On 6/13/17 8:54 PM, Vittorio Giovara wrote:
> 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
> ---
> Expanded commit log and better validated the SEI contents.
> Vittorio
>
> libavcodec/hevc_sei.c | 9 +
> libavcodec/hevc_sei.h | 7 +++
> libavcodec/hevcdec.c | 6 ++
> 3 files changed, 22 insertions(+)
>
> diff --git a/libavcodec/hevc_sei.c b/libavcodec/hevc_sei.c
> index 153d211b4b..0a5d4440bf 100644
> --- a/libavcodec/hevc_sei.c
> +++ b/libavcodec/hevc_sei.c
> @@ -86,6 +86,13 @@ static int
> decode_nal_sei_display_orientation(HEVCSEIDisplayOrientation *s, GetB
> 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, void *logctx, HEVCSEI *s,
> int type, int size)
> {
> @@ -96,6 +103,8 @@ static int decode_nal_sei_prefix(GetBitContext *gb, void
> *logctx, HEVCSEI *s,
> return decode_nal_sei_frame_packing_arrangement(&s->frame_packing,
> gb);
> case HEVC_SEI_TYPE_DISPLAY_ORIENTATION:
> return decode_nal_sei_display_orientation(&s->display_orientation,
> gb);
> +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 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,
> 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;
> }
>
>
Still ok.
lu
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