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, 6 insertions, 0 deletions

diff --git a/libavcodec/hevcdec.c b/libavcodec/hevcdec.c
index 7a9182af9b..ac0b1a3c1d 100644
--- a/libavcodec/hevcdec.c
+++ b/libavcodec/hevcdec.c
@@ -2407,6 +2407,12 @@ static int set_side_data(HEVCContext *s)
                                s->sei.display_orientation.vflip);
     }
 
+    if (s->sei.alternative_transfer.present &&
+        av_color_transfer_name(s->sei.alternative_transfer.preferred_transfer_characteristics) &&
+        s->sei.alternative_transfer.preferred_transfer_characteristics != AVCOL_TRC_UNSPECIFIED) {
+        s->avctx->color_trc = s->sei.alternative_transfer.preferred_transfer_characteristics;
+    }
+
     return 0;
 }