 edid-decode: edid-decode.c
-	$(CC) $(CFLAGS) -g -Wall -o $@ $<
+	$(CC) $(CFLAGS) -g -Wall -lm -o $@ $<
 
 clean:
 	rm -f edid-decode
diff --git a/edid-decode.c b/edid-decode.c
index d0da48e2..effcf777 100644
--- a/edid-decode.c
+++ b/edid-decode.c
@@ -31,6 +31,7 @@
 #include <stdlib.h>
 #include <time.h>
 #include <ctype.h>
+#include <math.h>
 
 #define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))
 #define min(a, b) ((a) < (b) ? (a) : (b))
@@ -1827,10 +1828,11 @@ static const char *eotf_map[] = {
     "Traditional gamma - SDR luminance range",
     "Traditional gamma - HDR luminance range",
     "SMPTE ST2084",
+    "Hybrid Log-Gamma",
 };
 
 static void
-cea_hdr_metadata_block(unsigned char *x)
+cea_hdr_static_metadata_block(unsigned char *x)
 {
     int length = x[0] & 0x1f;
     int i;
@@ -1851,13 +1853,16 @@ cea_hdr_metadata_block(unsigned char *x)
     }
 
     if (length >= 4)
-	printf("    Desired content max luminance: %d\n", x[4]);
+	printf("    Desired content max luminance: %d (%.3f cd/m^2)\n",
+	       x[4], 50.0 * pow(2, x[4] / 32.0));
 
     if (length >= 5)
-	printf("    Desired content max frame-average luminance: %d\n", x[5]);
+	printf("    Desired content max frame-average luminance: %d (%.3f cd/m^2)\n",
+	       x[5], 50.0 * pow(2, x[5] / 32.0));
 
     if (length >= 6)
-	printf("    Desired content min luminance: %d\n", x[6]);
+	printf("    Desired content min luminance: %d (%.3f cd/m^2)\n",
+	       x[6], (50.0 * pow(2, x[4] / 32.0)) * pow(x[6] / 255.0, 2) / 100.0);
 }
 
 static void
@@ -1924,7 +1929,7 @@ cea_block(unsigned char *x)
 		    break;
 		case 0x06:
 		    printf("HDR static metadata data block\n");
-		    cea_hdr_metadata_block(x);
+		    cea_hdr_static_metadata_block(x);
 		    break;
 		case 0x0d:
 		    printf("Video format preference data block\n");
-- 
2.14.1