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

[James Almer]

On 5/2/2024 7:11 AM, Niklas Haas wrote:
> On Fri, 26 Apr 2024 16:29:03 -0300 James Almer <jamrial at gmail.com> wrote:
>> On 4/26/2024 9:27 AM, Niklas Haas wrote:
>>> From: Niklas Haas <git at 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).
> 
> Do you have a proposed name?
> 
> I can think of:
> - av_frame_side_data_remove_aspect()
> - av_frame_side_data_remove_dependent()
> - av_frame_side_data_remove_category()

No, still one function, but without a reference to something having 
"changed".

Maybe reuse the existing AVSideDataProps enum and add entries that 
define the kind of side data (Like i said above, relevant to color 
properties, dimensions, etc), then add a new function like:

/**
  * Remove and free all side data instances of the given property.
  */
av_frame_remove_side_data_by_prop(AVFrame *frame, enum AVSideDataProps 
prop);

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