Re: [FFmpeg-devel] [PATCH v3 1/5] avutil: add ambient viewing environment metadata side data

[Lynne <dev@lynne.ee>]

5 Apr 2022, 17:32 by andreas.rheinhardt@outlook.com:

> lance.lmwang@gmail.com:
>
>> From: Limin Wang <lance.lmwang@gmail.com>
>>
>> Signed-off-by: Limin Wang <lance.lmwang@gmail.com>
>> ---
>>  libavutil/frame.c                      |  1 +
>>  libavutil/frame.h                      |  6 +++++
>>  libavutil/mastering_display_metadata.c | 23 +++++++++++++++++
>>  libavutil/mastering_display_metadata.h | 45 ++++++++++++++++++++++++++++++++++
>>  libavutil/version.h                    |  2 +-
>>  5 files changed, 76 insertions(+), 1 deletion(-)
>>
>> diff --git a/libavutil/frame.c b/libavutil/frame.c
>> index fbb869f..8882da2 100644
>> --- a/libavutil/frame.c
>> +++ b/libavutil/frame.c
>> @@ -815,6 +815,7 @@ const char *av_frame_side_data_name(enum AVFrameSideDataType type)
>>  case AV_FRAME_DATA_DETECTION_BBOXES:            return "Bounding boxes for object detection and classification";
>>  case AV_FRAME_DATA_DOVI_RPU_BUFFER:             return "Dolby Vision RPU Data";
>>  case AV_FRAME_DATA_DOVI_METADATA:               return "Dolby Vision Metadata";
>> +    case AV_FRAME_DATA_AMBIENT_VIEWING_ENV:         return "Ambient Viewing Environment";
>>  }
>>  return NULL;
>>  }
>> diff --git a/libavutil/frame.h b/libavutil/frame.h
>> index 33fac20..92413c9 100644
>> --- a/libavutil/frame.h
>> +++ b/libavutil/frame.h
>> @@ -209,6 +209,12 @@ enum AVFrameSideDataType {
>>  * volume transform - CUVA 005.1-2021.
>>  */
>>  AV_FRAME_DATA_DYNAMIC_HDR_VIVID,
>> +
>> +    /**
>> +     * ambient viewing environment for a video frame, as described by
>> +     * the AVAmbientViewingEnv
>> +     */
>> +    AV_FRAME_DATA_AMBIENT_VIEWING_ENV,
>>  };
>>  
>>  enum AVActiveFormatDescription {
>> diff --git a/libavutil/mastering_display_metadata.c b/libavutil/mastering_display_metadata.c
>> index 6069347..f094eab 100644
>> --- a/libavutil/mastering_display_metadata.c
>> +++ b/libavutil/mastering_display_metadata.c
>> @@ -64,3 +64,26 @@ AVContentLightMetadata *av_content_light_metadata_create_side_data(AVFrame *fram
>>  
>>  return (AVContentLightMetadata *)side_data->data;
>>  }
>> +
>> +AVAmbientViewingEnv *av_ambient_viewing_env_alloc(size_t *size)
>> +{
>> +    AVAmbientViewingEnv *metadata = av_mallocz(sizeof(*metadata));
>> +
>> +    if (size)
>> +        *size = sizeof(*metadata);
>> +
>> +    return metadata;
>> +}
>> +
>> +AVAmbientViewingEnv *av_ambient_viewing_env_create_side_data(AVFrame *frame)
>> +{
>> +    AVFrameSideData *side_data = av_frame_new_side_data(frame,
>> +            AV_FRAME_DATA_AMBIENT_VIEWING_ENV,
>> +            sizeof(AVAmbientViewingEnv));
>> +    if (!side_data)
>> +        return NULL;
>> +
>> +    memset(side_data->data, 0, sizeof(AVAmbientViewingEnv));
>> +
>> +    return (AVAmbientViewingEnv *)side_data->data;
>> +}
>> diff --git a/libavutil/mastering_display_metadata.h b/libavutil/mastering_display_metadata.h
>> index c23b07c..c1ba659 100644
>> --- a/libavutil/mastering_display_metadata.h
>> +++ b/libavutil/mastering_display_metadata.h
>> @@ -125,4 +125,49 @@ AVContentLightMetadata *av_content_light_metadata_alloc(size_t *size);
>>  */
>>  AVContentLightMetadata *av_content_light_metadata_create_side_data(AVFrame *frame);
>>  
>> +/**
>> + * The characteristics of the nominal ambient viewing environment for
>> + * the display of the associated video content.
>> + * To be used as payload of a AVFrameSideData the appropriate type.
>> + *
>> + * @note The struct should be allocated with av_ambient_viewing_env_alloc()
>> + *       and its size is not a part of the public ABI.
>> + */
>> +typedef struct AVAmbientViewingEnv {
>> +    /**
>> +     * specifies the environmental illuminance of the ambient viewing
>> +     * environment in units of 0.0001 lux.
>> +     * ambient_illuminance shall not be equal to 0.
>> +     */
>> +    uint32_t ambient_illuminance;
>> +    /**
>> +     * specify the normalized x and y chromaticity coordinates, respectively,
>> +     * of the environmental ambient light in the nominal viewing environment,
>> +     * according to the CIE 1931 definition of x and y as specified in ISO
>> +     * 11664-1 (see also ISO 11664-3 and CIE 15), in normalized increments of
>> +     * 0.00002. The values of ambient_light_x and ambient_light_y shall be in
>> +     * the range of 0 to 50000
>> +     */
>> +    uint16_t ambient_light_x;
>> +    uint16_t ambient_light_y;
>> +} AVAmbientViewingEnv;
>> +
>> +/**
>> + * Allocate an AVAmbientViewingEnv structure and set its fields to
>> + * default values. The resulting struct can be freed using av_freep().
>> + *
>> + * @return An AVAmbientViewingEnv filled with default values or NULL
>> + *         on failure.
>> + */
>> +AVAmbientViewingEnv *av_ambient_viewing_env_alloc(size_t *size);
>> +
>> +/**
>> + * Allocate a complete AVAmbientViewingEnv and add it to the frame.
>> + *
>> + * @param frame The frame which side data is added to.
>> + *
>> + * @return The AVAmbientViewingEnv structure to be filled by caller.
>> + */
>> +AVAmbientViewingEnv *av_ambient_viewing_env_create_side_data(AVFrame *frame);
>>
>
> All this boilerplate code for the various side-data--types makes me
> wonder whether they should not be replaced by something like
> void *av_frame_side_data_alloc(enum AVFrameSideDataType, size_t *size)
> and a corresponding av_frame_create_side_data(AVFrame *frame, enum
> AVFrameSideDataType).
> These functions would return an error in case it doesn't make sense to
> create a side data this way (because there is no struct associated to
> this side data type or because the size of this struct depends upon
> other parameters, too).
>

Why is this side data type allocated, rather than what used to be
the standard, making the side data struct size const? Copy-paste?

Are new fields expected to be added in the future? HDR mastering
metadata is also allocated, but we've never added any fields since
it was merged.
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