[FFmpeg-devel] [PATCH 3/4] vf_tonemap_opencl: Move update_metadata() to a shared file

[James Almer]

On 7/25/2018 12:46 PM, Vittorio Giovara wrote:
> ---
>  libavfilter/colorspace.c        | 17 +++++++++++++++++
>  libavfilter/colorspace.h        |  1 +
>  libavfilter/vf_tonemap_opencl.c | 19 +------------------
>  3 files changed, 19 insertions(+), 18 deletions(-)
> 
> diff --git a/libavfilter/colorspace.c b/libavfilter/colorspace.c
> index d6f6055401..c6682216d6 100644
> --- a/libavfilter/colorspace.c
> +++ b/libavfilter/colorspace.c
> @@ -118,3 +118,20 @@ double ff_determine_signal_peak(AVFrame *in)
>  
>      return peak;
>  }
> +
> +void ff_update_hdr_metadata(AVFrame *in, double peak)
> +{
> +    AVFrameSideData *sd = av_frame_get_side_data(in, AV_FRAME_DATA_CONTENT_LIGHT_LEVEL);
> +
> +    if (sd) {
> +        AVContentLightMetadata *clm = (AVContentLightMetadata *)sd->data;
> +        clm->MaxCLL = (unsigned)(peak * REFERENCE_WHITE);
> +    }
> +
> +    sd = av_frame_get_side_data(in, AV_FRAME_DATA_MASTERING_DISPLAY_METADATA);
> +    if (sd) {
> +        AVMasteringDisplayMetadata *metadata = (AVMasteringDisplayMetadata *)sd->data;
> +        if (metadata->has_luminance)
> +            metadata->max_luminance = av_d2q(peak * REFERENCE_WHITE, 10000);
> +    }
Frame side data is refcounted, so this is not correct. I'm not sure if a
side data element is ever modified in-place long after being created to
being with, aside from this function here.

Easiest option is to call av_buffer_make_writable() on sd->buf and
updating the sd->data pointer before modifying the fields in question,
but such manual handling of side data seems improper and fragile.
I guess another option is av_mastering_display_metadata_alloc(), copy
the values, av_frame_remove_side_data(), av_buffer_create(), then
av_frame_new_side_data_from_buf().

Honestly, i think we may have to add a make_writable() function for side
data for this.