hevc: Add support for alternative transfer characterics SEI

The use of this SEI is for backward compatibility in HLG HDR systems:
older devices that cannot interpret the "arib-std-b67" transfer will
get the compatible transfer (usually bt709 or bt2020) from the VUI,
while newer devices that can interpret HDR will read the SEI and use
its value instead.

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/libavcodec/hevc_sei.h b/libavcodec/hevc_sei.h
index b699fef45d..e4aeac1fbe 100644
--- a/libavcodec/hevc_sei.h
+++ b/libavcodec/hevc_sei.h
@@ -54,6 +54,7 @@ typedef enum {
     HEVC_SEI_TYPE_REGION_REFRESH_INFO                  = 134,
     HEVC_SEI_TYPE_MASTERING_DISPLAY_INFO               = 137,
     HEVC_SEI_TYPE_CONTENT_LIGHT_LEVEL_INFO             = 144,
+    HEVC_SEI_TYPE_ALTERNATIVE_TRANSFER_CHARACTERISTICS = 147,
 } HEVC_SEI_Type;
 
 typedef struct HEVCSEIPictureHash {
@@ -74,10 +75,16 @@ typedef struct HEVCSEIDisplayOrientation {
     int hflip, vflip;
 } HEVCSEIDisplayOrientation;
 
+typedef struct HEVCSEIAlternativeTransfer {
+    int present;
+    int preferred_transfer_characteristics;
+} HEVCSEIAlternativeTransfer;
+
 typedef struct HEVCSEI {
     HEVCSEIPictureHash picture_hash;
     HEVCSEIFramePacking frame_packing;
     HEVCSEIDisplayOrientation display_orientation;
+    HEVCSEIAlternativeTransfer alternative_transfer;
 } HEVCSEI;
 
 int ff_hevc_decode_nal_sei(GetBitContext *gb, void *logctx, HEVCSEI *s,