Re: [FFmpeg-devel] [PATCH 1/4] avcodec/cbs_{h2645, sei}: add support for Ambient Viewing Environment SEI

[James Almer <jamrial@gmail.com>]

On 1/10/2023 6:19 PM, Jan Ekström wrote:
> Defined by H.274, this SEI message is utilized by iPhones to save
> the nominal ambient viewing environment for the display of recorded
> HDR content.
> ---
>   libavcodec/cbs_h2645.c               |  6 ++++++
>   libavcodec/cbs_sei.h                 |  6 ++++++
>   libavcodec/cbs_sei_syntax_template.c | 17 +++++++++++++++++
>   3 files changed, 29 insertions(+)
> 
> diff --git a/libavcodec/cbs_h2645.c b/libavcodec/cbs_h2645.c
> index 4ee06003c3..80e48829af 100644
> --- a/libavcodec/cbs_h2645.c
> +++ b/libavcodec/cbs_h2645.c
> @@ -1500,6 +1500,12 @@ static const SEIMessageTypeDescriptor cbs_sei_common_types[] = {
>           sizeof(SEIRawAlternativeTransferCharacteristics),
>           SEI_MESSAGE_RW(sei, alternative_transfer_characteristics),
>       },
> +    {
> +        SEI_TYPE_AMBIENT_VIEWING_ENVIRONMENT,
> +        1, 0,
> +        sizeof(SEIRawAmbientViewingEnvironment),
> +        SEI_MESSAGE_RW(sei, ambient_viewing_environment),
> +    },
>       SEI_MESSAGE_TYPE_END,
>   };
>   
> diff --git a/libavcodec/cbs_sei.h b/libavcodec/cbs_sei.h
> index c7a7a95be0..1c327a4689 100644
> --- a/libavcodec/cbs_sei.h
> +++ b/libavcodec/cbs_sei.h
> @@ -65,6 +65,12 @@ typedef struct SEIRawAlternativeTransferCharacteristics {
>       uint8_t preferred_transfer_characteristics;
>   } SEIRawAlternativeTransferCharacteristics;
>   
> +typedef struct SEIRawAmbientViewingEnvironment {
> +    uint32_t ambient_illuminance;
> +    uint16_t ambient_light_x;
> +    uint16_t ambient_light_y;
> +} SEIRawAmbientViewingEnvironment;
> +
>   typedef struct SEIRawMessage {
>       uint32_t     payload_type;
>       uint32_t     payload_size;
> diff --git a/libavcodec/cbs_sei_syntax_template.c b/libavcodec/cbs_sei_syntax_template.c
> index 0ef7b42ed9..6a7cc36dda 100644
> --- a/libavcodec/cbs_sei_syntax_template.c
> +++ b/libavcodec/cbs_sei_syntax_template.c
> @@ -144,6 +144,23 @@ static int FUNC(alternative_transfer_characteristics)
>       return 0;
>   }
>   
> +static int FUNC(ambient_viewing_environment)
> +    (CodedBitstreamContext *ctx, RWContext *rw,
> +     SEIRawAmbientViewingEnvironment *current,
> +     SEIMessageState *state)
> +{
> +    static const uint16_t max_ambient_light_value = 50000;
> +    int err;
> +
> +    HEADER("Ambient Viewing Environment");
> +
> +    u(32, ambient_illuminance, 1, MAX_UINT_BITS(32));
> +    u(16, ambient_light_x, 0, max_ambient_light_value);
> +    u(16, ambient_light_y, 0, max_ambient_light_value);
> +
> +    return 0;
> +}
> +
>   static int FUNC(message)(CodedBitstreamContext *ctx, RWContext *rw,
>                            SEIRawMessage *current)
>   {

Should be ok.
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