[FFmpeg-devel] [PATCH] lavc/x265: set preferred_transfer_characteristics for HLG

James Almer jamrial at gmail.com
Thu Dec 12 18:14:08 EET 2019


On 12/4/2019 11:24 AM, Zhong Li wrote:
> "HEVC HDR UHDTV Bitstreams using HLG10 shall also contain the
> alternative_transfer_characteristics SEI message. The
> alternative_transfer_characteristics SEI message shall be inserted on
> the HEVC DVB_RAP, and preferred_transfer_characteristics shall be set
> equal to "18", indicating Recommendation ITU-R BT. 2100 [45] HLG
> system."
> 
> Signed-off-by: Zhong Li <zhongli_dev at 126.com>
> ---
>  libavcodec/libx265.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/libavcodec/libx265.c b/libavcodec/libx265.c
> index 4e75077..963c28f 100644
> --- a/libavcodec/libx265.c
> +++ b/libavcodec/libx265.c
> @@ -159,6 +159,10 @@ static av_cold int libx265_encode_init(AVCodecContext *avctx)
>          // x265 validates the parameters internally
>          ctx->params->vui.colorPrimaries          = avctx->color_primaries;
>          ctx->params->vui.transferCharacteristics = avctx->color_trc;
> +#if X265_BUILD >= 159
> +        if (avctx->color_trc == AVCOL_TRC_ARIB_STD_B67)
> +            ctx->params->preferredTransferCharacteristics = ctx->params->vui.transferCharacteristics;
> +#endif

isn't the point of preferred_transfer_characteristics to have the Arib
value at the same time the standard VUI trc field contains a value like
BT2020 instead, for device backwards compat purposes?

If both have the Arib value, then it seems redundant.

>          ctx->params->vui.matrixCoeffs            = avctx->colorspace;
>      }
>  
> 



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