Re: [FFmpeg-devel] [PATCH 1/6] avutil/frame: add av_frame_remove_side_data_changed

[James Almer <jamrial@gmail.com>]

On 4/26/2024 9:27 AM, Niklas Haas wrote:
> From: Niklas Haas <git@haasn.dev>
> 
> Many filters modify certain aspects of frame data, e.g. through resizing
> (vf_*scale* family), color volume mapping (vf_lut*, vf_tonemap*), or
> possibly others.
> 
> When this happens, we should strip all frame side data that will no
> longer be correct/relevant after the operation. For example, changing
> the image size should invalidate AV_FRAME_DATA_PANSCAN because the crop
> window (given in pixels) no longer corresponds to the actual image size.
> For another example, tone-mapping filters (e.g. from HDR to SDR) should
> strip all of the dynamic HDR related metadata.
> 
> Since there are a lot of similar with basically similar operations, it
> make sense to consolidate this stripping logic into a common helper
> function. I decided to put it into libavutil as it may be useful for API
> users as well, who often have their own internal processing and
> filtering.

Maybe instead of "changed", which is a concept that doesn't belong to a 
frame but to a process, use a name that references side data that 
depends on specific properties (dimensions, color props, etc).

Also, don't make it depend on AVFrame, but AVFrameSideData instead, so 
it can be reused in other contexts (Use the av_frame_side_data_* 
namespace for it).

> ---
>   doc/APIchanges      |  3 +++
>   libavutil/frame.c   | 31 +++++++++++++++++++++++++++++++
>   libavutil/frame.h   | 14 ++++++++++++++
>   libavutil/version.h |  2 +-
>   4 files changed, 49 insertions(+), 1 deletion(-)
> 
> diff --git a/doc/APIchanges b/doc/APIchanges
> index 0566fcdcc5..26af725528 100644
> --- a/doc/APIchanges
> +++ b/doc/APIchanges
> @@ -2,6 +2,9 @@ The last version increases of all libraries were on 2024-03-07
>   
>   API changes, most recent first:
>   
> +2024-04-xx - xxxxxxxxxx - lavu 59.17.100 - frame.h
> +  Add av_frame_remove_side_data_changed().
> +
>   2024-04-24 - 8616cfe0890 - lavu 59.16.100 - opt.h
>     Add AV_OPT_SERIALIZE_SEARCH_CHILDREN.
>   
> diff --git a/libavutil/frame.c b/libavutil/frame.c
> index 0775e2abd9..d5482c258e 100644
> --- a/libavutil/frame.c
> +++ b/libavutil/frame.c
> @@ -1015,6 +1015,37 @@ void av_frame_remove_side_data(AVFrame *frame, enum AVFrameSideDataType type)
>       remove_side_data(&frame->side_data, &frame->nb_side_data, type);
>   }
>   
> +static const struct {
> +    enum AVFrameSideDataType type;
> +    int aspect;
> +} side_data_aspects[] = {
> +    { AV_FRAME_DATA_PANSCAN,                    AV_FRAME_CHANGED_SIZE },
> +    { AV_FRAME_DATA_MOTION_VECTORS,             AV_FRAME_CHANGED_SIZE },
> +    { AV_FRAME_DATA_MASTERING_DISPLAY_METADATA, AV_FRAME_CHANGED_COLOR_VOLUME },
> +
> +    { AV_FRAME_DATA_SPHERICAL,                  AV_FRAME_CHANGED_SIZE },
> +    { AV_FRAME_DATA_CONTENT_LIGHT_LEVEL,        AV_FRAME_CHANGED_COLOR_VOLUME },
> +    { AV_FRAME_DATA_ICC_PROFILE,                AV_FRAME_CHANGED_COLOR_VOLUME },
> +    { AV_FRAME_DATA_DYNAMIC_HDR_PLUS,           AV_FRAME_CHANGED_COLOR_VOLUME },
> +    { AV_FRAME_DATA_REGIONS_OF_INTEREST,        AV_FRAME_CHANGED_SIZE },
> +    { AV_FRAME_DATA_DETECTION_BBOXES,           AV_FRAME_CHANGED_SIZE },
> +    { AV_FRAME_DATA_DOVI_RPU_BUFFER,            AV_FRAME_CHANGED_COLOR_VOLUME },
> +    { AV_FRAME_DATA_DOVI_METADATA,              AV_FRAME_CHANGED_COLOR_VOLUME },
> +    { AV_FRAME_DATA_DYNAMIC_HDR_VIVID,          AV_FRAME_CHANGED_COLOR_VOLUME },
> +    { AV_FRAME_DATA_VIDEO_HINT,                 AV_FRAME_CHANGED_SIZE },
> +};
> +
> +void av_frame_remove_side_data_changed(AVFrame *frame, int changed_aspects)
> +{
> +    if (!changed_aspects)
> +        return;
> +
> +    for (int i = 0; i < FF_ARRAY_ELEMS(side_data_aspects); i++) {
> +        if (changed_aspects & side_data_aspects[i].aspect)
> +            av_frame_remove_side_data(frame, side_data_aspects[i].type);
> +    }
> +}
> +
>   const AVSideDataDescriptor *av_frame_side_data_desc(enum AVFrameSideDataType type)
>   {
>       unsigned t = type;
> diff --git a/libavutil/frame.h b/libavutil/frame.h
> index 60bb966f8b..7e07ecf91f 100644
> --- a/libavutil/frame.h
> +++ b/libavutil/frame.h
> @@ -983,6 +983,20 @@ AVFrameSideData *av_frame_get_side_data(const AVFrame *frame,
>    */
>   void av_frame_remove_side_data(AVFrame *frame, enum AVFrameSideDataType type);
>   
> +/**
> + * Flags for stripping side data based on changed aspects.
> + */
> +enum {
> +    /* Video only */
> +    AV_FRAME_CHANGED_SIZE           = 1 << 0, ///< changed dimensions / crop
> +    AV_FRAME_CHANGED_COLOR_VOLUME   = 1 << 1, ///< changed color volume
> +};
> +
> +/**
> + * Remove all relevant side data after a corresponding change to the frame
> + * data, based on the given bitset of frame aspects.
> + */
> +void av_frame_remove_side_data_changed(AVFrame *frame, int changed_aspects);
>   
>   /**
>    * Flags for frame cropping.
> diff --git a/libavutil/version.h b/libavutil/version.h
> index ea289c406f..3b5a2e7aaa 100644
> --- a/libavutil/version.h
> +++ b/libavutil/version.h
> @@ -79,7 +79,7 @@
>    */
>   
>   #define LIBAVUTIL_VERSION_MAJOR  59
> -#define LIBAVUTIL_VERSION_MINOR  16
> +#define LIBAVUTIL_VERSION_MINOR  17
>   #define LIBAVUTIL_VERSION_MICRO 100
>   
>   #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
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