[FFmpeg-devel] [PATCH] hevc: Add support for alternative transfer characterics SEI

[James Almer]

On 6/9/2017 6:35 PM, Vittorio Giovara wrote:
> Signed-off-by: Vittorio Giovara <vittorio.giovara at gmail.com>
> ---
>  libavcodec/hevc_sei.c | 9 +++++++++
>  libavcodec/hevc_sei.h | 7 +++++++
>  libavcodec/hevcdec.c  | 5 +++++
>  3 files changed, 21 insertions(+)
> 
> diff --git a/libavcodec/hevc_sei.c b/libavcodec/hevc_sei.c
> index f0ad84f2f4..cd55d50212 100644
> --- a/libavcodec/hevc_sei.c
> +++ b/libavcodec/hevc_sei.c
> @@ -265,6 +265,13 @@ static int decode_nal_sei_active_parameter_sets(HEVCSEIContext *s, GetBitContext
>      return 0;
>  }
>  
> +static int decode_nal_sei_alternative_transfer(HEVCSEIAlternativeTransfer *s, GetBitContext *gb)
> +{
> +    s->present = 1;
> +    s->preferred_transfer_characteristics = get_bits(gb, 8);
> +    return 0;
> +}
> +
>  static int decode_nal_sei_prefix(GetBitContext *gb, HEVCSEIContext *s, const HEVCParamSets *ps,
>                                   int type, int size, void *logctx)
>  {
> @@ -285,6 +292,8 @@ static int decode_nal_sei_prefix(GetBitContext *gb, HEVCSEIContext *s, const HEV
>          return decode_nal_sei_active_parameter_sets(s, gb, logctx);
>      case HEVC_SEI_TYPE_USER_DATA_REGISTERED_ITU_T_T35:
>          return decode_nal_sei_user_data_registered_itu_t_t35(s, gb, size);
> +    case HEVC_SEI_TYPE_ALTERNATIVE_TRANSFER_CHARACTERISTICS:
> +        return decode_nal_sei_alternative_transfer(&s->alternative_transfer, gb);
>      default:
>          av_log(logctx, AV_LOG_DEBUG, "Skipped PREFIX SEI %d\n", type);
>          skip_bits_long(gb, 8 * size);
> diff --git a/libavcodec/hevc_sei.h b/libavcodec/hevc_sei.h
> index 5645e4f5de..1b522227ec 100644
> --- a/libavcodec/hevc_sei.h
> +++ b/libavcodec/hevc_sei.h
> @@ -56,6 +56,7 @@ 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 {
> @@ -100,6 +101,11 @@ typedef struct HEVCSEIContentLight {
>      uint16_t max_pic_average_light_level;
>  } HEVCSEIContentLight;
>  
> +typedef struct HEVCSEIAlternativeTransfer {
> +    int present;
> +    int preferred_transfer_characteristics;
> +} HEVCSEIAlternativeTransfer;
> +
>  typedef struct HEVCSEIContext {
>      HEVCSEIPictureHash picture_hash;
>      HEVCSEIFramePacking frame_packing;
> @@ -109,6 +115,7 @@ typedef struct HEVCSEIContext {
>      HEVCSEIMasteringDisplay mastering_display;
>      HEVCSEIContentLight content_light;
>      int active_seq_parameter_set_id;
> +    HEVCSEIAlternativeTransfer alternative_transfer;
>  } HEVCSEIContext;
>  
>  struct HEVCParamSets;
> diff --git a/libavcodec/hevcdec.c b/libavcodec/hevcdec.c
> index 23a89345a8..955cc703cf 100644
> --- a/libavcodec/hevcdec.c
> +++ b/libavcodec/hevcdec.c
> @@ -2684,6 +2684,11 @@ static int set_side_data(HEVCContext *s)
>          s->avctx->properties |= FF_CODEC_PROPERTY_CLOSED_CAPTIONS;
>      }
>  
> +    if (s->sei.alternative_transfer.present &&
> +        s->sei.alternative_transfer.preferred_transfer_characteristics != AVCOL_SPC_UNSPECIFIED) {

Shouldn't this be AVCOL_TRC_UNSPECIFIED?
And validate it with av_color_transfer_name() instead, like it's done in
hevc_ps.c with the VUI value.

> +        s->avctx->color_trc = s->sei.alternative_transfer.preferred_transfer_characteristics;

Did you make sure avctx->color_trc will not be overwritten by the VUI
value after this? As in, what's called first, set_side_data() or
export_stream_params()? And is it properly propagated in updates between
thread contexts?

> +    }
> +
>      return 0;
>  }
>  
>