[FFmpeg-devel] [PATCH 4/6 v2] avutil/mastering_display_metadata: add a new allocator function that returns a size

[James Almer]

On 3/27/2024 4:41 AM, Anton Khirnov wrote:
> Quoting James Almer (2024-03-25 22:13:25)
>> On 3/25/2024 6:02 PM, Andreas Rheinhardt wrote:
>>> James Almer:
>>>> I don't mind a function like that being added to simplify future
>>>> additions, but this API is orthogonal to the frame side data one. It's
>>>> also used in packets, for example, and right now lavf is using
>>>> sizeof(AVMasteringDisplayMetadata) because
>>>> av_mastering_display_metadata_alloc() is not useful.
>>>>
>>>
>>> The API proposed by me is supposed to make API like
>>> av_mastering_display_metadata_alloc_size() redundant and therefore these
>>> two additions are not orthogonal.
>>
>> Just because there's a frame side data type for MDM does not make the
>> new alloc function redundant.
> 
> The commit message says:
> 
>> av_mastering_display_metadata_alloc() is not useful in scenarios where you need to
>> know the runtime size of AVMasteringDisplayMetadata.
> 
> In what scenarios besides side data do you need to know the size of this
> struct?

None within our libraries that i can think of, but library users can 
have scenarios we need to provide for. MDM is a standalone API, so lets 
not try to make its usability depend on a separate one.
I'm replacing a helper with a better one, it should not be so controversial.